Effect of a novel plant phytase on performance, egg quality, apparent ileal nutrient digestibility and bone mineralization of laying hens fed corn-soybean diets

The efficacy of a novel transgenic corn-derived phytase (TCDP) and two other commercial microbial phytases (PA and PB) were compared in the long-term feeding study of laying hens. The treatments consisted of a positive control (PC) diet adequate in phosphorus (P, 0.32% nonphytate P, NPP); a negative control (NC) diet low in P (0.10% NPP); and an NC supplemented diet containing three phytase sources (TCDP, PA or PB) at two supplemental levels (500 or 5000 FTU/kg of diet). Eight diets were fed to Hy-line hens (n =576) from 50 to 66 weeks of age. We found that with a reduction in dietary Pin the NC diet, egg production, egg mass, feed intake, final BW, BW gain, eggshell thickness, and eggshell strength of laying hens decreased (P<0.05). In addition, the number of soft-shelled, cracked and broken eggs increased (P<0.05) in the NC group. The addition of TCDP, PA or PB significantly increased laying production and egg quality (P<0.05), and performed similarly in hens fed the PC diet. Hens fed each source of phytase had greater apparent ileal P digestibility, tibia ash, and bone breaking strength than hens fed the NC diet (P<0.05). The apparent ileal P digestibility increased as phytase level increased from 500 to 5000 FTU/kg of diet (P<0.05). Results from this study indicate that the addition of TCDP to a P-deficient diet improves laying performance, egg quality, ileal P utilization, and bone mineralization, and TCDP is as efficacious as two commercial microbial phytases when P-deficient diets for laying hens were supplemented with it. (C) 2013 Elsevier B.V. All rights reserved.