DIGESTIBILITY OF PROTEIN, AMINO ACIDS, PHOSPHORUS, CALCIUM AND ENERGY IN SORGHUM-SOYBEAN MEAL DIETS ADDED WITH PHYTASE IN PIGS

Phytates in grains and soybean meal (SBM) interact with phosphorus (P) and calcium (Ca), preventing their use. These molecules can also interact with amino acids (AA), proteins, and starch, affecting digestibility. In this study an experiment was conducted to determine whether in addition to raising the apparent ileal digestibility (AID) of P and Ca, phytase also improves AID of crude protein (CP) and AA, as well as fecal digestibility (FD) of gross energy (GE). Ten barrows (initial BW 18.6 +/- 1.3 kg), fitted with cannulas at the distal ileum, were assigned to five diets (treatments) in a 5x5 replicated Latin square design. Treatments (T) were: T1) control diet with sorghum-SBM plus inorganic P (+IP); T2) basal diet, sorghum-SBM without inorganic P (-IP-FTU); T3, T4 and T5 were the basal diet plus 250, 500 and 1000 phytase units (FTU) kg(-1) of feed (-IP+FTU). Absorption and AID of P and Ca increased, and excretion decreased (p <= 0.05) by phytase addition to basal diet. P and Ca excretion were higher in diet +IP than in -IP-FTU or the -IP+FTU (p <= 0.01). FD of GE increased (p=0.043) with phytase, but the increase was less than 1 %. AID of CP was higher in diets -IP-FTU than in +IP (p=0.009), but was not affected by addition of phytase (p=0.192). These results suggest that phytase addition to sorghum-SBM diets improves AID of P and Ca, but did not change that of CP and AA of growing pigs; phytase levels higher than 500 FTU kg(-1) of feed additionally increased the absorption of P and Ca.