The effect of feeding high concentrations of cholecalciferol, phytase or the combination on broiler chicks and laying hens fed various concentrations of nonphytate phosphorus

Two broiler chick and one laying hen experiments were conducted to determine the effects of feeding high concentrations of cholecalciferol (D 3 ), phytase (PHY) or the combination on the respective bird group (broiler chick or laying hen) fed various concentrations of nonphytate phosphorus (nPP) on performance, tibia ash and total tract phosphorus retention. The first broiler experiment utilized a completely randomized design with a 5 × 3 factorial arrangement of treatments consisting of five dietary concentrations of nPP (0.20, 0.26, 0.33, 0.39 and 0.45%) and three of D3 (0, 7,500 and 15,000 IU/kg) fed from day 5 to 23. The second broiler experiment was arranged as a 4 × 2 × 2 factorial in a completely randomized design resulting in four dietary concentrations of nPP (0.15, 0.25, 0.35 and 0.45%), two of PHY (0 and 1,000 FTU/kg), and two of D3 (0 and 7,500 IU/kg) fed from day 4 to 18. Ross 308 broiler chicks were housed in battery cages in an environmentally controlled room with ad libitum access to feed and water. Body weight gain (BWG) and feed efficiency (FE) were calculated over the duration of the each broiler experiment. Tibia and excreta samples were collected at the end of each experiment to determine bone ash, expressed as total ash weight (AshW) and as a percentage of total tibia weight (AshP), and total tract phosphorus retention (TTPR). In experiment one, a main effect of nPP resulted in significant (P &le 0.05) increases in BWG, AshW, and AshP. There was a significant D3 × nPP interaction (P &le 0.05) for FE and TTPR. Supplementation of D3 improved FE up to 0.39% dietary nPP, while FE peaked at 0.26% dietary nPP and remained constant for the non&ndashsupplemented diets. A quadratic effect was observed in TTPR with supplemental D3 (at both levels), while inconsistent results in TTPR were noted for the non&ndashsupplemental diets. The results of experiment one suggest that although D3 increased the TTPR, this increased P retention had little effect on bird performance. In experiment two, there were main effects of PHY and nPP that resulted in significant (P &le 0.05) increases in BWG and FE. A significant (P &le 0.05) PHY × nPP interaction was observed in both AshW and AshP. As expected, PHY was more efficient in improving tibia ash at lower concentrations of nPP than with higher concentrations of nPP. A significant (P &le 0.05) three-way interaction among D3 × nPP × PHY occurred in TTPR due to a low P retention value of chicks fed the non&ndashsupplemented 0.45% dietary nPP. The addition of higher concentrations of D3 to boiler diets was able to effectively improve phosphorus retention in experiment one, but did not affect the performance of chicks in either. As expected, phytase supplementation had a positive effect on performance of chicks fed low nPP diets. A laying hen experiment was conducted to investigate the effects of feeding high concentrations of D3 and PHY to 240 42-week-old Hy-line W-36 laying hens fed no supplemental inorganic P on bird performance (egg production, feed intake, hen weight), egg shell quality, tibia ash and TTPR. The experiment consisted of five dietary treatments arranged in a randomized complete block design and was conducted over a 12 week period. Treatments consisted of a positive control diet formulated to contain 0.46% nPP, a negative control diet formulated to contain 0.12% nPP, the negative control diet supplemented with 300 FTU/kg of PHY, 7,500 IU/kg of D3 or the combination of both PHY and D3 . Hens were housed in high rise single tier cages in an environmentally controlled room with ad libitum access to feed and water. Egg production (EP), feed intake (FI), hen weight (HW), dry shell weight (DSW), shell thickness (ST), specific gravity (SG) were determined over the duration of the experiment. Tibia and excreta samples were collected at the end of the experiment to determine tibia ash, expressed as AshW and AshP, and TTPR. There was a significant (P \u3c 0.01) treatment effect for FI and HW, while a significant (P \u3c 0.02) treatment effect was observed over time for HW. Hens fed the positive control diet consumed 4 g more of feed per day than those fed the negative control, supplemental PHY or D3 diets, and 8 g more of feed per day than those fed the combination diet. Hens fed the positive control diet were overall significantly (P &le 0.05) heavier than those fed the supplemented PHY, D3 or the combination diets. Hens fed the negative control diet supplemented with D3 or the combination weighed less than those fed the positive control diet during the last six weeks of the experiment. A significant (P \u3c 0.0001) treatment effect was also seen in TTPR. The diet supplemented with D3 and the diet with both D3 and PHY supplementation had very low phosphorus retention when compared to the other three diets. Significant treatment effects were not observed for all other parameters tested (EP, ST, DSW, SG, AshW, AshP). Analysis of total phosphorus concentration of the diets noted total phosphorus concentrations were elevated than the formulated values. This might explain the lack of significant treatment effects on performance, egg quality, tibia ash and why phosphorus retention had a lower than expected value. The results from these experiments suggest that higher concentrations of dietary D3 may not be a suitable substitute for supplementation of inorganic phosphorus