Biointeraction of chelated and inorganic zinc with aflatoxin on carcass quality characteristics of broilers

Introduction

Mycotoxins are secondary metabolites of low molecular weights produced by certain strains of filamentous fungi such as Aspergillus, Fusarium and Penicillium, which invade crops in the field and may grow on foods during storage under favaourable conditions of temperature and humidity. The most common mycotoxins are aflatoxins, fumonisins, ochratoxin A, trichothecenes, zearalenone, and out of which aflatoxins (AF) commonly contaminate a wide variety of tropical and subtropical food/feedstuffs (Katole et al., 2013).

Aflatoxicosis is a common problem in poultry leading to severe economic loss in poultry farming. Supplementation of nutrients such as protein (Beura et al., 1993), vitamins (Johri et al., 1990) has been tried to counteract aflatoxicosis in broilers. In the recent study, it is reported that Zn in inorganic form was utilized by the fungi and subsequently increased AFB1 production and Zn in chelated form is unavailable to fungi for AF production in maize (Shamsudeen et al., 2013; 2014). However, investigations on supplementation of zinc (Zn) and their sources against aflatoxicosis are limited especially on carcass characteristics and hence a study was formulated to find out the effect of aflatoxin (AF) on carcass quality characteristics and the counteracting effect of supplemental Zn in chelated (organic) and inorganic form against aflatoxicosis in broilers.

Materials and Methods

The AF was produced from Aspergillus parasiticus NRRL 2999 (maintained in Mycotoxin Laboratory, Central Avian Research Institute, Izatnagar) in rice as per method of Shotwell et al. (1966) and in Yeast Extract Sucrose (YES) broth containing 15% sucrose and 2% yeast extract powder (Tsai et al., 1984). After incubation period, the cultured rice was autoclaved, dried and ground to fine powder, whereas the AF from YES broth was extracted using chloroform, condensed in thin film rotary evaporator, subsequently precipitated in hexane and then filtered as crude AF. The precipitated crude AF collected from liquid media was thoroughly mixed with 1 kg starch and it was added to 20 kg finely ground maize in batches and mixed properly. The AF content in representative sample of rice and maize powder was measured by preliminary extraction of AF (Pons et al., 1966) and subsequent analysis by thin layer chromatography (TLC) method.

Biointeraction of chelated and inorganic zinc with aflatoxin on carcass quality characteristics of broilers - Image 1

Day old broiler chicks were distributed randomly on uniform body weight basis into9 treatment groups with 3 replicates per group and each replicate- had 10 chicks. All the chicks were reared battery cages under uniform and standard management practices with ad libitum feeding and watering. All birds were immunized against Marek’s Disease and New Castle Disease at day old by occulo-nasal route and against Infectious Bursal Disease at 14th day of age. Two basal diets were formulated for starter and finisher phase of growth to meet the requirement of the entire essential nutrients for broiler. The experimental design followed was 3 × 3 factorial and the experiment consisted of 9 treatments as follows:

T1 – Basal diet
T2 – Basal + 0.5 ppm AF B₁
T3 – Basal + 1 ppm AF B₁
T4 – Basal diet + 200 ppm Zn from chelated source
T5 – Basal + 0.5 ppm AF B₁ + 200 ppm Zn from chelated source
T6 – Basal + 1 ppm AF B₁ + 200 ppm Zn from chelated source
T7 – Basal diet + 200 ppm Zn from inorganic source
T8 – Basal + 0.5 ppm AF B₁ + 200 ppm Zn from inorganic source
T9 – Basal + 1 ppm AF B₁ + 200 ppm Zn from inorganic source

Commercially available zinc sulphate and zinc propionate were used as source of inorganic and organic zinc respectively. At the end of 42nd day of age 6 birds per treatment were randomly selected and slaughtered for study of eviscerated yields, organ weights (gizzard, heart, intestine, liver) and cut-up parts’ yields (back, breast, drumsticks, neck, thighs and wings). The carcass traits were expressed as per cent of pre-slaughter live weight. The recorded data were statistically analyzed as per the method suggested by Snedecor and Cochran (1989). The means of different dietary treatments were tested for statistical significance using Duncan multiple range test (Duncan, 1955).

Results and Discussion

The result of the study is given in Table 1. The relative weight of heart did not differ significantly due to AF levels, but the different organ weights and cut-up parts yields differed significantly due to AF levels. The eviscerated yield was significantly (p<0.01) higher in basal AF level (practically undetectable level) followed by 0.5 ppm AF than 1 ppm AF level. The relative weights of giblet and liver significantly (p<0.01) increased in dose dependent fashions which were lowest in basal AF level and highest in 1 ppm AF level due to the effect of dietary AF levels. The relative weights of gizzard and intestine were significantly (p<0.05) lower in basal AF or 0.5 ppm AF group than 1 ppm AF group. The mean breast weight was significantly (p<0.05) higher in basal AF level than 0.5 ppm or 1 ppm AF levels. The back, drumstick and neck were significantly (p<0.05) higher in basal and 0.5 ppm AF levels than 1 ppm AF level.

Non-significant effect was observed on eviscerated yields, relative weights of giblet, gizzard and heart due to Zn supplementation. However relative weights of intestine and liver were significantly (p<0.01) higher in Zn unsupplemented group than organic or inorganic Zn group. The relative weights of back, breast, drumstick and neck did not differ significantly either due to different Zn supplementation. The eviscerated weights, cut-up parts’ yields and organ weights except liver weight did not differ significantly due to interaction between Zn supplementation and AF levels.

The relative weight of liver was significantly lower in all Zn groups at basal AF than any other groups. The liver weights of organic or inorganic Zn supplemented groups at 0.5 ppm AF were significantly lower than Zn unsupplemented group at 0.5 ppm AF, but were higher than AF unsupplemented groups. Similarly, the liver weights of chelated or inorganic Zn supplemented groups at 1 ppm AF were significantly lower than Zn unsupplemented group at 1 ppm AF, but were higher than AF unsupplemented groups.

The result of present study revealed that dietary AF at 0.5 and 1 ppm AF level decreased the eviscerated yields, which is similar as reported by Doerr et al. (1983). It also revealed that the relative weights of giblet and liver increased significantly due to dietary AF levels in a dose related fashion which is in agreement with earlier finding of Dafalla et al. (1987) and Kiran et al. (1998). The relative weights of gizzard and intestine increased significantly (p<0.05) in higher level of AF (1 ppm AF). The supplemental Zn either in chelated or inorganic forms partially reduced the weight of intestine and liver during aflatoxicosis, when compared to Zn unsupplemented group. Wyatt et al. (1985) also reported partial effect of Zn against aflatoxicosis in dairy calves. Maurice et al. (1983) found that the AF increased liver weight as well as decreased the hepatic Zn. The supplemental Zn might have increased the Zn status, which in turn increased the hepatic Zn and the increased hepatic Zn might have protected the liver from oxidative damage by AF. Similarly, the Zn might have protected the intestine from inflammation of intestine by AF. Hedemann et al. (2006) found that high dietary Zn increased the mucin staining area of large intestine in pigs and reported beneficial effect of Zn on intestinal physiology. The breast yield decreased significantly at 0.5 and 1 ppm level of AF, which is similar to the finding of Huff et al. (1984), where as the percentage of back, drumstick and neck decreased significantly at 1 ppm AF level. The supplemented Zn had no effect on these parameters.

Conclusion

Based on the results it is inferred that aflatoxin reduced the eviscerated yields and increased the relative weights of giblet, intestine and liver. It also affected the cut-up parts` yields mainly through reduced breast yield. The supplementation of zinc either as chelated (organic) or inorganic form reduced the weights of intestine and liver, while it had no significant effect on cut-up parts’ yields.

Acknowledgement

The authors are thankful to M/s. Kemin Nutritional Technologies (India) Pvt. Ltd., Gummidipundi, Chennai for supplying zinc propionate as a chelated (organic) to the team.

This article was originally published in Journal of Poultry Science and Technology, July-September 2014, Vol 2, Issue 3, Pages 48-51.

Biointeraction of chelated and inorganic zinc with aflatoxin on carcass quality characteristics of broilers

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