The effect of exogenous phytase supplementation on nutrient digestibility, ruminal fermentation and phosphorous bioavailability in Rambouillet sheep

BACKGROUND The effect of phytase supplementation with respect to a high sorghum grain diet on sheep voluntary feed intake, apparent nutrient digestibility, ruminal fermentation, phosphorus (P) excretion and blood serum P concentration was evaluated. RESULTS Phytase supplementation significantly decreased fecal P excretion ( P = 0.003), resulting in a 26% decrease in relation to the phytase free diet. Dry matter intake, nutrient digestibility, ruminal butyrate and serum P were not ( P > 0.10) affected by the phytase level. Neutral detergent digestibility showed a tendency to increase linearly ( P = 0.10) with increasing phytase levels. Ruminal pH was lower for phytase supplemented sheep, with a significant decrease ( P = 0.007) at 9 h post feeding, whereas ruminal ammonia‐N at 3 h post feeding was lower ( P = 0.004) for the phytase treatment groups, resulting in a decreasing linear response ( P = 0.001) with an increasing phytase dose. Duodenal pH was significantly reduced at 6 h post feeding. Propionate tended ( P = 0.051) to be increased linearly as the phytase supplementation level increased. CONCLUSION Exogenous phytase supplementation of high sorghum grain diets significantly decreased fecal P excretion in Rambouillet rams. Phytase supplementation appears to affect neutral detergent fiber digestibility, duodenal and ruminal pH, ammonia and propionate. © 2018 Society of Chemical Industry