Influence of supplemental phytase on growth performance, digestion and phosphorus balance of lambs fed sorghum-based diets

Phosphorus excretion in lambs from urine and faeces is considerably high due to elevated concentration of grains in the diets. This study evaluated the effect of supplemental phytase on in vitro dry matter degradation (IVDMD), feed intake, growth performance, total tract digestion and phosphorus (P) balance in finishing lambs fed sorghum-based diets. An exogenous phytase mixture was added at dosage of 0, 750, 1500 and 2250 FTU (phytase units) per kg diet as fed. Thirty-two finishing lambs (21.5 +/- 2.2 kg body weight) were randomly assigned to those diets and fed for 60 d. The P concentration in the diets varied between 2.0 to 2.4 mg/kg dry matter (DM). Inclusion of phytase in the diet had no effect on IVDMD. However, total tract digestion of DM, NDF and P were linearly (P<0.01) improved as phytase level increased. Phosphorus intake and excretion (urine and faeces) were not affected (P>0.05) by phytase, but P retention showed a linear increment as the enzyme increased in the diet. Growth performance of lambs was not affected by phytase. Therefore, phytase supplementation improved P digestion and retention, but it did not change P excretion and growth performance in finishing lambs fed sorghum-based diets.