A number of diseases and conditions of the gastrointestinal tract (GIT) of monogastric animals are associated with the diet that is fed. Increasing evidence suggests that dietary nutrients/components can ameliorate and in some cases, prevent, some diseases and conditions of the GIT. Such a concept has become increasingly important in the intensive livestock industries, e.g., pigs and chickens, where there is increased legislative and consumer scrutiny and in some cases, bans and restrictions, on the use of some antimicrobial compounds used in these production systems. The European Union introduced a ban on the use of sub-therapeutic antibiotics in 2006, which created numerous challenges for these industries in terms of production, health and animal welfare. The predominant reason for this ban, and indeed the pervading reason for legislation and changes in other parts of the world subsequently, is increased resistance by some bacterial pathogens to antimicrobial compounds such as antibiotics and heavy metals (Zn, Cu), which have traditionally been included in feed and (or) water to reduce the prevalence of GIT pathogens.
It is beyond the scope of this paper to discuss the impacts of diet/dietary components on every disease and condition recognised in the GIT of these animals. Nevertheless, there are a number of economically significant diseases and conditions of pigs and chickens whose aetiology is embedded with a strong dietary influence. In pigs, diseases and conditions such as swine dysentery (SD), post-weaning diarrhoea (PWD), gastric ulcers and Salmonellosis are known to be affected by specific dietary nutrients and (or) components, or by the method of feed processing before being offered to the animals. Similarly and in chickens (both meat and egg birds), diseases and conditions such as necrotic enteritis (NE), wet litter, Salmonellosis, avian intestinal spirochaetosis, and Campylobacteriosis have a strong dietary influence. In companion animals, the nature of the diet(s) fed can have profound influences on laminitis in horses and small intestinal bacterial overgrowth in dogs, for example.
Research conducted by our group, amongst others, has shown that some of these diseases and conditions can be controlled and (or) prevented using specific nutritional manipulation, sometimes in the absence of antimicrobial compounds. For example, the use of lower protein diets and manipulation of type and content of the dietary fibre can impact upon the incidence of PWD and SD, whilst in meat chickens, the use of certain grains and carbohydrate fractions is known to influence NE. The influence of the diet on fermentation characteristics in the large intestine can also have associations with stool form and osmotic diarrhea. In this regard, positive aspects of some fermentative substrates (e.g., resistant starch, oligosaccharides, soluble fibre) for human nutrition often have negative consequences for monogastric animals from a production, faecal form, and (or) disease perspective.
Interactions between nutrients, components and (or) ingredients and the GIT to affect a range of diseases and conditions are complex. In a rapidly changing regulatory and consumer landscape, the monogastric production and companion animal industries face new challenges related to production, animal health and welfare.
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