Resumen:
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.