Impact of Dietary Exogenous Enzyme Supplementation on Endogenous Secretion, Gastrointestinal Health, Nutrients Digestibility and Growth Performance of Poultry

Anti-nutritional factors in feed ingredients (ANF) can reduce nutrient utilization and suppresses gut health. Birds typically activate their innate immune system for protection against the adverse effects of ANF, which often involves the secretion of mucin. Although dietary supplementation of exogenous enzymes are commonly used to alleviate the adverse effects of ANF on apparent nutrient digestibility, little is known about how they affect gut health, particularly in relation to enteric mucosa morphological development, and the endogenous nutrient losses due to mucin secretion. The hypothesis of this dissertation centers on the impact of dietary enzyme supplementation on gut mucosa morphology and mucin secretion, in relation to digestibility and nutrient utilization. The primary hypothesis is: dietary enzymes reduce the ANF-inducing effects on enteric mucin secretion, which reduces endogenous nutrient loss and improves apparent nutrient retention and utilization towards growth efficiency. We carried out five studies to examine the hypotheses in turkeys and broilers, using different types of dietary ANF challenges and remedies of exogenous enzymes.;In the first 3 studies, we tested our hypothesis by challenging the birds with dietary non-starch polysaccharides (NSP), and evaluating the response to dietary supplementation of carbohydrases. In the first 2 studies, the NSP challenge was imposed by increasing dietary inclusion levels of DDGS in corn-soybean meal (SBM) diets, supplemented with a blend of endo-xylanase, alpha-amylase and protease (XAP), and direct fed microbial (DFM). Based on the outcomes of these first 2 experiments, we conducted the third study using the dietary beta-mannanase inclusion to resolve the beta-mannans ANF effects in high and low energy corn-SBM diets. The fourth and fifth experiment was conducted to further validate that our hypothesis that enteric mucin secretion is also relevant to explain the adverse effect of dietary phytate and the corrective response to phytase supplementation. The objective was to assess the effect of dietary inclusion of phytate, calcium and phytase up to 2000 FTU/kg on intestinal mucin secretion, nutrient digestibility, and growth performance of turkey poults.;The first two experiments revealed that the nutritional value of DDGS in corn-SBM diets for turkeys was not be improved by the XAP and DFM. The growth performance decreased as the DDGS inclusion levels increased. High dietary inclusion of DDGS also impaired jejunum villi development. Although supplementation of XAP and a combination of XAP+DFM had no effect on the BW, XAP improved apparent nutrient digestibility, and reduced intestinal mucin secretion. The results from third experiment showed that increasing dietary energy improved the growth performance, whereas the beta-mannanase addition did not have any significant effect of on the growth performance. However, beta-mannanase supplementation improved the jejunum villi development, crude protein, fat digestibility, apparent nitrogen retention (ANR), and lowered the ileal mucin secretion, presumably by reducing the endogenous loss of nutrients. In experiment 4 and 5, phytase supplementation significantly reduced the ileal mucin secretion, and improved nutrient digestibility and FCR. Both phytate and calcium enhanced the ileal mucin secretion. Although, the calcium level did not affect the apparent nitrogen retention (ANR), increasing dietary phytate level reduced the ANR, while the addition of phytase enzyme increased the ANR.;In conclusion ANF, such as NSPs and phytate, impairs the apparent nutrient digestibility and growth performance by suppressing enteric mucosa morphological development, and increasing endogenous loss of nutrients via enteric mucin secretion. In contrast, dietary supplementation of exogenous enzymes helps alleviate the adverse effects of ANF on nutrient utilization by directly or indirectly removing the mucosal irritation that stimulates enteric mucin secretion. Excess dietary calcium also enhances enteric mucin secretion as a compensatory response to the formation of insoluble viscous mucoid complexes, which further increases endogenous loss of nutrients and adversely affects apparent nutrient digestibility.