Poultry industry has emerged as the most dynamic and fastest expanding segment in animal husbandry sector with an annual growth rate of 6% in 1980's, 11% in 1990s, 19% in 1997-2002 and 6.2% during 2002-2006 in broiler chickens and 5-6% in egg production during this period in India. With an annual production (BAHS, 2010) of around 61.45 billion eggs (95.2% hen, 2.5% duck and 2.3% from other species) and 2.03 million metric tonnes of poultry meat, India ranks third and fifth in egg and meat production, respectively, in the world. The estimated poultry population in 2007 was 648.8 million comprising 617.7 million fowls, 27.6 million ducks and 3.5 million other poultry birds such as Japanese quails, turkeys, guinea fowl, emu, etc. (BAHS, 2010). The performance of birds in terms of meat and egg production has also improved. Feed is the major input (65 to 80%), feed-cost is the major constraint but a major mean for manipulating production cost and making the enterprise profitable.
However, in recent years poultry industry has crippled many times due to rising cost of feeds and emergence of new or re-emerging of existing diseases causing severe morbidity, mortality and economic loss. Immuno-suppression and incidences of mycotoxicoses are frequently encountered. About 25% of world’s cereals are contaminated with known mycotoxins. Mycotoxins cause a great loss by lowering the production performance, immunity and health, and through increasing stress and mortality in birds. Impact of globalization on poultry industry has increased the competitiveness for marketing the safe and quality poultry products in world as well as in domestic market. Safe foods can only be achieved though feeding of safe feed. Presence of mycotoxins in feed is one of the major constraints in exploiting the utilization of inherent nutritional intrinsic factors efficiently resulting in increased feed requirement and thus increased feed cost of production. Moreover, immuno-suppression leads to more pre-harvest losses in terms of morbidity and mortality even at very low concentration, which further increases the cost of production. Therefore, it is needed to understand mycotoxins and their genesis in feeds, and to realize consequences and effective management practices to get rid of from their hazards.
Mycotoxins are low molecular weight secondary metabolites produced by certain strains of filamentous fungi such as Aspergillus, Penicillium and Fusarium, which invade crops in the field and may grow on foods during storage under favaourable conditions of temperature and humidity. The occurrence of mycotoxins in agricultural commodities depends on region, season and the conditions under which particular crop is grown, harvested or stored. Although several hundred mycotoxins are known, the mycotoxins of most concern based on their occurrence and toxicity are aflatoxins, ochratoxin A, trichothecenes, zearalenone, fumonisin and moniliformin. The presence of mycotoxins in commodities is presently unavoidable and, therefore, to avoid their occurrence in the food chain requires management strategies that would prevent contaminated commodities from entering food and feed processing facilities. Various methods to decrease or eliminate mycotoxins are being studied and several approaches such as physical methods of separation and detoxification, biological and chemical inactivation, and decreasing bioavailability to host animals are being used and/or investigated.
Mould growth and feed quality: Mould infection of crops (feedstuffs) can occur in the field, during harvesting, drying, storage and during processing. Similarly, mycotoxin production can occur at one or all of these stages. Mould can cause problem in two ways. First, the mould itself will use the protein, carbohydrate and fat from the feed for its own development thus, reducing the nutritive value of the feedstuffs. Badly contaminated maize may lose 10% of its metabolizable energy and 5% of its protein. In addition, the palatability is also reduced. Secondly, the moulds produce mycotoxins. The major mycotoxin producing genera are Aspergillus, Fusarium and Penicillium. Many species of these fungi produce mycotoxins in feeds. These mycotoxins reduced production in terms of body weight and egg production, decreased feed conversion efficiency etc. and livability through pathological changes in different organs and reducing disease resistant capacity. Mycotoxin producing fungi are divided into two groups:
a. Field fungi: Field fungi invade the grains while the crop is in the field (occurring prior to harvest) and usually require high moisture conditions. e.g. Fusarium and Alternaria spp.
b. Storage fungi: Storage fungi invade the grains during storage and require less moisture than field fungi, and do not present any serious problem before harvest. e.g. Aspergillus and Penicillium spp.
Mycotoxin producing fungi are mostly ubiquitous in nature. The mould infestation of the feedstuffs has a great negative impact on the quality of feed. The physical signs of mould occurrence in animal feeds are dustiness, poor flow out of grain bins, feed refusal by animals, mouldy and musty smell, and darkening of grain.
Factors affecting development of fungi and mycotoxin production
a) Physical factors: Humidity, temperature, microflora zones and physical integrity of the grains
b) Chemical factors: pH, composition of the substrate and mineral nutrients
c) Biological factors: Presence of insects and specific strains
The water content in the atmosphere and substrate is one of the most important factors for the development of fungi and the production of Mycotoxins. However, not only does the quantity of water present influence the development of these fungi, but also the state in which the water is present, either as free water or combined water. Free water exists within and around vegetable tissues or their cells and can be eliminated without seriously interfering with vital processes. Combined water is present in vegetable and animal tissue bound with proteins and carbohydrate, forming an integral part of the cells that compose the tissues.
Commonly contaminated feeds are:
Energy supplements: Maize, oats, barley, wheat, rice, millets, rice polish, wheat meal and wheat grits.
Protein supplements: Groundnut cake, cottonseed meal, maize gluten meal, coconut meal, sesame cake, sunflower meal and soybean meal. Deep caked litter, unclean feeders and waterers also encourage mycotoxin production.
Factors affecting the toxicity of mycotoxins in birds
(a) Avian species, breed and strain
(b) Mycotoxin concentration in the feed
(c) Duration of exposure to the bird ingesting the mycotoxin contaminated feed
(d) Health and nutritional status of the bird
(e) Age of the bird
(f) Habitat in which the bird is kept
(g) Presence of more than one mycotoxins in feed
Mycotoxins affecting poultry: Mycotoxins are of great concern as they possess a permanent challenge for the poultry industry because they are widely present in feedstuffs around the world and affect animal production even in very low concentrations. Mycotoxins produce severe economic losses in the poultry industry. Economic losses associated with mycotoxicosis are stunted growth, reduced egg production, reduced feed conversion efficiency, poor egg shell quality, increased mortality, damaging gut health, reduced fertility, leg problems, carcass condemnation, increased susceptibility to diseases. Adverse effects on the gastro-intestinal tract are probably the major cause of economic losses resulting from trichothecene. T-2 toxin can cause caustic injury to the mucosa, destroying cells on the tips of villi, and affect rapidly dividing crypt epithelium. Histopathology of GI tract lesions due to acute intoxication by purified T-2 toxin is characterized by hemorrhage, necrosis, and inflammation of the intestinal epithelium, which occur before transient shortening of villi and reduction in the mitotic activity in crypt epithelium. Necrosis also occurs in the mucosa of the proventriculus and gizzard.
Cellular interference of Mycotoxins
Mycotoxins exhibit a diversity of biochemical and cellular mechanisms of toxicity. To understand the interference at cellular level and intercalation with the toxicity of other mycotoxins with the cellular machinery, understanding of mechanism on toxic compounds in altering behavior of the molecules of life is needed.
Probable primary biochemical lesions and the early cellular events in the cascade of cellular events leading to toxic cell injury or cellular deregulation of some Mycotoxins:
Economic losses due to mycotoxicosis: The economic losses associated with mycotoxicoses include poor growth, reduced egg production, reduced feed conversion, increased morbidity and mortality, carcass condemnation poor egg shell quality, reduced fertility, leg problems and increased susceptibility to disease. However, the degree of losses depends upon the concentration, type and interaction of mycotoxins as well as the nutritional plane of the birds. A brief description of the most important mycotoxins posing threat to poultry industry is given below:
Aflatoxins: The word “Aflatoxin” is derived as: A+ fla+ toxin, where A stands for Aspergillus, fla for flavus and toxin for poison. Aflatoxins are a group of closely related toxic substances produced by some fungi, especially Aspergillus flavus, Aspergillus parasiticus and Aspergillus nomius. There are four main types of naturally occurring aflatoxins i.e. B1, B2; which give blue fluorescence under ultra-violet light at first and second Rf value, respectively, and G1 and G2 which give green fluorescence under ultra-violet light at first and second Rf value, respectively. Aflatoxins differ significantly in their relative toxicity. The toxic nature of aflatoxin is due to its chemical structure. Aflatoxin B1 (AFB1) is the most toxic compound. By and large, the toxigenicity among four aflatoxin compounds has been rated in the following order: B1≥G1≥B2≥G2. Extensive studies have been conducted in various avian species. Aflatoxicosis reduces the ability of the bird to digest protein and absorb amino acids. Aflatoxins reduce the ability to synthesize DNA, RNA and ribosome protein and thus hepatic amino acids retention increases. As a result aflatoxins reduce the protein synthesis and increase the protein requirement of the bird. Therefore, the birds with low protein suffer more in terms of body weight gain, immunity and egg production than those fed with high level of protein in diet. Thus, increase in CP content of the diet is an ameliorating measure of growth suppression in birds fed with aflatoxins. AFB1 exposure through feed increases the susceptibility of birds to coccidiosis and decreases the effectiveness of anticoccidial drugs. Reports indicate increased incidences of salmonellosis and candidiasis when different levels of aflatoxins were fed to chickens.
Toxicity of aflatoxins: Aflatoxins are highly toxic compounds. The liver is the main organ affected, followed by the kidneys. They cause hepatic changes leading to serious liver damage characterized by haemorrhages, cirrhosis and fatty degeneration of the liver. However, pancreas, gall bladder, lung and gut may also be affected.
Aflatoxins are absorbed from the gut and are transported to the liver where they are metabolized. Aflatoxin B1 may be transformed to aflatoxin M1, representing a detoxification, since aflatoxin M1 is less active than aflatoxin B1. However, the common metabolic process is diol formation at the double bond of the furan ring, a very toxic species. The resultant aflatoxin B1-2,3-diol is much more toxic then aflatoxin B1 itself. Among the naturally occurring aflatoxins, AFB1 is the most acutely toxic followed by AFG1, AFB2 and AFG2. This is shown by LD50 values of one-day old ducklings. While the LD50 of aflatoxin B1 is 0.36 mg/kg, the corresponding value of aflatoxin B2 is five times higher, with this compound containing a saturated furan ring. This shows that the unsaturated furan moiety has an important effect on acute toxicity. On comparing the LD50 value of aflatoxin G1 with that of aflatoxin B1, where the cyclopentanone ring has been converted in the former compound in to a six-membered lactone ring, aflatoxin G1 is considerably less potent (0.78 mg/kg). Therefore, the cyclopentanone ring is of lesser importance for the mediation of acute toxicity. The toxicity of aflatoxins G1,B2 and G2 is approximately 50, 20 and 10%, respectively that of aflatoxin B1 when tested against various animal species and mammalian cells in culture.
Mechanism of aflatoxin toxicity: The mechanism of aflatoxins has received wide attention (Patterson, 1977; Eaton and Gallagher, 1994; Do and Choi, 2007). The difference regarding sensitivity of various animal species towards AFB1 is thought to be linked with differential state of its metabolism and the types of metabolites formed. Besides being the primary organ of AFB1 accumulation and metabolism, liver is also the main site where AFB1 is metabolized and where the metabolites bind with nucleic acids and proteins. Kidneys also take part in detoxification of aflatoxins and are also among the organs where most of the aflatoxin residues are detected. Cytochrome P450 enzymes (CYP) (including CYP1A2, CYP3A4 and CYP2A6) in the liver and other tissues convert AFB1 to epoxides (AFB1-8,9-exo-epoxide, and AFB1-8,9-endo-epoxide), and to AFM1, AFP1, AFQ1, and its reduced form aflatoxicol. Of the epoxides, the AFB1-8,9-exo-epoxide (and not the AFB1-8,9-endo-epoxide) can form covalent bonds with DNA and serum albumin resulting in AFB1-N7-guanine and lysine adducts, respectively. Like AFB1, AFM1 can also be activated to form AFM1-8,9- epoxide that binds to DNA resulting in AFM1-N7-guanine adducts. These guanine and lysine adducts have been noted to appear in urine.
The metabolites AFP1, AFQ1, and aflatoxicol are thought to be inactive and are excreted as such in urine, or in the form of glucuronyl conjugates from bile in feces. In case of chicken exposed to AFB1 contaminated rations, AFB1, AFM1, and aflatoxicol have been detected in liver, kidneys, and thigh muscles (Micco et al., 1988). Besides these, AFB2a has also been detected in livers of both broilers and layers on a ration contaminated with a mixture of aflatoxins (AFB1 80%; AFB2 2.6%; AFG1 16.8%; and AFG2 0.1%) (Fernandez et al., 1984). Recent studies (Diaz et al., 2010) have shown that CYP2A6 and to a lesser extent YP1A1 are responsible for bio-activation of AFB1 into epoxide form in the liver of chicken and quail. More data are, however, needed to fully understand the differences in metabolism of chicken with species which are comparatively more sensitive to AFB1.
Clinical signs of aflatoxin toxicity: The clinical signs are decreased weight gain as well as loss in body weight, anorexia, decreased egg production, reduced feed conversion efficiency, increased morbidity and mortality, immune suppression and increased disease susceptibility, reduced fertility and hatchability, embryo toxicity, specific visceral haemorrhage, increased susceptibility to environmental and microbial stressors, leg weakness and reduced bone strength, pale shank, wattles and combs, thinning of thigh muscles, black oily and sticky excreta, and increased incidence of bruising and downgrading. The post-mortem lesions include fatty liver (white spots on liver), liver necrosis, bile duct hyperplasia and enlarged kidney.
Chickens: Aflatoxins are potent hepatotoxic, nephrotoxic and immunosuppressive. The important signs in young birds are less feed intake (anorexia), reduced body weight gain and feed utilization efficiency, listlessness, lameness, convulsion, dehydration of combs and shanks, jaundice, and pigmentation. In layers, the signs are reduction in egg production, egg weight and feed efficiency; poor hatchability and internal egg quality. The gross pathological changes in broilers suffering from aflatoxicosis include enlarged fragile liver with pale discolouration and haemorrhagic spots on surface, nephritis with congestion and necrotic foci on kidney, enlarged spleen (spleenomegaly) with haemorrhagic spots, enlarged pancreas and regression of bursa of Fabricius. Histological lesions are vacuolization of the hepatocytes with infiltration of fat.
Ducks: Ducklings are the most vulnerable to aflatoxins and even toxicity may occur at 30ppb of aflatoxin level. One to seven day old ducklings, when given feed containing 300 to 600 ppb of AFB1 for 7 to 14 days, had serious hepatic lesions and significant death rate. Aflatoxicosis in ducks results in delay in development, hyperkeratosis of the cornea and the oral mucosa, malformations and bone fragility, leg paralysis, inflammatory edema of the eyelids, dermatitis, scarce feathering, and enlarged, fatty, pale and friable liver.
Turkeys: Day-old turkey poults given feed containing a concentration of 100 to 800 ppb of AFB1 for a period of 35 days resulted in a significant reduction in body weight gain and had hepatic lesions. A 0.5 ppm concentration of AFB1 significantly reduced the efficiency of the vaccine used against Marek’s Disease.
Effects of aflatoxin B1 on gastrointestinal tract: Gastrointestinal tract is the main site where conversion and absorption of food components takes place i.e. the organ for supply. Gastrointestinal tract is the first organ coming into contact with mycotoxins of dietary origin and should be expected to be affected by AFB1 with greater potency as compared to other organs. However, this aspect of aflatoxicosis is the often neglected area of mycotoxin research and available literature is non-conclusive. Feeding of AFB1 contaminated (1mg/kg) diet for 4 weeks resulted in catarrhal enteritis with lymphocytic or mononuclear cell infiltrations in the intestine of broilers (Kumar and balachandran, 2009). Aflatoxin contaminated diet resulted in a linear increase in the crypt depth in distal jejunum with the increasing levels of AFB1 in the diet as 0, 0.6, 1.2, and 2.5 mg/kg, but no effect of the toxin on villus height and number of goblet cells (Applegate et al., 2009). Feeding of 1.25 to 5 mg AFB1/kg diet for 3 weeks has no effect on in vitro absorption of glucose and methionine in the intestine of broilers (Ruff and Wyatt, 1976). However, a high dose of 10 mg AFB1/kg diet, for more than 1 week, increased both the mediated and diffusion components of glucose and methionine absorption. At 0.6 and 1.2 mg AFB1/kg diet, the apparent metabolizable energy (AME) was found to be reduced in chicken (Applegate et al., 2009).
Ochratoxin A: The term “Ochratoxin” was derived from the name of the mould: Aspergillus ochraceous. From which the ochratoxins were first isolated. Ochratoxins are produced by several species of Aspergillus (Aspergillus ochraceous) and Penicillium (Penicillium viridicatum). There are 7 types of ochratoxins of which ochratoxin A (OTA) is the most toxic. Ochratoxin A is chemically defined as 7- carboxyl-5-chloro-8-hydroxyl 3, 4-dihydro-3-R-methyl isocoumarin linked to L-β-phenylalanine. The main effect produced by ochratoxin is nephrotoxicity but can also produce a liver disorder which produces an accumulation of glycogen in hepatic and muscular tissue. The signs are dehydration, emaciation, dry gizzard, bleeding in mucosa of proventriculus and catarrhal enteritis in young chicks. A significant reduction in egg production and increase in egg shell elasticity are seen in laying hens when the diets contain 3 ppm or more ochratoxins. Chicks died of ochratoxicosis show white flake like deposits in kidneys, ureters, heart, pericardium, liver and spleen as observed in visceral gout.
Clinical signs of ochratoxin toxicity: The signs include reduced feed intake, reduced growth rate and egg production, reduced feed conversion efficiency, mortality due to acute renal failure, poor egg shell quality and higher incidence of eggs with blood spots, reduced embryo viability and decreased hatchability, reduced feathering, polyurea with large volumes of wet faeces. The post mortem lesions are pale and grossly enlarged kidney, fatty liver, urate deposition in joints and abdominal cavity (at high exposure levels), depletion of lymphocytes and with it strong suppression of cellular immunity thus enhanced susceptibility to viral infection.
Chickens: One-day-old chicks given feed containing 0.2 to 1.6 ppm of OTA during a period of 2 to 3 weeks had delayed development and reduction of live weight. One-day-old White Leghorn chicks exposed to diet with 0.3 to 1.0 ppm of OTA or 26 week old White Leghorn laying hens given feed containing 0.5 to 4.0 ppm of OTA, for a period of 341 and 42 days, respectively had serious renal lesions, microscopic changes and histological alterations in the liver in chicks and a decrease in egg production, egg weight, feed intake and body weight in laying hens. White Leghorn laying hens fed diet with 0.5 to 1.0 ppm of OTA had a significant decrease in egg production, strained egg shells and increased levels of uric acid in their serum.
Ducks: Khaki Campbell ducks, given a diet containing 2.0 ppm of OTA from birth until 18 days of age, suffered from delayed growth, enlarged livers and kidneys and regression of the thymus. Microscopic observations showed an accumulation of glycogen in the liver and an infiltration of lymphoid cells in the kidneys.
Turkeys: Turkey’s poults fed with diets containing 1.0 to 8.0 ppm of OTA from birth until 3 weeks of age suffered from delayed development, reduction in water intake, decreased feed utilization efficiency, enlargement of the proventriculus and gizzard; a regression of the thymus, an increase of uric acid in plasma, serious osteoporosis and death.
Trichothecenes: The trichothecenes (TCT), the mycotoxins, occur worldwide in grains and other commodities. The TCT mycotoxins are mainly produced by Fusarium graminearum, F. episphaeria, F. lateritium, F. nivale, F.oxysporum, F. poae F. rigidiusculum, F. roseum, F. solani, F. sporotrichoides, and Fusarium tricinctum. TCT are also produced by Calonectria nivalis, Cephalosporium crotocigenum, Gibrella saubinetti, Mycotecium verrucaria, Stachybotrys atra, Trichoderma viride and Tricotecium roseum. Toxin production is greatest at high humidity and at temperatures of 6 to 24ºC. The name trichothecenes was derived from the skeletal tetracycline in their molecule, 12, 13-epoxyitricotec-9- eno. TCT are divided into two groups, macrocyclical and non- macrocyclical. Trichothecenes non- macrocyclical mycotoxins are divided into two groups, A and B. The A group are more toxic to poultry than B group. Some mycotoxins included in group A are: T-2 toxin, Diacetoxyscirpenol (DAS), triacetoxyscirpenol (TAS), escirpentriol (STO), and HT-2 toxin. Mycotoxins included in group B are fusarenone-X, Vomitoxin or deoxynivalenol (DON), and Nivalenol (NIV). TCT contain an epoxide at the C 12, 13 positions, responsible for their toxicological activity. TCT mycotoxins are potent cytotoxins. These mycotoxins inhibit the protein synthesis followed by an interruption of DNA and RNA synthesis.
The main effect of trichothecenes toxins is gastro-enteric, but also affecting the digestive, the nerves, and the circulatory system, as well as the skin. It is characteristic of Vomitoxin to induce vomiting and rejection of food in some animals species. In general way the toxicological characteristics of these mycotoxins (depends on the animal species) include: vomiting, irregular heartbeats, and diarrhea; hemorrhaging, edemas, cutaneous tissue necrosis; hemorrhaging of the stomach and intestinal epithelial mucosa; destruction of hematopoietic tissues; decrease of white blood cells and circulating platelets; hemorrhaging meninges (cerebral); alteration of the central nervous system; rejection of food; necrotic lesions on different parts of the mouth; pathological deterioration of bone marrow, lymphatic nodules, and intestinal cells.
Clinical signs of trichothecenes toxicity: Oral lesions (circumscribed proliferate yellow caseous plaques occurring at the margin of the beak, mucosa of the hard plate and the angle between the mouth and the tongue), reduced feed intake, reduced weight gain and egg production, poor shell quality, reduced female fertility and hatchability of fertile eggs, immune suppression, reduced vaccination response, Tibia dyschondroplasia, gizzard erosion, necrosis of proventricular mucosa, regression of ovaries and increased liver weight.
T-2 toxin: It is the most important trichothecene mycotoxin and impact of T-2 Toxin in different poultry species is given below:
Chickens: Day-old chicks fed diets containing 0.4 ppm of T-2 toxin for a period of 49 to 63 days developed oral lesions and had decreased body weight gain. Higher doses (4.0 to 16.0 ppm) to day-old chicks for a period of 21 days resulted in oral lesions (lesions on their palates and tongues), high mortality rate (evident on the 7th day of ingestion), necrotic lesions in the gizzard, an increased rate of liver hematomas, higher relative spleen and pancreas weight and reduced weight of the bursa of Fabricius decreased. Oral lesions are characterized by a proliferation of caseous yellowish- white plaques around the beak, palate mucosa, mouth and tongue; tissue inflammation and localized necrosis. Externally the oral lesions are fibrinous and soft, while in the interior an infiltration of granular leukocyte.
Feed containing T-2 toxin (1.0, 5.0 and 10.0 ppm), given to hens for a period of 28 days, resulted in a decrease in egg production in dose dependant manner, feed intake, egg shell thickness, fertility and hatchability. Just 24 hours after consuming a feed containing 2.0 ppm of T-2 toxin, laying hens may experience harmful effects including oral lesions affecting the palates, tongue and beak; a reduction in feed intake and a decrease in egg production.
Ducks: Day-old Muscovy ducklings (Cairina moshata) when fed diet containing 0.25 to 1.0 ppm of T-2 toxin suffered from oral lesions after 16 hours of consumption of feed. Feed containing T-2 toxin level at 2.0 ppm when given to 6 week-old ducks for a total of 9 days, the ducks developed significant ulceration and erosion of the esophagus and the oral cavity. There was also a decrease in body weight, thymus weight, spleen weight and bursa weight.
Turkeys: Young turkeys given feed containing 1.0 ppm of T-2 toxin for a period of 32 more days did not have any alterations in their development, weight gain, small intestinal morphology or antibody production when compared with the control group. However, when the 1.0 ppm T-2 toxin contamination was in combination with 1.0 ppm diacetoxyscirpenol contamination, young turkeys had serious and evident oral lesions 7 to 15 days after ingesting the contaminated feed. There were moderate morphological changes in the small intestine, without pathological and/or histopathological lesions.
Deoxynivalenol (DON) or Vomitoxin: Feeding contaminated feed with 50 ppm DON to 6 days old chicks for a period of 6 days caused few oral lesions. However, no oral lesions were observed when 15 ppm DON was fed for 42 days. DON at 350 to 700 ppb in feed resulted in decreased egg weight and an increase of soft shelled eggs in laying hens. Breeder exposed to DON (2.5 and 4.9 ppm) for 10 weeks resulted in significant anomalies in the development progenies characterized by weak chicks. Feeding of contaminated diet with 20 ppm DON to day-old turkey poults had no adverse effect in feed intake, body weight gain and histology. Similarly, wheat containing 5.8 ppm DON when fed to wild ducks, in captivity for a period of 14 days, resulted in no wheat refusal. There was no difference in levels of serum protein, calcium, glucose, creatinine kinase, aspartate aminotransferase and uric acid. Body weight and certain organ weight were similar to ducks fed on non-contaminated feed.
Nivalenol (NIV): Seven days old male broiler chickens exposed to different doses (6 and 12 ppm in diet) of NIV exhibited reduced feed intake, feed conversion efficiency and body weight gain. There were incidences of gizzard erosions at 3 to 12 ppm and reduced liver weight at 6 and 12 ppm NIV. Feeding NIV 1 to 5 ppm for 7 weeks to White Leghorn of 55 weeks age suffered from reduced feed intake but there was no apparent effect on body weight, egg production and egg quality. Pathological examination revealed gizzard lesions, haemorrhages in the duodenum and swollen cloaca and oviduct with immature eggs at 3 and 5 ppm levels of NIV.
Monoacetoxyscirpenol (MAS): The LD50 value of 15-MAS as single oral dose in day-old chicks is 3.4 mg/kg body weight. The toxicity of 15-MAS was higher than 3- and 4-MAS whose LD50 values were 8.1 and 9.6 mg/kg body weight, respectively. Feed contaminated with 0.5 ppm MAS fed to day-old chicks for 21 days, resulted in oral lesions within 7 days and produced feather abnormality like frayed feathers and lack of plumage network. Significant growth depression is observed at 2 ppm level of contamination. Decreased feed consumption, body weight and egg production are reported when the layers were exposed to 25 and 50 ppm MAS for 28 days.
Diacetoxyscirpenol (DAS): Feed contaminated with 1 to 2 ppm DAS given to day- old chicks for 3 weeks caused oral lesions and delayed development. Laying hens exposed to 2 ppm DAS had decreased feed intake and egg production, oral lesions affecting palate, tongue and beak. Administration of 0.5 ppm of DAS to 50 week- old hens for one month resulted in decreased hatchability of fertile eggs. Day- old Muscovy ducklings exposed to diet with 0.25, 0.50 and 1.0 ppm of DAS for 7 days had oral lesions 16 hours after DAS feeding. DAS containing (1ppm) feed fed to young turkeys for 32 days showed no effect on weight gain, small intestine morphology and antibody production. However, when 1 ppm DAS was combined with 1 ppm T-2 toxin, oral lesions and morphological changes in small intestine were observed.
There are two different arguments that explain oral lesions produced by T-2 toxin and diacetoxiscirpenol. The first argues that the contaminated feed adheres primarily to the oral region due to the high moisture in this area. Given that these mycotoxin are extremely alkaline, this alkalinity provokes the oral lesions. The second argues that after absorption of these mycotoxins through the gastrointestinal tract, they are eliminated through the animal’s saliva. Again, the alkalinity of said mycotoxins produces the oral lesions.
Triacetoxyscirpenol (TAS): LD50 value of TAS as single oral dose in day-old chicks is 7.2 mg/kg body weight. TAS (4ppm) contaminated diet fed to day-old chicks for 21 days caused oral lesions within a week. The number of lesions increased with the increase of exposure period. TAS (8 ppm) containing feed resulted in a significant growth depression in broilers.
Escirpentriol (STO): The LD50 values of STO as one oral dose in day-old chicks is 9.3 mg/kg body weight. Dietary exposure of 2 ppm STO to day-old chicks for 21 days resulted in oral lesions, feather abnormality and significant reduction in growth.
Citrinin: Citrinin is produced by several species of genus Penicillium and Aspergillus but it is chiefly produced by Penicillium citrinum, Penicillium expansum and Penicillium verrucosum. Citrinin toxicity symptoms include reduced growth, decreased feed consumption and feed conversion. It is a nephrotoxin and like ochratoxin. It causes necrosis of tubual epithelial cells in the kidney, and in some cases, hepatoxicity. Necropsy of birds with citrinin toxicity revealed the presence of pale and swollen kidneys. Increase in the size of liver and kidney is also reported. One of the symptoms of citrinin toxicity in poultry is increase in the amount of water consumption followed by diarrhea. Generally, the incidence of citrinin toxicity is low. No adverse effects on the performance were reported when feed containing 100 ppm citrinin was fed to broiler chickens.
Zearalenone (ZEN or F-2 toxin): Zearalenone, a non-steroidal estrogenic mycotoxin naturally found in maize, barley, wheat, oats and sorghum, is produced by several species and subspecies of Fusarium due to high humidity at low temperatures (10 to 15ºC). ZEN is mainly produced by Fusarium roseum, F. tricinctum, F. Graminearum, F. oxysporum and F. moniliforme. Fusarium graminearum requires a minimum of 22 to 25% moisture to grow in cereal grains. Zearalenone is the generic name for [6-(10-hydroxyl-6-oxo-trans-1- undecenyl) –β- resorcylic acid lactone]. The term zearalenone has been derived from the name of the host plant maize (Zea) infected by Fusarium and partly from its chemical nature (ral from resorcylic acid lactone, en = double bond at C-1-2, and one = ketone). ZEN is accumulated mainly in the liver and gall bladder, and excreted mainly in faeces as ZEN and α- and β zearalenol. In layers, most part is excreted in faeces; however, residues may occur in yolk. A concentration of 59 to 103 ppb in muscle and up to 681 ppb ZEN in liver was detected in chickens fed with 100 ppm dietary ZEN for 8 days.
Clinical signs of zearalenone toxicity: At high concentrations the symptoms observed include vent enlargement and enhanced secondary sex characteristics. Feed contaminated with 300 to 600 ppm ZEN, given to chicks for 4 days, resulted in enlargement of the bursa of Fabricius and an increase of cysts in the genital tract. No effect on weight gain, feed intake or feed conversion efficiency was observed when ZEN contaminated feed (10 – 800 ppm) was fed to day-old chicks for 21 days. No marked lesions were recorded on postmortem study except for hypertrophy of the oviduct in some birds exposed to 800 ppm ZEN. Feed contaminated with ZEN (50 – 800 ppm) fed to broiler chickens (6 to 9 weeks old) resulted in no difference in performance, blood parameters and relative weight of organ. Laying hens are also quite resistant to ZEN since no complication was recorded after consuming feed containing 25 and 100 ppm of ZEN to 20 and 42 week- old White Leghorn hens for a period of 17 and 7 weeks, respectively. Consumption of 100 ppm ZEN contaminated feed showed no effect on egg production and fertility in mature geese. Mature male and female chickens fed with dietary ZEN (800 ppm) depicted no effect on reproductive performance. No effect on egg production, egg shell thickness, egg size, fertility, hatchability, feed consumption, body weight and relative weight of comb, oviduct, heart, liver and spleen was observed. Turkeys fed on 300 ppm ZEN contaminated feed developed enlarged vents within four days, however, no other gross complication was observed.
Poultry is found to be less susceptible to the estrogenic effects of ZEN. At large concentrations in feed, the ill effects of ZEN in poultry may include vent enlargement and secondary sex characteristics. Although, poultry appear to be resistant to the toxic effects of ZEN, its detection in poultry feed is suggested to be used as a biomarker for unknown Fusarium toxins.
Fumonisin: Fumonisins are predominantly produced by Fusarium moniliforme. There are 6 types of Fumonisins viz. B1, B2, B3, B4, A1 and A2. However, Fumonisins B1 (FB1) and Fumonisins B2 (FB2) are the most prominent and potent toxic. These mycotoxins inhibit the synthesis of lipoproteins sphingolipids (sphinganine and sphingosine), structural component of nervous system.
Clinical signs of fumonisin toxicity: Spiking mortality (paralysis, extended legs and neck, wobbly gait, gasping, reduced growth, increased organ weights, hepatocellular hyperplasia, poor vaccination response and increased liver sphinganine: sphingosine ratio. FB1 (10 to 525 ppm) contaminated diet fed to two day-old chicks for a period of 6 to 21 days showed a decrease in body weight and absolute weight of liver, spleen and bursa of Fabricius. Variations in the level of free sphinganine and the relationship between sphinganine/ sphingosine were observed. In another study, FB1 levels at 100 to 400 ppm were detrimental to the performance in juvenile chicks. Birds fed on 450 and 525 ppm FB1 contaminated feed showed a significant decrease in weight gain and feed conversion, increased kidney and liver weight and increased hemoglobin concentration. Increased serum level of sphinganine and sphingosine were also observed. Due to inhibition of sphingolipids biosynthesis by fumonisin, it was suggested that feed containing more than 75 ppm FB1 can be toxic to chicks. Broilers fed on 80 ppm FB1 contaminated feed from 1 to 21 days of age exhibited no adverse effect on weight gain and feed conversion. Reduced body weight and mortality were reported in a dose dependent manner in chickens fed on diet containing 125 or 274 ppm FB1. Feed containing 200 or 300 ppm FB1 fed to day-old chicks for 3 days resulted in thymic cortical atrophy, multifocal hepatic necrosis, biliary hyperplasia and widening of the proliferating cartilage zone in proximal tibiotarsal physes. Increased sphinganine: sphingosine ratio was reported in chicks exposed to various concentrations (89, 190, 283, 289, 481, 592 and 681 ppm) of FB1 for 3 weeks. FB1 at 289 ppm or higher levels resulted in isolated foci of hepatic necrosis with a mild heterophil and macrophage infiltration, moderate diffuse hepatocellular hyperplasia, mild biliary hyperplasia and moderate to severe periportal granulocytic cell proliferation.
White pekin ducks (day-old) fed on FB1 (100, 200 and 400 ppm) contaminated diet suffered from reduced weight gain and feed intake, and increased absolute weight of liver, heart, kidney, pancreas and proventriculus. The relationship between sphinganine and sphingosine increased significantly. Mild to moderate hepatocelluler hyperplasia was also observed.
Feed contaminated with FB1 (25 and 50 ppm) fed to one week old turkeys resulted in a significant reduction in feed intake and increased relationship between sphinganine/ sphingosina at 50 ppm level, however, 25 ppm level did not produce any relevant problems. FB1 at 200 ppm concentration in diet fed to day-old turkeys for 2 to 3 weeks resulted in lack of effectiveness of the vaccine against Newcastle disease and increase in relative weight of liver and the levels of aspartate aminotransferase and lactic dehydrogenase enzymes. At 21 days, moderate hepatocellular hyperplasia was observed. In another study, contamination of 100 and 200 ppm FB1 in feed given to day-old turkey poults for a period of 21 days, resulted in decreased weight gain, heart and spleen weight, and increased liver, kidney and pancreas weight. There was significant gallbladder hyperplasia.
Dietary level of FB1 (75 ppm or higher) in turkey poults resulted in poor performance, increased organ weight, diarrhea, biliary hyperplasia, hepatocellular hyperplasia and rickets. Feed contaminated with graded levels of total fumonisins (33, 66, 99, 132, 231, 330, 429, 528 and 627 ppm) fed to one-day old turkey poults caused liver lesions at equal to or greater than 99 ppm, mild hepatocellular hyperplasia at 99 and 132 ppm, moderate to severe at 330 ppm and severe at 429 ppm and higher level of contamination. Turkey poults fed on FB1 contaminated feed for 21 days suffered mild hepatic lesions at 75 ppm, cardiac lesions at 475 ppm, decreased performance at 325 ppm and increased liver weights at 25 ppm.
In poultry, gross lesions of fumonisin toxicity include enlargement of liver, kidney, pancreas, proventriculus and gizzard, atrophy of lumphoid organs and rickets. Histopathologically, fumonisin toxicity caused multifocal necrosis of hepatocytes, hyperplasia of hepatocytes and bile ductules and hypertrophy of kupfeer cells. The intestine had villus atrophy and goblet cell hyperplasia, and myocardium and skeletal muscles had mild lesions with depletion of lymphoid tissues.
Safe levels of mycotoxins in feed: Aflatoxicosis, mostly caused by AFB1 and ochratoxicosis have produced severe health and economic losses in the poultry industry affecting ducklings, broilers, layers, turkeys and quail It is very difficult to indicate the safe level of mycotoxins in feeds. There are many factors that contribute to the difficulty of establishing levels of safety. However, the tolerance level of aflatoxins is 0.10, 0.15 and 0.05 ppm in broiler chickens, layers and turkeys. In 1986 the Codex Alimentarius Commission reported maximum tolerance limits for aflatoxin B1 in raw materials used for livestock feed by Denmark (50 ppb), Federal Republic of Germany (200 ppb), Italy (500 ppb), Netherlands (1000 ppb) and France (100 ppb). The European Economic Community (EEC) has proposed maximum aflatoxin tolerance level of 200 ppb in raw feed materials. The Food and Drug Administration (FDA) of USA has established the action level for aflatoxin at 100 ppb in feeds used for mature poultry. However, most of the countries have put the tolerance level of aflatoxin in complete feedstuffs for poultry at 20 to 50 ppb, whereas in India it has been fixed at 120 ppb for peanut meal (export). The LD50 values (mg/kg body weight) for AFB1 in ducklings are 0.03, in ducks 0.05 and in chicken 0.20. Acute toxicities can be observed in one-day-old ducklings with the LD50 of 0.36, 0.78, 1.70 and 2.45 for AFB1, AFB2, AFG1 and AFG2, respectively. The level of AFB1 producing liver lesions in poultry has been cited to be 50 ppb for chicken, 3 ppb for ducklings and 30 ppb for turkey poults. The LD50 for ochratoxin A in chicken has been found to be 3.3 mg/ kg body weight. Wyatt (1979) reported the toxicity of ochratoxin A in broilers, layers and turkeys fed with the levels of ochratoxin in feed ranging from 30 to 160 ppb.
Mycotoxin-mycotoxin interactions in poultry: Naturally contaminated feeds are more toxic than feeds with the same level of a pure mycotoxin supplemented into the diet, this is because of the presence of other unknown mycotoxins in the feed. When two or more than two mycotoxins are present in the feed, three types of interactions are possible: additive, synergism and antagonism. Additive interaction occurs when the combined effects of two mycotoxins are equal to the sum of the effect of individual mycotoxin. Synergism interaction occurs when the total effect of two mycotoxin is greater than the sum of the individual effect of each mycotoxin and antagonism interaction occurs when the combined effects of two mycotoxins are less than the sum of the effect of individual mycotoxin. This is a different and complicated subject, presenting great variability. Studies done up to date are scarce and do not allow to formulate definitive conclusions, even sometimes create confusion, because it is taken as a given that low concentrations of mycotoxins that individually would not produce any problems, should automatically induce problems when found combined in any given feed.
Sources of multi-mycotoxins contamination
- Single mould producing more than one mycotoxin on a single commodity
- Different moulds producing separate mycotoxins at the same time on a single commodity
- Different moulds producing separate mycotoxins on a single commodity
- Different sources of the same commodity each source contaminated with different mycotoxin used to prepare a feed
- Different commodities each contaminated with a separate mycotoxin used to prepare a feed
The following are published experiences of different cases of mycotoxin synergism and/or associations:
Synergistic effects of mycotoxins: Aflatoxin B1 (AFB1) and ochratoxin (OTA) are involved in most studies of synergistic interactions among mycotoxins in poultry. AFB1 as a hepatotoxin and OTA as a nephrotoxin were fed simultaneously to broiler chicks, and the toxicity was synergistic. Besides higher nephrotoxicity when these two mycotoxins were fed in combination, broiler livers contained markedly higher OTA concentrations upon combined administration with AFB1 than with OTA alone. Feeding diets containing both aflatoxins and OTA to chickens from hatching to three weeks of age resulted in significantly greater relative gizzard and kidney weights and less weight gain compared to either mycotoxin fed singly. AFB1 acts in synergism with T-2 toxin as well. Both mycotoxins affect protein synthesis, but by different mechanisms, which ultimately leads to synergistic effects. Bodyweight gain in 21-day-old broilers was reduced 16% from aflatoxin alone, 11% from diacetoxyscirpenol (DAS) alone and 36% from the combination of aflatoxin and DAS, indicating that they produce a significant synergistic interaction. Cyclopiazonic acid at 50 ppm interacted synergistically with aflatoxin at 3.5 ppm feed and adversely affected the growth of treated birds. The combination of OTA and cyclopiazonic acid significantly reduced the levels of serum total protein, albumin and cholesterol, whereas uric acid, triglycerides and creatine kinase activity were increased, resulting in an additive effect. Citrinin and penicillic acid were found to potentiate the nephrotoxic and carcinogenic effects of OTA, respectively. Fusaric acid was shown to be mildly toxic to embryos, and when a relatively nontoxic concentration of it was combined with graded doses of fumonisin B1 (FB1), it produced a synergistic toxic response. Total bodyweight gains, final bodyweights and feed conversion ratios of three-week-old broilers were significantly reduced by a deoxynivalenol (DON)/T-2 toxin combination but were not significantly affected by the toxins individually. The incidence and severity of oral lesions induced by T-2 toxin were increased in the DON/T-2 toxin combination, which indicates a synergistic effect. Chicks were given dietary concentrations of purified FB1 at 274 and 125 ppm and moniliformin at 154 and 27 ppm. FB1 and moniliformin, both alone and in combination, produced dose-responsive clinical signs and reduced weight gains and mortality in chicks, and additive effects were noted when the toxins were given in combination. The increased toxicity in poultry fed the combination of FB1 (300 ppm) and T-2 toxin (5 ppm) can best be described as additive, although some parameters not altered by FB1 or T-2 toxin singly were significantly affected by their combination. The additive effects-reduced bodyweight gain and feed intake and impaired immune function- of co-contamination of OTA and T-2 toxin in chickens have been observed.
DON+ AFB1: Day- old chicks were fed diets contaminated with 16 ppm of DON (individual contamination), 2.5 ppm of AFB1 (individual contamination) for 21 days. The following problems were observed: AFB1 decreased body weight gain and increased the relative weight of the spleen, liver and kidneys. Chickens suffered from hepatic hyperlipidermia and the levels of protein, albumin and phosphorus in the serum decreased, as well as the lactic dehydrogenase activity. DON decreased growth rate, increased feed conversion and increased gizzard relative weight. Also produced anemia, and decreased lactic dehydrogenase activity and triglycerides in the serum. AFB1+ DON combination caused the same problems previously cited. However, these symptoms were more severe. Yet, this increase in severity was not sufficiently significant to conclude that this combination of mycotoxins represented a synergic toxicity.
T-2 toxin+ AFB1: Day-old chicks given feed contaminated with 4 ppm of T-2 toxin (individual contamination), 2.5 ppm of AFB1 (individual contamination) and 4 ppm of T-2 toxin+ 2.5 ppm of AFB1 (combined contamination) for 21 days had the following consequences: T-2 toxin generated oral lesions, a decrease in protein, albumin, potassium and magnesium levels in the serum, as well as a decrease of certain enzyme activity in the serum. AFB1 resulted in a decrease in body weight gain and an alteration of protein, albumin, glucose, cholesterol, calcium, magnesium and enzymatic levels in the serum. Chicks also had an increase of relative liver, kidney, spleen, pancreas, proventriculus and heart weight. The combination of AFB1+ T-2 toxin had a serious impact on the severity of all previously mentioned conditions
T-2 toxin+ OTA: Day-old chicks given feed containing 4 ppm of T-2 toxin (individual contamination), 2 ppm OTA (individual contamination), 4 ppm T-2 toxin+ 2 ppm OTA (combined contamination) for 3 months, had the following responses:
OTA and OTA+ T-2 toxin decreased the nutritional efficiency of the feed. OTA individual contamination significantly increased the relative liver, kidney, gizzard and pancreas weight. OTA+ T-2 toxin increased the severity of previously mentioned effects and also decreased body weight gain, protein levels and lactic dehydrogenase activity in the serum. The interaction between these two mycotoxins resulted in an increase of triglycerides levels in the serum and a decrease in gamma-glutamic transferase activity and calcium in the serum.
T-2 toxin+ DON: Day- old chicks were given feed containing 4 ppm of T-2 toxin (individual contamination), 16 ppm of DON (individual contamination) for 21 days. The following problems were observed: T- 2 toxin+ DON contamination decreased body weight gain and body weight at the end of the test. However, these effects were not significant when individual contamination of T-2 toxin, and DON were given to chicks. Oral lesions were evident with T-2 toxin individual contamination, but these lesions were more severe with the combined contamination. Other parameters that remained unaffected with individual contamination, were significantly affected when both mycotoxins were present in combination.
DAS+OTA: Day-old chicks given feed containing 6 ppm of DAS (individual contamination), 2 ppm of OTA (individual contamination) and 6 ppm of DAS+ 2ppm of OTA (combined contamination) for 19 days, had the following adverse effects: All contamination decreased body weight. DAS and DAS+ OTA decreased the nutritional efficiency of the feed. There was a significant antagonistic interaction between OTA and DAS in uric acid and cholesterol. DAS+ OTA increased the relative liver, kidney and gizzard weight and decreased the total protein concentration and haemoglobin levels in the serum. Ninety percent of the chicks suffered oral lesions after consuming the different contaminants. OTA and OTA+ DAS resulted in severe nephropathy.
FB1+DON: Newborn chicks given feed containing 300 ppm of FB1 (individual contamination), 5 ppm of T-2 toxin (individual contamination), 15 ppm of DON (individual contamination), 300 ppm of FB1+ 5 ppm of T-2 toxin (combined contamination) for 19 to 21 days had the following problems: FB1 decreased body weight by 18 to 20%, T-2 toxin decreased body weight by 18%, DON reduced body weight by 2%, FB1+ T-2 toxin reduced body weight by 32% and FB1+ DON decreased body weight by 19%. Nutritional feed efficiency was especially affected by FB1, when present individually or in combination with other mycotoxins. There was 15% mortality in chicks fed with the combination of FB1+ T-2 toxin. Diets contaminated with FB1, with or without other mycotoxins, increased the relative weights of liver and kidneys and the levels of cholesterol in the serum. FB1 individual combination and combined contamination with T-2 toxin or DON increased the activity level of certain enzymes.
FB1+AFB1: Day-old turkey poults were fed diets contaminated with 75 ppm of FB1 (individual contamination) 0.2 ppm of AFB1 (individual contamination) and 75 ppm of FB1+ 0.2 ppm of AFB1 (combined contamination) for 21 days. Poults showed a decrease in body weight gain and significantly poorer feed efficiency when given AFB1 and AFB1+ FB1. The diet containing FB1 as an individual contaminant increased the relative weight of liver and spleen, while the diet containing AFB1+ FB1 in combination increased only the spleen weight. Feed containing AFB1 as an individual contaminant and feed combining both mycotoxins decreased albumin, total protein and cholesterol level in the serum. The sphinganine/ sphingosine relationship in the serum increased when poults were given feed containing FB1 as an individual contaminant and feed containing combined mycotoxins.
FB1+OTA: New-born Large White Nicholas female turkey poults given feed containing 300 ppm of FB1 (individual contamination), 4 ppm of DAS (individual contamination), 3 ppm of OTA (individual contamination), 300 ppm of FB1+ 4 ppm of DAS (combined contamination) and 300 ppm of FB1+ 3 ppm of OTA (combined contamination) for 21 days, presented the following problems: FB1 decreased body weight gain by 30 and 24%, DAS decreased body weight gain by 30%, OTA decreased body weight gain by 8%. FB1+ DAS decreased body weight gain by 46% and FB1+ OTA decreased body weight gain by 37%. Feed efficiency was negatively affected by all contaminated diets, except FB1 as an individual contaminant, which decreased body weight by 24%. All contaminations resulted in a significant increase of the relative liver weight, except feed containing DAS as an individual contaminant. Feed containing FB1 as an individual contaminant and as a combined contaminant (FB1+ DAS and FB1+ OTA) decreased cholesterol levels in the serum, increased certain enzyme activity, and altered some hematological values.
Control of mycotoxins: The best prevention starts in the fields were much of the basic ingredients such as cereal are harvested. It is in these fields were contamination begins. The interest in developing genetically modified cereals or varieties resistant to toxicogenic mold growth and proliferation, and insect attack is greater every day. However, the potential adverse effects on humans who consume these cereals have limited the studies on these prevention methods. These methods should be effective to work in facilities that are able to treat large quantities of food/feed or ingredients. Its application should be able to decontaminate, detoxify or inactive high concentrations of mycotoxins. These methods should take into account that mycotoxins can be protected inside the substrate, bound to protein structures or other components. Additionally, these methods must take in to account the fact that due to microflora zones, mycotoxins are not uniformly distributed throughout the ingredient. They must be efficient, affordable and should not significantly modify the nutritional value of the food/feed ingredient. The treatment should not leave residue which could later have adverse effects on the health of humans or animals. We will briefly mention several methods that can be applied, with some degree of efficacy, to prevent, decontaminate, detoxify and inactivate mycotoxin. Some of these methods are common in the food/ feed manufacturing industry.
The best way to prevent mycotoxin contamination in feed is to prevent the fungus growth in feed ingredients. Fungal growth may occur at pre-harvest stage i.e. in the field itself, at the time of harvest and at post-harvest drying and storage. The best prevention starts in the fields were much of the basic ingredients such as cereal are harvested. It is in these fields were contamination begins. The interest in developing genetically modified cereals or varieties resistant to toxicogenic mold growth and proliferation, and insect attack is greater every day. However, the potential adverse effects on humans who consume these cereals have limited the studies on these prevention methods. Good agricultural and good storage practices make the primary line of defense against mycotoxins contaminatiom of feeds. Therefore, we should establish a better understanding of the factors that are responsible for the mycotoxin contamination in the field, during harvest and in the storage. Mycotoxin problem is a difficult problem to manage in the poultry feed industry, but following methods are certainly useful in reducing the impact of mycotoxins in animal production.
- Crop rotation: Repeated monocultures of maize in the same field will enrich the soil with fungal spores, thus increasing the risk of contamination. Crop residues are the most important source of inoculums for Fusarium graminearum, which causes Gibberella ear rot and deoxynivalenol contamination of maize. Wheat and maize have been found to be particularly susceptible to Fusarium species and they should not be used in rotation with each other.
- Tillage: Removal, burning or burial of crop residues is likely to reduce Fusarium inoculums for the following crop.
- Plant breeding: Plant breeding can be considered as the best solution for Fusarium control in susceptible crops. Seed varieties that are resistant to seed infecting fungi and insect pests; and recommended for a particular region should be grown.
- Plant density: Avoid overcrowding by maintaining the recommended row and intra-plant spacing for the species/variety grown.
- Weed control: Weed can harbor fungi species and that is why a high weed density tends to increase infection in crops. Therefore, safe and suitable weed eradication practice should be adopted.
- Proper use of fungicides and insecticides: Insects reduce the external protection of grains and plant tissues thus, allowing the fungal hyphae to penetrate and have access to nutrients. Further, they also carry fungal spores. Adequate use of fungistats, fungicides and insecticides are recommended (caution should be exercised when using the last two, making sure that the residue levels are not harmful and within permitted parameters). These products not only residue the possibility of fungi growth and proliferation, but they also maintain the physical integrity of the grain (concerning insect attack). Insects not only attack and deteriorate the grain but also serve as transporting vectors that act as disseminators of microflora, contributing to fungi contamination. The grain intact integument protects fungi access in to the endospermic starch. However, the insects break the grains pericarp and the insect’s metabolism elevates the moisture in the grain allows the fungi to grow in the interior of the grain. The internal part of the grain is more vulnerable to fungi than the external part, cuticle, of the grain. Therefore, minimize insect damage and fungal infection in the vicinity of crop by proper use of registered insecticides, fungicides and other appropriate practices. The fungistats are often erroneously called “Fungicides”. Fungicides, however, destroy the cellular membrane of the fungi thus killing the fungi, as is the case of formaldehydes, pesticides, herbicides and others. Fungicides are not authorized to be use directly on food/ feed products, due to their toxic and pugnacious effects can cause serious consequences on animals and humans.
- Physiological stage of plants: Fusarium can produce more mycotoxins once a crop has ripened if harvest is delayed due to wet weather. Grain should be harvested as soon as possible once ripe.
- Keep birds away: Birds also contribute to the deterioration of the grain. This should be avoided using adequate method to scare them away from the fields, such as scarecrow.
- Harvesting: The equipment to be used for collecting and transporting the harvested grain should be clean, dry and free of visible fungal growth. During harvesting operation, avoid mechanical damage to the grain and avoid contact with soil.
- Drying: Immediately after harvest, determine the moisture content of the grains. Dry the grains to the desired moisture content recommended for safe storage of that crop.
- Cleaning: Cleaning and disinfection of all ingredients/feed circulating areas in the feed plant help reduce the growth of these toxicogenic moulds, as well as the possibility of mycotoxin production. The greater problem originate when the ingredients have been contaminated with mycotoxin before storage. Mycotoxins are present in highest concentration in damaged, broken and cracked grains. Screening and removal of these grains will help in reducing the mycotoxin concentration. These removed screenings should not be fed to poultry because of a potentially high concentration of mycotoxin in them. If there is visible fungal growth in the feed ingredients, the contaminated portion should be removed immediately. Thus, cleaning provides the first line of defense against mycotoxin contamination.
- Thermal treatment: Thermal treatments can also have good results. During food/feed manufacturing, the extrusion and expanded processes or even pelleting temperatures of 70-80°C are effective in reducing or eliminating the presence of fungi. However, mycotoxins are in general resistant to relatively high temperatures. Thermal detoxification effectiveness is limited to the amount of pressure used during these treatments, and the exposure time to certain temperature. Greater exposure can detoxify feed/food ingredients more effectively, but can also deteriorate them, making them not suitable for consumption. Furthermore, thermal treatments can be ineffective in treating some contaminations. Some mycotoxins such as aflatoxins, Ochratoxins A and fumonisins are resistant to temperatures of 120, 100, and 150°C, respectively. Patulin resists pasteurization and temperature of up to 100°C. Vomitoxin or deoxynivalenol resists temperatures exceeding 150°C, as well as those reached during the production of bread, cookies and other wheat products. T-2 toxin, Diacetoxyscirpenol and Zearalenone resists temperatures 120, 120 and 110°C, respectively. Toasting or frying peanuts, nuts, corn and other foods at 150-200°C for a period of 30 minutes can reduce AFB1 by 40-80%. A temperature of 120°C in autoclave for a period of 30-40 minutes can reduce AFB1 contamination in corn meal, peanut meal, rice, fruit and spices by 29- 95%. Autoclaves at 120°C for three hours can reduce the contamination of OTA in cereal based products by 70%.
- Quality control of feed and feed ingredients: One of the first steps to have in consideration for eliminating or reducing mycotoxicosis is the implementation of a rigorous quality control system for purchasing and utilization of raw material in the manufacturing of animal feed and food for humans. Other factors to be aware of are, constant hygiene and periodic disinfection of the storage of ingredients and of the food/feed manufacturing plants, and quality control analysis of finished products should be put in place in order to prevent mycotoxicosis risk.
- Cleaning of equipment: Feed handling equipment such as unclean feeders and unclean waterers may be a very good source of fungal infestation. Periodic cleaning of all feed handling equipment with a 5 to 10% bleach solution will help in controlling the mould growth.
- Holding time of feed: The manufactured feed is a very good source of nutrients for the animals as well as for the moulds. Therefore, it is very important to keep the time from the manufacture of feed to when it is consumed by the animal to as short as possible.
- Storage: Mould can grow and produce mycotoxins within a matter of days in a storage bin if grains are not dried and cooled thoroughly. The crop to be stored should be cooled as quickly as possible after harvest and dry the crop to a safe moisture level. Most of the spoilage problems during storage can be prevented by controlling grain moisture and temperature. Minimize the amount of foreign materials and damaged kernels in crop to be stored. The storage area should be dried and protected from rain and ground water. Protection from rodents and birds should be provided. Most of the mold spoilage problems during storage can be prevented by controlling grain moisture and temperature. Aeration in the stored grains also plays an important role. Fungi are aerobic organisms and thus, oxygen deficiency has a marked inhibitory effect on the formation of mycotoxin. Lower or nil concentrations of oxygen and higher carbon di oxide will result in the inhibition of aflatoxin production on stored grains. Moisture content in stored grains is an important measure for both mould growth and insect development. Moisture below 9% will inhibit the growth and development of rice and corn weevils. During the larval stage, an insect produces water and heat which is sufficient to start mould growth. In the feeds having moisture level of 12-15 percent, a combination of the mould and insect can lead to heating. A small increase in temperature in a Hot Spot will accelerate the insect metabolism and speed up the population growth. This will create an environment suitable for mould growth. Insect and mould utilize stored material as a food source for their own growth and reduce the nutritive value stored feed. The presence of insect and mould will give unpleasant odour and flavor to the feeds and reduce palatability and acceptability. The primary condition conducive to the growth of A. flavus, and therefore, the production of aflatoxin, is moisture. Hence, proper harvesting, drying, and storage will minimize mould growth and subsequent toxin production. All feedstuffs should be dried below the critical moisture content which permits the growth of moulds – approximately 12 percent. Additionally, mould inhibitors should be added to high moisture feeds that are exposed to air during storage.
- Use of fungistats or mould inhibitors: Fungistats have been used for years in animal feed and human food as inhibitors of the metabolism, growth and proliferation of fungi (mold and yeast). Fungi need to synthesize a series of enzymes in order to grow and proliferate. These enzymes are able to biodegrade the fungi substrate, and the degraded substrate becomes the source of nutrients for the fungi. Fungistats act as inhibitors of the synthesis of various enzymes at a cellular level, stopping fungi metabolism, growth and proliferation. Some fungistats modify intracellular pH, interfering with fungi metabolism, altering cell membrane permeability, making it difficult or inhibiting the transport of the bio-transformed substrate. These fungistats also inhibit the NADH (reduced form of nicotinamide adenine dinucleotide) oxidation, which is an important coenzyme in fungi metabolism. After using these fungistats, the risk of mycotoxin contamination will be reduced or eliminated. However, if mycotoxins are already present in the food, feed or ingredients, fungistats will have no effect on them.
Many chemical preservatives can also be used to prevent mould in stored grains. Organic acids such as propionic, acetic, butyric, fumaric, formic, sorbic and benzoic acids can be effectively used. Salts of organic acids for example, calcium propionate, sodium propionate and potassium sorbate can also be used. They have the advantage of being cost effective as well. Propionic acid is considered a safe compound for animal health. The level of organic acids in stored grain depends on the moisture level in the grains and on the type of acid. Recommendations for propionic acid application in maize vary from 0.1% for grains with 11-12% moisture to 0.5% for grains having 18% moisture content. Production of aflatoxin at 13% moisture level in poultry feed can be completely inhibited by adding propionic acid @ 0.25% or benzoic acid @ 0.30% or tartaric acid @ 0.40%. At 15% moisture level in feed, propionic and benzoic acid @ 0.5%, and tartaric acid more than 0.5% is required for complete inhibition of aflatoxin synthesis. However, at 17% moisture level in feed, more than 0.50% of propionic acid or benzoic acid or tartaric acid is required for complete inhibition of biosynthesis of aflatoxins. Propionic acid was more efficacious than benzoic or tartaric acid in inhibiting the synthesis of aflatoxins. Recommendations for fumaric and citric acid are 0.20 and 0.45%, respectively in poultry feed having 13% moisture.
There are certain things that should be kept in mind about mould inhibitors. Most of them do a good job of preventing mould contamination but do nothing for protecting the animal from mycotoxins that are already present in the feed. Mould inhibitors are not effective at controlling mould growth indefinitely; most of the mould inhibitors will lose their effectiveness after a short period of time.
18. Control enviromental factors that influence fungal growth:
a. Minimize moisture content of grain and feeds < 13%
b. Minimize relative humidity of grain and feeds < 70%
c. Minimize storage temperature of grain and feeds <20°C
d. Minimize oxygen availability during storage < 0.5%
19. Chemical treatment methods: Chemical detoxification methods consistently reduce aflatoxin concentrations. Some of these methods are: ammonia treatment, calcium hydroxide treatment and monomethylamine. These treatments can reduce aflatoxin concentrations by 98% in peanut meal, cotton seed meal and oil seed by transforming these aflatoxins in to non-toxic metabolites (aflatoxins B2a and G2a). Ammonia treatments decreased cysteine in ingredient by 15 to 30%; this treatment also caused discoloration of corn and the ammonia residue left an odd smell in the treated cereals. Calcium hydroxide and monomethylamine treatments did not reduce protein digestibility, net protein utilization, or interfere with the organoleptic characteristics of the primary ingredients. Boiling corn kernels in an aqueous solution of calcium hydroxide, followed by cooling and cleaning of the grains to remove the pericarp and excess calcium hydroxide can significantly reduce fumonisins contamination by converting these fumonisins to their hydrolysed form. Cleaned grains are used to manufacture corn products. However, the hydrolysed products could also be toxic.
20. Detoxification of mycotoxins: When all the above mentioned practices fail and the poultry farmer suspects that feed is contaminated with mycotoxins he can use the mycotoxin detoxifying agents. One way of reducing the mycotoxin exposure to animal is to decrease their bioavailability by including various mycotoxin adsorbing agents in the compound feed. These mycotoxin adsorbing agents are also called binding agents, adsorbents or binders. They should be able to bind the mycotoxins in contaminated feed without dissociating in the gastrointestinal tract of the animal. In this way the toxin-adsorbing agent complex passes through the animal and is excreted through faeces, thus, preventing or minimizing mycotoxin exposure of animal. Mycotoxin adsorbing agents such as HSCAS (Hydrated Sodium and Calcium Aluminosilicate), bentonites, montmorillonites, diatomaceous earth, etc. can be used for this purpose. Another way is the degradation of mycotoxins into non-toxic metabolites by the use of biotransforming agents. The use of enzymes that transform mycotoxins is also prevalent. These enzymes are incorporated in to the feed and biotransform mycotoxins in to derived compounds within the animal, which the animal later eliminates through urine and feces. In some cases, these animal derived compounds can be less toxic or not toxic at all, compared to the original mycotoxin. However, this is not so for some mycotoxins. Compounds as or toxic than the original mycotoxin can sometimes form during the intermediate reactions of the biotransformation.
HSCAS addition at 0.5 and 1% levels to 2.5 ppm AF contaminated feed moderately ameliorated the negative effects of AF on performance and biochemical parameters in quails. Inclusion of 0.5% HSCAS to AF (0.5 and 1 ppm) containing feed diminished the effects of AF on performance, relative organ weights, hematological and biochemical parameters associated with 0.5 ppm AF in turkeys. The addition of 0.5% HSCAS significantly recovered the growth inhibitory effects caused by 2.5 ppm AF. The increases in relative organ weights and the decreases in serum biochemical values caused by AF were significantly alleviated to differing degrees by HSCAS and HSCAS was found to be protective against the effects of AF in young growing broilers. Addition of HSCAS (Milbond-TX @ 1%) to AF (4 ppm) contaminated feed improved the performance, changes in organ weights, serum chemistry changes, and gross pathology observed in chicks fed AF. HSCAS also effectively reduced the incidence and severity of the hepatic and renal histopathology changes associated with aflatoxicosis. Incorporation of HSCAS and yeast cell wall component with two doses (0.1 and 0.2%) to AF (1 and 2 ppm) contaminated feed provided significant improvements by adding of HSCAS and less improvements by yeast cell wall components in performance, biochemistry and histopathology changes associated with aflatoxicosis.
Addition of 1% synthetic zeolite to 2.5 ppm aflatoxin contaminated feed significantly diminished the adverse effects of AF on performance and reduced the incidence and severity of hepatic histopathology lesions caused by aflatoxin in broiler chicken. Supplementation of 0.5% synthetic zeolite to 2.5 ppm AF containing feed resulted in significantly improved the adverse effects of AF on performance, hematology and biochemistry in broiler chicken. Inclusion of nanozeolite (0.25- 1%) into AF (500 ppb) contaminated feed significantly diminished the toxic effects of AF in performance and biochemistry in broiler chicken. Diatomaceous earth, sodium bentonite and zeolite at 0.5 or 1% level, alone or in combination, were partially efficacious in ameliorating the adverse effects of 300 ppb aflatoxin B1. Among these three binders tested, diatomaceous earth appeared to be the least efficacious in ameliorating aflatoxicosis in broiler chickens. Incorporation of sodium bentonite (@ 0.3%) to 2.5 ppm aflatoxin contaminated broiler diet provided significant improvements in liver histopatholgy and biochemistry. Supplementation of natural bentonite (0.3%) to aflatoxin contaminated (30-135 ppb) broiler diet reduced the severity of hepatic histopathology changes associated with aflatoxicosis. Sodium bentonite partially neutralized the effects of 3 ppm aflatoxin when included at 0.5% in the diet of broiler chickens. Supplementation of SB at 0.2, 0.4 and 0.6% levels to 2.5 ppm AF contaminated diet significantly ameliorated the deleterious effect of AF on humoral immunity. SB also improved the adverse effects of AF on performance and hematology and carry-over of AF from feed to eggs. In another study, addition of sodium bentonite at 0.3% level to 5 ppm aflatoxin contaminated broiler diet significantly improved the adverse effects of aflatoxin on performance, biochemistry and gross and histopathology of liver.
Supplementation of 2% clinoptilolite (CLI) to broiler diet containing 0.5 ppm aflatoxin ameliorated the toxic effect of AF and CLI provided significant improvement against AF toxicity in performance, biochemistry and liver histopathology. However, addition of CLI at 2% level to layer diet contaminated with 2.5 ppm AF provided no improvement in egg quality. Addition of CLI at 1.5 and 2.5% levels to broiler diet containing 2.5 ppm AF provided significant improvement in performance of broilers. Addition of 1.5% CLI also ameliorated the toxic effects of AF on hematology and biochemistry and reduced the number of affected broilers and the severity of gross and histopathological lesions caused by AF. CLI (1.5%) addition into broiler diet contaminated with lower levels of AF (50 and 100 ppb) significantly diminished the negative effect of AF on performance of broilers. Addition of 1.5% CLI also improved the changes in gross and histopathology of target organs and humoral immunity associated with aflatoxicosis.
Use of mannan oligosaccharides (MOS) and Saccharomyces cerevisiae (at the rate 0.05%, 0.1%, 0.2%) and their combination ameliorated the effect of aflatoxin partially or completely in dose dependent manner. The 0.2% level of MOS and SC is more effective than 0.05% and 0.1% level in counteracting the 300 ppb of aflatoxin in the feed. Inclusion of 0.1% MOS to 2 ppm AF containing feed significantly ameliorated the adverse effects of AF on performance of quail. Supplementation of mannanoligosaccharide (@ 0.11%) to 2.5 pmm AF contaminated feed decreased the gastrointestinal absorption of AF and its level in tissues in laying birds. Incorporation of 0.1% EGM to feed containing 2 ppm AF significantly ameliorated the toxic effects of AF on hematology and biochemistry. Addition of 0.1% EGM also reduced the number of affected broilers and the severity of lesions in the target organs caused by AF in broiler chicken. Inclusion of EGM at 0.05% and 0.1% levels to AF (60 and 120 ppb) contaminated diet resulted in significant improvements in performance, histopathology and leg deformity caused by AF. Addition of 0.05% EGM also removed the adverse effects of 100 ppb AF on serum biochemistry in ducklings. Supplemented of EGM at 0.05 and 0.1% levels to 100 ppb aflatoxin contaminated feed was effective in reduction of AFB1-induced hepatic injury in ducklings. Inclusion of esterified glucomannan (0.1%), SB (0.5%) and humic acid (0.2-1%) to 254 ppb AF contaminated broiler diet ameliorated the toxic effect of AF against humoral immunity. The addition of EGM, SB and humic acid to the AF contaminated diet ameliorated the negative effects of AF on ND antibody titers, but humic acid proved to be more efficacious in ameliorating the detrimental effect of AF on humoral immunity against ND.
Inclusion of 0.1% yeast cell wall into 250 and 500 ppb aflatoxin contaminated broiler diet was found to be effective in preventing the detrimental effects of AF on broiler performance. Incorporation of Saccharomyces cerevisiae extract (@ 0.5, 1, 2, 2.5%) in the quail diets containing 0.5 ppm aflatoxin suppressed the aflatoxicosis in quail tissues leading to improvement of growth performances and enhancement of expression levels of neural and gonadal genes. However, supplementation of 0.5% SCE and 0.75% natural zeolite to broiler diet contaminated with 1 ppm aflatoxin showed that addition of 0.75% zeolite did not reduce any of the adverse effects, whereas, supplementation of SC moderately ameliorated the effects in respect of performance and biochemistry. Addition of SCE at 0.2% level to 2 ppm aflatoxin contaminated quail diet significantly recovered the deleterious effects of AF on performance, egg production and egg weight. The addition of 0.2% SCE also provided significant improvements in hatchability and fertility of quails. In another study addition of SCE at 0.1% level to 2 ppm aflatoxin contaminated quail diet significantly reduced the effect of aflatoxin on performance. Addition of SCE at 0.1% level to 100 ppb aflatoxin contaminated quail diet partially ameliorated the ill effects of aflatoxin on performance of quails.
Supplementation of additional zinc at 40 ppm diet (total 80mg/kg diet) to the aflatoxin contaminated diet ameliorated the ill effects of 250 ppb aflatoxin on body weight gain, feed intake and feed conversion ratio, relative weight of liver, spleen and bursa, blood protein and uric acid, haemoglobin, SGPT, SGOT, H/L ratio and immune response of broiler chickens during 0-6 weeks of age. Addition of methionine 0.1% above the NRC recommendation in starting (total 0.6% Met) and finishing diet (total 0.48% Met) in the AF contaminated diet improved the production performance, relative weight of liver, spleen and bursa, blood biochemical and haematological parameters and immune response during 0-6 weeks age of broiler chickens experimentally induced with aflatoxicosis (250 ppb).
The protein level of the new or changed diet should be increased to 25 to 30%. Alternatively 1 to 2 kg methionine and 1.5 kg lysine hydrochloride may be supplemented per ton of feed with normal protein content. Supplementation of DLM at 500 ppm or methionine hydroxy analogue (MHA) at 769 ppm level in 500 ppb aflatoxin contaminated diet ameliorated the adverse effects of aflatoxicosis in Japanese quails. Both supplementation of DLM at 500 ppm and MHA at 769 ppm level in aflatoxin contaminated diet were equally efficacious in ameliorating the adverse effects of aflatoxicosis in growing Japanese quails. Fats and oil are beneficial in reducing aflatoxicosis and improving energy value of feed. Supplementation of selenium @ 2 to 3g, vegetable oil @ 10-20 kg with 300 g Choline chloride and 1 gram of vitamin E per tonne of feed is beneficial. Water-soluble vitamins and vitamin A should be added twice of the amount of required level. Supplementation of ascorbic acid @ 300 mg/kg diet is beneficial to counteract some of the adverse effects (viz. depressed egg production and electrolyte imbalances) of ochratoxin in laying hens under normal as well as elevated ambient temperature, at which ochratoxin is more toxic. Synthetic antioxidant like butylated hydroxy toluene (BHT) inclusion in the diet of broiler chickens at 1000 ppm level provided moderate protection against the adverse effects of aflatoxicosis in broiler chickens. Other toxin binders with varying efficacy are also available in market. Herbal mixture containing Acacia catechu 25%, Phylanthus niruri 40%, Andrographis paniculata 25% and base material 10% @ 0.5 to 0.75 kg per ton reduces the effect of aflatoxicosis. Inclusion of 0.5% montmorillonite clay into 4 ppm AF contaminated diet provided significant protection on growth performance, serum biochemistry, and the relative organ weight associated with aflatoxicosis in broilers. Supplementation of vitamin A (15.000 IU) to 100 ppb AF contaminated feed partially decreased the negative effects of AF on performance, biochemistry and pathology in quails. Addition of conjugated linoleic acid at 0.2 and 0.4% levels to AF (200 and 300 ppb) contaminated feed resulted in partial improvement in performance and biochemical parameters. CLA also diminished the detrimental effects of AF on liver pathology in broilers. Inclusion of 0.35% humic acid and 0.35% dried brewer yeast into AF containing feed (1 and 2 ppm) provided partial improvement in performance, hematology and biochemistry associated with AF toxicity in broiler chickens. Humic acid was found to be more efficacious than brewer yeast in ameliorating the adverse effects of aflatoxicosis in broiler chickens. Incorporation of Ca propionate at 0.25 and 0.5% levels to 100 ppb AF aflatoxin contaminated diet appeared to be effective in reducing toxicity of AF on performance and hepatic enzyme activities in broilers.
Esterified glucomannan (EGM) is effective in counteracting the adverse effects of mycotoxins, including T-2 toxin. Addition of 0.05% EGM to a naturally contaminated feed effectively alleviated the growth depression caused by the contaminated diet. Incorporation of EGM (0.1%) into aflatoxin contaminated (300 ppb) broiler diet significantly decreased the detrimental effects of AF on performance parameters, biochemistry and organ morphology. Addition of EGM (0.1%) and hydrated sodium calcium aluminosilicate (HSCAS @ 1%) to 2 ppm aflatoxin contaminated broiler diet and both adsorbents provided significant improvements in performance and relative organ weights associated with aflatoxicosis. Turmeric powder (0.5%) and HSCAS (0.5%) to 1 ppm aflatoxin contaminated broiler diet and the adsorbents demonstrated protective action in the deleterious effect of AF on performance, biochemistry, antioxidant functions and histopathology. Ammonia treatment to broiler diet contaminated with 1 ppm aflatoxin provided significant improvements in performance and hematology of broiler chickens. EGM prevented the Fusarium mycotoxin-induced alterations in haematology, serum chemistry and biliary IgA concentration. However, addition of 0.5% zeolite in the diet did not diminish the adverse effects of T-2 toxin and DAS on performance of broilers. The ill effects of 1ppm DAS on feed intake and body weight were counteracted by dietary supplementation of 0.75 or 1.5 g/kg of the Eubacterium-based product.
21. Processing of contaminated feeds for toxin inactivation: The physical and chemical treatments, found useful for inactivation of aflatoxins in contaminated feeds or ingredients includes:
- Raising the moisture levels up to 20% and autoclaving at 5 PSI for one hour followed by drying in an oven at 80°C with or without addition of sodium hydroxide (15 g per kg).
- Agitation of feed with Ca (OH)2 @ 2% followed by addition of formaldehyde at 15% moisture followed by autoclaving at 15 PSI for half an hour and drying.
- Ensiling after addition of liquor ammonia (6%, v/w) at 20% moisture for 20 days followed by drying at 35°C in an oven.
However, the feasibility of such processing methods has not reached to the farmers’ door. Moreover, such processing methods may not be suitable for poultry feeds. Therefore, the best way of using contaminated feeds are accurate estimation of contents for different mycotoxins for the determination of the safe incorporation of such feeds in compounded feeds.
22. Precautions to be taken at the farm
- Feed troughs should be periodically emptied, and disinfected with a 5% sodium hypochlorite solution. Continuous topping up of feed through is a bad practice. Feeder system should be turned off weekly so that the animals will be forced to clean out all the feed in the troughs before it becomes excessively old and moldy
- Animal houses need to have adequate ventilation. The air inside these houses can be very humid due to respiration and defecation. The whole house including its facilities should be thoroughly cleaned before placing new animals into the houses.
- Leftover old feed should not be brought back to the mill after removing the flock as old feed can be a source of contamination
- Do not use recycled bags if they are wet or exhibit signs of mouldiness.
- Reduce stress to animals
- Reduce intake of suspected contaminated feed by 50% or replace completely
- Dietary manipulations. Because mycotoxins typically reduce nutrient absorption, one approach to alleviate these effects has been to increase levels of critical dietary nutrients
23. General recommendations to reduce the effects of mycotoxicosis
The following are general recommendations that can attenuate the effects of a mycotoxicosis in animals once these effects have already started.
(a) Increase the level of protein and energy in the diet, as well as the levels of some vitamins, especially riboflavin and D3, given that these vitamins help animals, especially poultry, to detoxify mycotoxin such as AFB1. On the contrary, a deficiency in thiamin has a protecting effect against aflatoxicosis since its deficiency mobilize the lipid reserves, interfering with the hepatic metabolism of aflatoxins.
(b) Provide the contaminated feed to adult animal, except breeding animals. The susceptibility to mycotoxins decreases with age.
(c) Use low level of broad spectrum antibiotics with vitamins and electrolytes in drinking water.
(d) Increase the levels of methionine and cystine in the diet. These amino acids are the precursors of glutathione, which forms conjugated complex with AFB1 inside the animal and especially in the liver. These complexes are then eliminated through feces and urine.
(e) Maintain animals at relatively low temperature. Poultry are more susceptible to aflatoxicosis at high temperatures.
(f) Reduce or eliminate factors that could produce stress in the animals such as sudden changes in temperature and moisture, vaccination, lack of water, inadequate ventilation or high levels of ammonia.
(g) Reformulate the feed using a lower concentration of contaminated ingredients.
(h) If the contaminated ingredients (s) cannot eliminated, give the feed containing the ingredient (s) to animals that are less sensitive, or not sensitive to the mycotoxin that is contaminating the feed.
Mycotoxins can produce a significant reduction in the performance of poultry even at low concentration i.e., 0.02 ppm for aflatoxin and 0.1 ppm for ochratoxin. Poultry is found to be less susceptible to the estrogenic effects of ZEN. At large concentrations in feed, the ill effects of ZEN in poultry may include vent enlargement and secondary sex characteristics. Relatively high concentration of fumonisins are required to produce negative effects in birds as chicken, duck and turkey appear to be fairly resistant to the toxic effects of fumonisins. TCT may impair performance of poultry even the birds receive balanced diet, so care should be taken while selecting the feed ingredients, as TCT mycotoxins are considered as the most potent amongst Fusarium mycotoxins affecting poultry production. Many chemical preservatives can also be used to prevent mould in stored grains. Organic acids such as propionic, acetic, butyric, fumaric, formic, benzoic, tartaric and citric acids can be effectively used. Mycotoxin detoxifying agents such as zeolite, sodium bentonite, mannan oligosaccharides, Saccharomyces cerevisiae, methionine and zinc can be effectively used in combating deleterious effects of aflatoxicosis in poultry.
This article was originally published as a Technical Bulletin by Avian Nutrition & Feed Technology Division, CARI, Izatnagar-243 122 (UP).