Ileal amino acid digestibility and performance of pigs fed grain sorghum-based diets supplemented with phytase

Two experiments were conducted to determine the effect of phytase supplementation to sorghum-soybean meal diets on the apparent ileal digestibility (AID) of amino acids (AA) and performance of growing pigs. In one experiment, six pigs (average initial BW 86.1kg) fitted with a simple T-cannula at the distal ileum, were fed three diets in a repeated 3x3 Latin square design. Diet I was the basal sorghum-soybean meal diet. Diets 2 and 3 were the basal diet supplemented with phytase at 500 and 1000 units of phytase activity (FTU/kg diet), respectively. There was no effect of phytase supplementation on the AID of AA (P>0.10). Arginine AID was highest and threonine AID was lowest. In the second experiment, 28 pigs (average initial BW 22.9kg) were allotted to four diets (seven replicates/treatment) in a randomized complete block design. Diets were: 1) sorghum-soybean meal, basal diet, 0.67% apparent ileal digestible lysine; 2) basal diet +350FTU/kg diet; 3) basal +700FTU; 4) basal +1050FTU. The basal diet contained 100% of the available P requirement for pigs 20-50kg. Linear regression analyses showed no effect of phytase supplementation on average daily gain (ADG; P=0.93), feed (P=0.37), lysine (P=0.37) and threonine (P=0.37) intakes, or feed conversion (P=0.54). Pigs fed the basal diet tended to have higher ADG than those fed diet 2 (P=0.09) or diet 3 (P=0.11). Results indicate that phytase supplementation does not affect the supply of digestible AA or, as a consequence, the performance of pigs fed sorghum-soybean meal diets.