Effects of superdoses of phytase on peaking Hy-Line W-36 laying hen egg production and egg quality

    

New generations of feed enzymes are included to enhance nutrient utilization. This study was designed to evaluate the efficacy of a new generation phytase, HiPhorius (HP), and protease, ProAct 360, when fed to peaking hens. Dietary treatments included Positive Control (PC), Negative Control 1 (NC1) at 0.15% nPP, NC1+600 FYT/kg HP, NC1+900 FYT/kg HP, Negative Control 2 (NC2) with a 2% crude protein (CP) reduction, NC2+ProAct360, and NC1+600 FYT/kg HP+ProAct 360. A total of 378 Hy-Line W-36 hens were randomly allocated to nine replicate cages per treatment with six hens per cage. Peaking 1 and Peaking 2 diets were provided throughout the 17-wk study. Phytase activity was analyzed after feeding and were higher than expected. Phytase activity ranged from 1,391-1,508 FYT/kg in Peaking 1 and ranged from 1,112-1,365 FYT/kg in Peaking 2 diets. Considering the elevated phytase activity, the new objectives were to determine how superdoses of HP affected egg production and egg quality when fed to hens from 18-35 wk. The GLM procedure of SAS was used to analyze weekly performance in an ANOVA and then repeated measures ANOVA were conducted for 4-week periods (Pd; Pd1 = 18-21wk, Pd2 = 22-26wk, Pd3 = 27-30wk, Pd4 = 31-34wk). The MIXED procedure was used to conduct preplanned contrasts to compare PC vs NC1, NC1 vs diets containing HP, and PC vs diets containing HP. When considering the ANOVA for individual wk and the repeated measures ANOVA for each Pd, neither egg production (EP%) nor egg quality were affected by dietary treatment (P> 0.05). However, when contrasts were utilized, EP% differences were apparent. In Pd2 and Pd4, hens provided the PC had higher EP% than those hens provided the NC1 (p=0.013 and p=0.0082, respectively). As hens approached peak production in P2, those provided superdoses of HP tended to have higher EP% than those provided the NC1 (p=0.059). While dietary treatment did not affect EP% or egg quality in Pd3 (P> 0.05), hens provided diets containing HP had improved EP% compared to those provided NC1 (p=0.0072) in Pd4. In Pd1-P4, the EP% of hens provided treatments with superdoses of HP was similar to hens provided the PC (P> 0.05). These data support the inclusion of superdoses of HiPhorius in peaking diets with reduced nPP.

Key Words: phytase, protease, laying hens, phosphorus, crude protein.