Effect of high concentration of phytase supplementation on energy and nutrient digestibility of growing pigs fed with reduced dietary crude protein balanced with limiting amino acids

There is a need to improve pig production at least cost through various dietary manipulations and nutrient management strategies that will foster reduced environmental wastes of N, amino acids (AA), P, and Ca. This experiment was designed to estimate the effect of phytase supplementation on energy and nutrient digestibility of growing pigs fed with reduced dietary crude protein (CP) balanced with limiting AA. Experimental diets were formulated in a 3 × 2 factorial arrangement of 6 dietary treatments containing 3 CP concentrations (14, 16, and 18%) supplemented with or without 5,000 units phytase/g. Limiting AA of the diets were balanced using crystalline Lys, Met, Thr, and Trp. The 6 experimental diets were fed to 6 cannulated growing pigs (30.00 ± 2.10 kg) in a 6 × 6 Latin square arrangement of 6 diets and 6 periods. Fecal and ileal samples were collected to estimate the apparent and ileal digestibility of nutrients and energy. Apparent total tract digestibility (ATTD) of dry matter (DM), N, crude fibre, ether extract, and energy decreased (P < 0.05) linearly as CP concentration increased in the diets. Apparent ileal digestibility (AID) and ATTD of N linearly decreased (P = 0.000) by increasing CP concentration in the diets from 14 to 18%. Increasing CP concentration linearly increased ATTD (P = 0.002) and AID (P = 0.003) of P. Greater ATTD and (AID) (P < 0.001) of nutrients and energy were observed with pigs fed diets supplemented with phytase. Apparent ileal digestibility of Lys, Met, Thr, Trp, and Glu decreased linearly and quadratically (P < 0.005) while, AID of Arg, His, Iso, Leu, Phe, Val, Ala, Asp, Cys, Gly, Pro, Ser and Tyr improved (P = 0.000) linearly and quadratically as dietary CP increased from 14 to 18 % CP. Dietary supplementation with phytase improved (P < 0.001) AID of all the essential amino acids. Arg, His, Ile, Leu, Asp, and Pro were not affected by CP and phytase interaction. Greater (P < 0.001) AID values were observed for all AA following phytase supplementation. It was concluded from the present study that 2 and 4% reduction in dietary CP balanced with Lys. Met, Thr, and Trp resulted in improved ATTD and AID of DM, N and AID of the supplemented AA in growing pigs. Pigs fed diets supplemented with phytase had better ATTD and AID of nutrients and energy than those fed without phytase supplementation.