Effect of Phytase on Ileal Amino Acid Digestibility, Nitrogen Retention and AMEn for Broilers Fed Diets Containing Low and High Phytate Phosphorus

Abstract

A 42 d broiler experiment was conducted to determine the effect of added Escherichia coli phytase (Phyzyme-XP 5000G) to low and high phytate P (PP) diets on performance and nutrient digestibility. The experiment consisted of 12 treatments with 2 levels of PP: 0.24% low-phytate (LP) group and 0.32% highphytate (HP) group. Both LP and HP groups had respective positive controls (PCS) with 0.39% in the starter and 0.29% NPP in the grower, respectively, and 5 basal diets with graded levels (0, 250, 500, 750 and 1000 FTU’s/kg diet) of added phytase. The PP level in the HP diets was increased by substituting part of the corn and soybean meal with canola and rice bran. Ileal GE digestibility and GE retention were significantly higher in the PCLP group compared to the PC-HP fed group. Ileal GE digestibility at d 42 was lower in the HP groups and increased with the addition of phytase. A PP x phytase interaction was detected for ileal GE retention at d 21, due to a significant phytase response in the LP groups, but no response in the HP groups. In contrast, at d 42 a significant PP x phytase interaction was detected for ileal GE retention due to a significant response to phytase addition in the HP groups, but not in the LP groups. The % ileal digestibility of threonine, tryptophan, and serine were affected by PP levels and phytase, with a significant interaction of PP and phytase for 21 d broilers, and cystine for 42 d broilers. In general, interactions of phytase and PP for ileal digestibility of specific amino acids were due to a lack of positive response to phytase when added to the HP diet for 21 d broilers, compared to improvements in ileal digestibility of all amino acids (P=0.1284) in either the HP or LP fed broilers at d 42. The slight improvement of ileal digestible amino acids seemed to correlate with a 6.2 percentage point improvement in ileal N digestibility for 42 d broilers fed either the LP or HP diets. Broilers fed the LP PC diet had a higher % ileal nitrogen and energy digestion than broilers fed the HP PC diet at 21 d but there was no difference in 42 d broilers fed different PP levels. In summary adding phytase to broiler diets improved energy utilization by 2.1-4.9% for both LP and HP fed broilers and an improved ileal total AA (TAA) digestibility by 1.9-6.1% for LP fed broilers.