Effect of Phytase Addition on Growth and Carcass Traits of Pigs Fed Diets Deficient in Lysine, Calcium, and Phosphoruss1

One hundred fifty gilts (initial and final BW 20 and 107 kg, respectively) were used in a 106-d experiment to determine the effects on growth performance and carcass traits of phytase addition to diets deficient in Lys, Ca, and P. The treatments were 1) positive control [NRC adequate in amino acids (AA), ME, Ca, and P]; 2) a diet with 85% of the Lys of diet 1, but adequate in Ca and P (85L+CaP); 3) 85L+CaP with 500 phytase units/kg phytase, expected to supply Lys, ME, Ca, and available P (aP; 85L-CaP+Phy); 4) 85L-CaP+Phy but with no added phytase (85L-CaP-Phy); and 5) 85L-CaP-Phy but adequate in Ca and P (85L+CaP-E-AA). The nutrient matrix values used for the phytase addition were as follows: Ca 144%, aP 144%, ME 15,246 kcal/kg, Lys 12%, Met 5%, Thr 5%, and Trp 2%. The phytase was provided at 0.083% of the diet and therefore was expected to provide the following nutrients: Ca 0.12%, aP 0.12%, ME 12.7 kcal/kg, Lys 0.01%, Met 0.004%, Thr 0.004%, and Trp 0.002%. Treatment diets were fed in a 4-phase feeding program. The standardized ileal digestible Lys levels in the control were 0.91, 0.79, 0.69, and 0.57% for diet changes at 20, 44, 68, and 87 kg, respectively. Each treatment was replicated 5 times with 6 gilts each. Pigs fed diets with reduced Lys concentrations had lower daily gain (P < 0.01) than pigs fed the control diet. Pigs fed 85L-CaP+Phy had G:F equal to, or slightly greater, than pigs fed the control or 85L+CaP, but pigs fed 85L-CaP+Phy had greater G:F than pigs fed 85L-CaP-Phy (P < 0.05). Pigs fed a phytase-added diet with reduced levels of Lys, Ca, aP, and ME had G:F not different from, and slightly greater than, pigs fed the control or 85L+CaP. However, G:F was reduced in pigs fed 85L-CaP-Phy. Pigs fed 85L-CaP+Phy had greater lean and backfat than pigs fed 85L+CaP. Phytase addition increased bone-breaking strength, but not to the level of pigs fed the diets with added Ca and aP. In conclusion, phytase addition improved utilization of Ca and P and some data (but not all) suggest that phytase addition improved utilization of Lys and ME.