Threats to gut health in production animals

Abstract Text:

Demand for meat protein is steadily increasing due to an expanding population and increasing wealth in populous nations.  With finite supplies of arable land under increasing pressure, productivity gains through increased efficiency of animal production are essential for future food security.  However, regulations and public opinion have restricted the use of hormone supplements and antibiotics for growth enhancement.  There is thus a focus on other non-nutrient additives, including phytonutrients.  The gastrointestinal mucosa is a major determinant of feed conversion efficiency as it represents the first line of defence against enteric pathogens and is susceptible to disruption by events such as weaning, environmental (notably heat) stress, and infection.  Heat stress is increasing with global warning and a shift of agricultural production into tropical regions; in feedlot cattle and in intensive pig faming it can cause decreases in feed intake and growth, and in extreme cases may result in death.  The gut leakiness of heat exposure is associated with oxidative stress in the intestine, that is manifested by compromised glutathione peroxidase activity and increased levels of oxidised glutathione.  A further threat to gut health is rapid and early weaning.  Rapid weaning is required to maintain breeding productivity and effective herd management.  However, it is causes stress that is not associated with gradual weaning which occurs for animals in the wild.  The weaning transition in farmed pigs is accompanied by adverse changes in intestinal morphology, including villus atrophy, increased crypt depth, reduced absorptive capacity and reduced brush border enzyme activity.  The weaned animals lose weight, some animals die and those that lose significant weight lag behind their litter mates in weight gain.  In pigs, first litters show greater post-weaning deficits.  The third major threat, which is exacerbated by heat or post-weaning stress, and by intensification of production, is reduced resistance to enteric pathogens.  Intestinal bacterial infections can reduce average growth rates by as much as 40%.  The major hormone that promotes mucosal growth and repair is glucagon-like peptide 2 (GLP-2), which is released from L-type enteroendocrine cells.  These cells bear receptors that are potential targets for food additives.   In addition, number of phytonutrients and other food additives have anti-oxidant or mucosal protective qualities, for example cinnamaldehyde and selenium.  There is need to further advance understanding of mucosal biology and the actions of non-nutrient additives in production animals to improve gut health, animal health and productivity. 

Keywords: Gut health, mucosal integrity, heat stress, weaning, enteritis