THE BENEFICIAL-EFFECTS OF A MICROBIAL FEED PHYTASE IN DIETS OF BROILER-CHICKENS AND DUCKLINGS

Experiments with growing chickens and ducklings were designed to test the efficacy of a microbial feed phytase in releasing phosphorus (P) in diets based on sorghum and soybean meal. CaHPO4 was added in significant amounts to two of the five diets (4 and 5). For chickens, there was an overall improvement with phytase addition of P retention of 18%. Growht rate, feed intake, feed efficiency, nitrogen retention, tibia ash and tibia P all showed a significant improvement. Benefits tended to be less or not at all on the two diets (4 and 5) with added CaHPO4. For ducklings, overall improvement with phytase additions on P retention was 29%. On diets without CaHPO4, tibia ash, feed intake and growth rate but not FCR were improved. Diets 4 and 5 showed fewer or no response to the addition of phytase. Using a slope-ratio assay and bone ash (g) as the criterion of response, availability of P for ducklings in soybean meal was 58%.