The efficacy of exogenous phytase and protease, alone and in combination, or in combination with AGP, zinc bacitracin on performance and intestinal morphology in broilers was tested. Broilers were fed a diet containing nutrients at recommended levels (positive control, PC) with no enzyme supplementation or a diet with lower nutrient density than PC, either without enzyme supplementation (negative control, NC) or with enzyme(s) (Treatments, Trt). Nutrient specifications of NC1, 2 and 3 diets were decreased by levels expected to be made available by Ronozyme® HiPhos, Ronozyme® ProAct and a combination of Ronozyme® HiPhos and ProAct, respectively. The NC1, 2 and 3 diets contained the same level of nutrients than the NC counterpart, but with the respective enzymes supplemented to the diets. At 34d of age, body weight (BW), but not feed intake (FI), of NC1 was lower (P<0.05), and feed conversion ratio (FCR) not significantly different than PC. With the addition of 100 mg/kg of a phytase product (Trt1), no difference in performance of broilers was noted compared to PC. Broilers in NC2 and Trt2 groups did not differ in performance from PC, suggesting that nutrients in NC2 were not lowered sufficiently to limit performance. BW and FI, of NC3 was lower and FCR was not significantly different than PC. With the addition of phytase and protease (Trt3), performance of broilers was similar to PC. Addition of zinc bacitracin to Trt3 did not improve any of the performance parameters compared to Trt3. There was no difference in metatarsal bone ash mass, ash concentrations, densities and percentage Ca and P of birds fed PC or NC or diets supplemented with enzymes. While no differences were found for the ileum, phytase supplementation to the diet increased the duodenal villi length: crypt depth from 8.20 (PC) to 10.75 and 10.79 (Trt1 and Trt3, respectively). No differences in this ratio were noted between PC and the NC diets. The addition of phytase, alone and in combination with a protease, increased the available nutrient levels, improved duodenal villi height to crypt depth ratio and subsequently improved broiler production. The study was therefore conducted to determine the efficacy of exogenous phytase and protease, alone and in combination, or in combination with AGP, zinc bacitracin on performance and intestinal morphology in broilers from day old to 35 days of age.
Dissertation (MSc (Agric))--University of Pretoria, 2017.