Non-phytate phosphorous requirements of egg laying pullets from 9 to 12 weeks of age and carryover effects of phosphorous deficiency at 18 weeks of age

The non-phytate phosphorous (nPP) requirement of 9 to 12-week-old laying hen pullets was investigated using body weight gain (BWG), mortality corrected feed conversion ratio (FCRm), tibia ash percent (TAP) and tibia ash weight (TAW). The same pullets were transferred back to a standard diet and monitored for longer-term responses to the reduced nPP feeding over 9 to 12 weeks at 18 weeks of age. A total of 672 9-wk-old Hy-Line W36 laying hen pullets were distributed across 42 cages and randomly assigned one of seven dietary treatments (0.13, 0.16, 0.20, 0.23, 0.26, 0.29, and 0.32% nPP, and 0.90% calcium). At 12 wk of age 3 pullets per pen were euthanized for fat-free tibia ash determination. Data were analyzed using ANOVA in JMP Pro 16.0 ( P ≤ 0.05). If significant differences were noted, single-slope broken line regression analysis was completed for BWG, FCRm, TAP and TAW. Only TAW responded to low nPP feeding generating a nPP requirement for 9 to 12 wk old laying hen pullets of 0.18% nPP. Body weight, FCRm and TAP were all unaffected by low nPP feeding. Remaining pullets from the 0.13, 0.16, 0.20 and 0.32% nPP treatments were maintained in their respective cages and phase- fed common corn-soybean meal diets from 12 to 18 wk of age. There were no carryover effects of feeding low phosphorous diets on pullet body weight or tibia ash at 18 wk. These data indicate that the nPP requirement for pullets from 9 to 12 wk of age is lower than current commercial recommendations based directly on TAW and indirectly by a lack of response to BWG, FCRm and TAP and pullets provided adequate nPP diets after a nPP deficiency from 9 to 12 wk were able to recover by 18 wk of age.