The gut health of poultry is important not only because of its effects on productivity, but also because impaired gut integrity can increase susceptibility to enteric pathogen invasion.
Osmotic stress and heat stress can both damage the lining of the gut. Finely ground and pelleted diets of high digestibility exert considerable osmotic stress on gut lining, which may exceed the cell's ability to maintain water homeostasis and ionic balance.
Many studies have shown that the ability of the gut to withstand osmotic stress can be improved by supplementation with betaine, an organic osmolyte, and that this results in decreased susceptibility to enteric pathogens. During heat stress, blood is diverted to the periphery at the expense of the gut, the integrity of which can be compromised by reactive oxygen species generated by an insufficient supply of nutrients and oxygen.
If heat stress is sustained, the ability of the glutathione cycle to prevent reactive oxygen species from destroying cell membranes may be overwhelmed. Supplementation with selenium yeast has been shown to increase activity of the glutathione cycle in heat stressed poultry, which may prevent heat-induced damage to gut lining.
The gut health of livestock species has received scant attention in the past, largely because the threat of pathogens that might have entered the body through an impaired gut lining was negated by the routine use of antibiotic growth promoters.
The fact that poultry industries in countries where antibiotic growth promoters have been banned are now experiencing an increase in health problems and infections associated with enteric pathogens indicates that the gut health of poultry reared in modern production systems is far from optimal.
Impaired gut health is economically significant for the industry not only because it affects the productivity of birds, but also because human outbreaks of food borne illnesses associated with poultry products affect the market for poultry products.
Although pathogenic organisms are always present in the gut, beneficial gut bacteria and the host's gut immune system normally restrict the numbers of pathogens present. High numbers of gut pathogens result when these defence mechanisms are impaired. This article discusses how osmotic stress and heat stress can impair gut integrity of poultry, and describes corresponding protective measures.
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Article made possible through the contribution of Australian Poultry Science Symposium (APSS) 2007.