Doctor of Philosophy (PhD)
Animal Science (Animal, Dairy, and Poultry Sciences)
This research was conducted with broilers to investigate the interactive effects of P and Ca on P requirement, digestibility, utilization, and phytase efficacy. Each treatment had a minimum of 6 replications. One experiment with 3 trials was conducted to identify the nonphytate P (nPP) requirement of 0 to 14 d old broilers. The nPP levels fed ranged from 0.30 to 0.60% with a Ca:nPP of 2.22:1 or 1.9:1. Requirement estimates for 0 to 14 d ranged from 0.52 to 0.60% nPP. One experiment with 2 trials was conducted to identify the nPP requirement of 14 to 28 d old broilers. The nPP levels fed ranged from 0.25 to 0.55% with a Ca:nPP of 1.9:1, 2.22:1, or 2.5:1 or set Ca at 0.90%. The requirement estimate was 0.45% nPP. An experiment with 2 trials was conducted to estimate the optimal Ca:nPP for 0 to 18 d old broilers and to investigate Ca and P digestibility and utilization at varying Ca:nPP. The nPP levels fed ranged from 0.30 to 0.50% with Ca:nPP of 1.9:1, 2.2:1, or 2.5:1 (trial 1) and 0.50% nPP with Ca:nPP of 1.5:1, 1.7:1, 1.9:1, or 2.1:1 (trial 2). Optimum Ca:nPP was 1.9:1 for 0 to 18 d old broilers. Digestibility and utilization of Ca and P decreased with increasing nPP and Ca:nPP. Two experiments were conducted to investigate any effect of starter nPP on growth performance and bone characteristics in subsequent growth phases. Feeding below the nPP requirement for 0 to 14 d resulted in better adaptation to a lower nPP in the grower phase. Feeding above the nPP requirement for 0 to 21 d resulted in a decrease in ADG at 35 d and G:F at 49 d. One experiment was conducted to compare the relative bioavailability of 2 Escherichia coli phytases. Retained P was higher for broilers fed Finase, which was more bioavailable than Optiphos. One experiment was conducted to investigate the influence of Ca level on the efficacy of phytase. Calcium level did not influence phytase efficacy. The results of these experiments suggest that dietary Ca influences the utilization of P but does not affect phytase efficacy.
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Powell, Syrena, "The Interactive Effects of Phosporus and Calcium on Phosphorus Requirement, Utilization, and Phytase Efficacy in Poultry" (2009). LSU Doctoral Dissertations. 483.