Effect of high-dose phytase and low calcium concentration on performance of broiler chicken given diet severely limited in nonphytate phosphorus

Abstract

The effect of phytase and calcium ( Ca ) was investigated on performance of broiler chickens given diets severely limited in nonphytate phosphorus ( NPP ). A total of 550 ten-day-old broiler chickens were allocated to 10 diets from 11 to 40 d of age. There were a positive control (with adequate Ca and NPP concentration) and 9 diets (with 1.4 g NPP/kg) consisting of Ca (5.6, 4.2, and 2.8 g/kg) and phytase (0, 1,500, and 3,000 FTU/kg) in a 3 × 3 factorial arrangement of treatments with 5 pens per treatment. Increasing phytase dose linearly increased BW ( P < 0.001) and tibia ash ( P < 0.001) and reduced feed-to-gain ratio ( F:G , P < 0.001) and mortality ( P < 0.05). Increasing phytase dose quadratically affected tarsometatarsus strength ( P < 0.001) and tibia ash percentage ( P < 0.05). Decreasing Ca concentration linearly increased BW ( P < 0.001) and reduced F:G ( P < 0.001), mortality ( P < 0.01), and tibia ash ( P < 0.05). In terms of BW ( P < 0.05), F:G ( P < 0.01), mortality ( P < 0.05), tibia ash ( P < 0.05), and tarsometatarsus strength ( P < 0.01), response to phytase addition was greater for high Ca concentrations, resulting in a Ca × phytase interaction. Generally, increasing phytase dose or decreasing Ca concentration in severely low NPP diet has beneficial effect on BW, F:G, and mortality of broiler chicken. If performed in combination, performance results improve even more. Nonetheless, when phytase is supplemented in the diet, decreasing Ca concentration does not allow maximum bone strength and ash.