Production of broilers with high growth rate and feed efficiency through impressive genetic improvement is often directly linked with digestive problems, such as passage of undigested feed (or) feed passage syndrome with impaired gut health function. The passage of undigested feed inside the poultry house is a sporadic problem in integration or individual farms mainly during rainy season. This may be due to the limited availability of major raw materials in diet and poor management practices. The incidence was close to that observed during 1996 due to poor grain harvesting after consecutive years, but the severity is much lower at present. According to the statistical analysis, the loss of feed at one chicken was around 0.08USD due to feed passage, apart from the cost of medicine.
Many factors should be considered to influence the rate of feed passage through the digestive tract in birds, e.g. nutrient interaction time with digestive enzymes, absorptive surfaces and microbial populations. The main observation as shown in Figure-1 is the presence of large corn particles, excess moisture, a characteristic green coloration with orange mucus and poor formation to the feces. Affected broilers had poor pigmentation, deprived feed conversion, lower bodyweight and variable flock uniformity. The lesions are primarily observed on the proventriculus, gizzard and small intestine.
Major challenges for poultry farmers and veterinarians are the passage of undigested feed or wet droppings which are the typical finding related to a wide scope of potential causes. But many times, broiler farmers tends to point out the quality of feed. However, lack of consistency of the issues in farm indicates that the additional factors can also be addressed. Therefore, this editorial mainly deals with the summary of causes and preventive measures that should be considered when passage of undigested feed is noted in broilers.
FACTORS RESPONSIBLE FOR FEED PASSAGE
Normal function of intestinal tract mainly depends on the presence of large bacterial population and any imbalance in this flora is mainly responsible for disease. Utmost important cause after viral or parasitic infection is the necrotic enteritis, which may be due to secondary bacterial infection or dysbacteriosis caused by C. perfringens. Overgrowth of C. perfringens occurs due to coccidiosis, which damages the gut lining and reduces the intestinal passage of ingesta. Younger broilers with clinical and subclinical coccidiosis usually associated with the species, E. acervulina and E. maxima can cause passage of undigested nutrients in the feces. Similarly, mild infestation of ascarides and cestodes cause gut irritation and feed passage. Some common factors responsible for feed passage in broilers are detailed in Figure-2.
Poor grain quality with mold growth is a primary contaminant source for mycotoxins, which affect the functioning of digestive system and hinders proper digestion of feed. Common examples are: ochratoxins increase intestinal fragility, aflatoxins decrease bile secretion due to blockage of bile ducts and trichothecenes causes erosions to oral cavity, proventriculus, gizzard and intestine. Both the quality of feed and drinking water should be prime suspects whenever feed passage becomes prevalent. Poor quality water with high level of total dissolved solids (TDS), minerals and pH causes irritation in the gut and inefficient nutrient absorption leading to rapid feed passage. Anti-nutritional factors like gizzerozine, biogenic amines, tannins, trypsin inhibitors and rancid fat further worsen the process of feed grinding by causing gizzard erosions, sloughing of intestinal epithelia, enteritis, etc. Some authors claimed that trypsin inhibitors present in soybean meal (SBM) was directly linked to feed passage outbreaks. Similarly, feed ingredients like wheat, barley, rye or cassava (tapioca or yucca) often cause excess wet droppings due to high content of soluble non-starch polysaccharides (NSP’s). The digesta produced by high levels of NSP’s makes favorable conditions for potentially harmful bacteria, such as C. perfringens.
Faulty management practices of acidification, disinfection, sanitization, litter, ammonia, etc. can increase intestinal bacteria proliferation and make animals more prone to dysbiosis. Sometimes, the level of excess salt intake can result from mixing errors in the feed by not considering the level in fishmeal and drinking water responsible for voiding excess water through the feces with undigested feed. Litter is the first material that recently placed young chicks may consume, before finding feed and water. Ingestion of contaminated litter can cause irritation of the gut linings of young chick, resulting in poor nutrient absorption. Equally, environmental stress conditions should not be ignored as a potential cause of wet and poorly formed feces. High temperature and humidity in the broiler house will increase water consumption and the moisture content of droppings.
As referred earlier, the fundamental circumstances wherein feed passage happens is either when there is disintegration on the tissues of gut that impede its working or when there is intestinal microbiota imbalance. It is therefore critical to recognize the reasons rapidly and to make suitable strides before a substantial issue creates. When remedial measures are set up, birds normally recover equally fast. The regular use of functional additives (organic acids, exogenous enzymes and prebiotics) play a crucial role in keeping up great well-being and decreasing the assimilation of pathogenic microorganisms of the digestive tract of birds. It is well known that protected butyric acid is an excellent growth promoter as it enhances performance, regulates gut health issues caused by bacterial pathogens, promotes the regeneration of necrotic areas and facilitate tissue development and repair. Close monitoring of the effectiveness of anticoccidial management program is another step to consider. In the event that the sub-clinical issue continues at farm level, any current anticoccidial program should be re-evaluated to improve disease management, may be by changing the turn of anticoccidials in feed or implementing appropriate vaccination. Some strategies that need to be followed to prevent feed passage in broilers are shown in Figure-3.
Quality of feed ingredients should be improved by focusing on the consistency of grains, soya and fat quality; addition of enzyme preparations to avoid undigested feed to be the substrate for pathogenic microorganisms. Modification of the diet and addition of exogenous enzymes to wheat, barley, oat or rye-based diets can considerably decrease NSP level and reduce the risk of necrotic enteritis in flocks fed with these cereals. Minimizing the level of fishmeal, wheat, barley or rye in the diet can help prevent this condition. Apart from this, such type of issues can be avoided by desirable feed quality along with everyday cleaning and disinfection of feeding equipments; removal of any caked and moldy residues lodged within the system.
It is essential to avoid development of mold in feed by feeding quality grains and storing the feed under appropriate conditions. Mold inhibitors and binding agents should be included in grains to decrease the negative impacts of mold development and mycotoxins individually. Incurable or diseased birds should be removed promptly, as they can serve as a source of toxicosis or infection due to cannibalism. To govern the problem of drinking water, disinfection or acidification remedy can be validated. Management practices should be streamlined by paying attention on litter quality, farm hygiene, field of feeding, temperature and humidity of the house. It is necessary to make sure that the litter is of top quality, free from foreign materials and fresh.
Factors associated with feed passage in broilers can negatively affect the gut health status and production performance of birds. The most efficient manner to resolve the problem is to evaluate the basic management practices that play a vital role in preventing this problem. Feed passage directly affects the broiler economic performances like feed conversion and body weight. Therefore, a standardized scoring technique can be used to evaluate the sub-clinical issues related to intestinal health in general to make the modification of strategies accordingly. Feed passage in poultry will keep on being an infrequent issue in poultry integrations. It is essential to keep a receptive outlook, as there could be several causes and a little deductive reasoning may be needed to arrive at a diagnosis.