Effects of Phytase, Xylanase, Amylase and Protease Inclusion at Full Matrix Specifications in Diets for Broiler Chickens

This study aimed at determining the effects of phytase alone and in combination with XAP at full matrix specifications on growth performance, nutrient digestibility, carcass yield, toe ash, gastrointestinal organ weight and pH, energy utilisation (AME, AMEn, and ME:GE), and the digestibility of key nutrients in the jejunum and ileum of broilers fed complex diets. Day-old mixed-sex Cobb 500 broilers (n = 384) were assigned to four dietary treatments with eight replicates of 12 birds per treatment from d 0 to 42, with energy utilisation determination from d19 to 21 and digestibility determination at d21. The treatments were as follows: a positive control (treatment 1, PC) formulated meeting nutritional requirements and three test diets reformulated with reduced nutrients and energy according to respective matrix values of the enzymes used. The enzymes supplemented are: treatment 2, a mixed enzyme (NC1 + XAP, 100 g/ton with activities of 2000 U/kg xylanase, 200 U amylase and 4000 U protease, respectively); treatment 3, a novel consensus bacterial 6-phytase variant (NC2 + PhyG) at 1000 FTU/kg; and treatment 4 (NC3 + XAP + PhyG, PhyG at 1000 FTU/kg and XAP combination). Overall, enzyme inclusion with full matrix application maintained overall weight gain, feed intake and the FCR. There were significant increases in starch, Ca, P and Na digestibility with almost all enzyme inclusions (p < 0.05). NC2 + PhyG and NC3 + XAP + PhyG reduced the feed cost/kg live gain compared to PC (p = 0.006). In conclusion, this study demonstrates that the full matrix values for phytase alone or in combination with XAP may lower the cost/kg live gain while maintaining the growth performance of broilers offered a complex diet with increased use of locally available ingredients (rapeseed and lupins).