Phytase in Broiler Rations- Effects on Carcass Yields and Incidence of Tribal Dyschondroplasia

Two broiler trials were conducted to marketing ages of 7 and 9 weeks, for Trials 1 and 2, respectively. In Trial 1, three diets were administered: 1) NRC non-phytate phosphorus (NPP) (0.45%), 2) low NPP (0.30%), and 3) low NPP (0.30%) plus 500 units Natuphos® [1] phytase/kg ration. Each of the diets was fed to female Ross × Ross chicks for 7 weeks. Low NPP rations had a negative effect on body weight at 7 weeks of age, which was overcome by phytase supplementation. Feed conversion ratio was not affected by NPP level or phytase. Overall carcass yields were not affected by NPP level; however, leg quarter weights were significantly greater in broilers fed the low NPP plus phytase diet. The second trial was a 3 × 2 factorial arrangement of three NPP levels (NRC recommended, 75% of NRC recommended, and 50% of NRC recommended) combined with or without supplemental phytase (500 units Natuphos®/kg). Each diet was fed to 12 replicate pens with 40 male Ross × Ross chicks per pen for 9 weeks. Low dietary NPP significantly decreased body weight gain at 3 weeks of age but had no effect at 6 and 9 weeks of age. Supplemental phytase significantly increased body weight at 6 and 9 weeks of age. Feed conversion ratio was improved (p</it> < 0.006) in broilers at 9 weeks of age when rations at all three NPP levels were supplemented with phytase. Percent livability also improved with phytase supplementation (p</it> < 0.004). Percent tibial dyschondroplasia (TD) (determined in a live bird subsample) was decreased with phytase supplementation of all three NPP diets at both 3 and 9 weeks of age.