Beta-mannanase and Alpha-galactosidase supplementation of broiler chicken diets containing different levels of extracted coconut residue

Four studies were conducted to asses the efficacy of an enzyme preparation in its ability to hydrolyze pure target substrates and diets, and evaluate the effect on the growth and physiological responses of broiler chicken. In study 1, the kinetics of p-nitrophenyl alpha-D-galactopyranoside hydrolysis by alpha-galactosidase and locust bean gum by Beta-mannanase yielded a Vsub max of 102.04 u/mL and a Ksub m of 8.96 mM., and a Vsub max of 175.93 u/mL and a Ksub m value of 3.55 mg/mL at 40 deg C at pH 6, respectively. The optimum temperature and pH range of both enzymes were at 60 to 70 deg C and pH 6 to 7, respectively and were completely stable at 70 deg C at pH 6 for 90 mins preincubation. In study 2, three experimental diets containing different levels (0,2,4%) of extracted coconut residue (ECR) diets were incubated with enzyme using the two-stage in vitro digestion assay. Assayed diets with optimized enzyme concentration had significantly higher activity than diets with commercial inclusion rate and significantly reduced the viscosity of the feed extract. In study 3, six experimental diets containing different levels (0,2,4%) in started diets and (0,3,5%) in finisher diets without and with enzyme at commercial inclusion rate were fed to 360 broiler chickens. The viscosity of intestinal digesta was significantly reduced by addition of enzyme and highly correlated with in vitro viscosity of assayed diets (r=0.95047 ; p0.01). Increased level of ECR at 4% significantly impaired the weight gain, feed intake, feed efficiency, crude fiber digestibility, apparent metabolizable energy (AME) of ileal digesta and excreta, and increased the transit time and rate of feed passage. However, addition of enzyme reverse the negative impact caused by copra galactomannan. There was significant improvement on the weight gain, feed intake, feed efficiency, crude fiber digestibility, AME of ileal digesta and excreta, and decreased the transit time and rate of feed passage as reflected by the 14% increase in income over feed and chick cost. In study 4, diets with the highest level of ECR significantly increased the relative weight of proventriculus, gizzard, full and empty weight of small intestine, length of duodenum, jejunum and ileum. The mucosal development of jejunum of the birds fed with basal diet was documented at day 7 and 28, respectively. The Crypt depth, villous height, villous basal apicat width was increased by threefold and villous surface area was increased by eightfold. The mucosal morphometry of jejunum of birds fed basal diet containing 4% ECR without and with enzyme supplementation were documented. High level of ECR did not significantly affect the crypt depth and villous height of jejunal mucosa, however, significanly increased the villous surface area. Addition of enzyme significantly decreased the crypt depth, villous height and villous apical width while the basal width of the villous and villous surface area did not significantly differ from the control.