F percent of production losses in broilers was due to direct effects of coccidiosis on mortality, weight gain and feed conversion and 18 percent due to the costs of prophylaxis and therapy. Nowadays, global annual financial losses due to coccidiosis are estimated to be 300 million USD. Hafez (2011) reviewed the prevalence of enteric diseases of poultry, with special focus on Clostridium perfringens. He indicated that its prevalence was drastically increased after the EU ban on AGPs, resulting in reduced animal performance, increased mortality rates and increased medication costs. Skinner et al. (2010) estimated that subclinical necrotic enteritis results in a loss to producers ranging from 450 – 750 USD per 10,000 birds. It is clear that a good understanding of these intestinal disorders is needed to be able to develop effective nutritional intervention strategies and feed additives to reduce intestinal disorders in poultry or alleviate its consequences.
The impact of nutrition on intestinal health
As indicated before, intestinal health issues can have different causes that need to be understood. Intestinal problems that have a nutritional base can be prevented by using well-balanced diets with good quality raw materials, although these are not always readily available. Correct estimates of the nutritional value of feedstuffs and a focus on e.g. reduction of fermentable substrates, proper thermal processing of feedstuffs to eliminate anti-nutritional factors and control for mycotoxins are crucial to minimise intestinal health challenges. It is well-accepted that using too high dietary crude protein levels can increase growth of proteolytic bacteria like Clostridium perfringens. Recently, Veldkamp at al. (2016) have shown that
Table 2. Effects of some feed additives on intestinal health in poultry (Dhama et al. 2014) Feed additive Probiotic
Effect Inhibits growth of disease causing organisms Prevents digestive upsets and diarrhoea caused by bacteria Creates balance in gut microbial population
Prebiotic
Positive effects on host by stimulating growth and activity of beneficial bacteria
Organic acids
Ability to reduce pathogenic and spoilage organisms by lowering gut pH
Antimicrobial peptides
Components of the innate immune system and possess antibacterial and immune-modulatory properties Kill a broad range of microbes including bacteria, fungi and viruses Reduce anti-nutritional factors and degrade nonstarch polysaccharides Degrade phytate and increase availability of minerals Bind and immobilisation of toxic material (mycotoxins) in the GI tract Improve nutrient digestibility, especially crude protein with focus on intestinal health Reduce oxidative stress & fatty acids oxidation and improve barrier functions in the GI tract Exert antibacterial effects at high dosages Inhibit quorum sensing and reduce toxin production at low dosages
Exogenous enzymes
Clay minerals Phytogenics
reducing dietary electrolyte balance (dEB) significantly reduced wet litter incidence in turkeys and subsequently improved paw quality. In their study, soybean meal was exchanged by vegetable protein sources with lower potassium contents to reduce dEB. This approach however, can result in an increase in feed costs. Fermentable substrates can also be reduced by the use of
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