The effects of various dietary levels of phytase and available phosphorus on performance of laying hens

Data previously obtained from our laboratory indicated that addition of 300 U of phytase/kg diet supported optimal long-term performance of laying hen s (20 to 70 wk) fed a corn-soybean meal (SBM) diet containing 0.10% availab le phosphorus (AP). Our primary objective was to determine if a phytase lev el lower than 300 units/kg is adequate for a commercial strain of Single Co mb White Leghorn laying hens (n = 504) fed a corn-SBM diet containing no su pplemental P (0.10% AP). Dietary treatments consisted of the corn-SBM basal diet (0.10% AP, 3.8% Ca, and 17% CP) supplemented with 0, 100, 200, 250, o r 300 U of phytase/kg, 0.05% inorganic P (0.15% AP), and a positive control diet containing 0.45% AP, Each of the seven dietary treatments was fed to six replicate groups of 12 hens from 20 to 60 wk of age. No significant differences in performance were observed among treatments du ring the first 8 wk of the experiment. By 28 wk of age, the 0.10% AP diet, with no supplemental phytase or P, resulted in significantly lower (P < 0.0 5) egg production and body weight compared with all other dietary treatment s. Feed consumption, feed efficiency, and egg yield were subsequently depre ssed by 32 wk of age in hens fed the 0.10% AP diet. No other significant di fferences among treatments were observed for performance averaged over the entire 40-wk experimental period. The mean daily AP intake of hens fed the 0.15% AP, 0.45% AP, and 0.10% AP + phytase diets was 155, 474, and 103 mg, respectively. The results of this study indicate that phytase improves the utilization of P in corn-SBM diets for laying hens and that com-SBM diets c ontaining 0.10% AP + 100 units of phytase/kg diet or 0.15% AP supported egg production performance that was not significantly different (P > 0.05) fro m that of hens fed a corn-SBM diet containing 0.45% AP.