Strategies to Reduce Fecal Phosphorus Excretion in the Broiler Industry Without Affecting Performance

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Title: Strategies to Reduce Fecal Phosphorus Excretion in the Broiler Industry Without Affecting Performance
Author: Plumstead, Peter William
Advisors: J. T. Brake, Committee Chair
J. A. Osborne, Committee Member
J. C. Allen, Committee Member
J. W. Spears, Committee Co-Chair
R.O. Maguire, Committee Member
Abstract: Total phosphorus (P) in broiler manure has been reduced by decreasing dietary non phytate P (NPP) in combination with added phytase or low phytate (LP) grains. However, few studies have investigated the effects of diet amendment on performance and P excretion from broiler breeders, while the reported effects on water soluble P (WSP) from broilers have been inconsistent. To address this, broiler breeders were fed reduced NPP diets and phytase during the rearing (10-21 wk) and laying (22-64 wk) phase (Chapter 1). Decreasing dietary NPP below 0.37% reduced fertility, which was hypothesized to result from insufficient P intake during rearing. Decreasing NPP in breeder laying diets to 0.19% (no phytase) or 0.09% (with phytase) had no effect on eggs or chicks produced, but reduced manure total P and WSP by 39 to 42%, respectively. Chapters 2, 3, and 4 investigated reduced available P (AvP), phytase, phytate level, and the calcium (Ca):AvP or Ca:NPP ratios in broiler diets on ileal P and amino acid (AA) absorption, P retention, and total P and WSP in manure. Reduced AvP and phytase decreased manure total P. However, manure WSP and the ratio of WSP:total P were controlled by the dietary Ca:AvP ratio. Effects of Ca:AvP on WSP were dependent on the initial dietary phyate level and were mediated by altered phytate hydrolysis, precipitation of CaP complexes and urinary P output. Including LP soybean meal (SBM) in diets decreased total P and WSP by 49% and 56%, respectively, while phytase increased the WSP:total P ratio in manure. Maximum P retention and minimum total P output occurred when the dietary Ca:NPP ratio was 2.34:1 and 2.53:1 in LP and high phytate (HP) SBM diets, respectively. Dietary Ca had no effect on amino acid (AA) absorption in HP SBM but decreased AA absorption in LP SBM diets when Ca was >0.93%. Therefore, while a wider Ca:NPP ratio could decrease manure WSP, this may negatively affect AA absorption when diets contain LP SBM.
Date: 2007-07-04
Degree: PhD
Discipline: Poultry Science

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