Broiler Breeder Manure Phosphorus Forms Are Affected by Diet, Location within Pen, and Period of Accumulation.

Phosphorus (P) modifications of poultry diets have successfully decreased total P (TP) in litters and manures, but impacts on water-soluble P (WSP_M) in broiler breeder manure have been unclear.  Our objectives were to: (1) characterize P constituents of breeder manures as affected by dietary P modification, location within the pen, and manure accumulation period and (2) determine the impacts that P forms and moisture content in breeder manures had on the variability in WSP_M concentration.  Two diets were formulated with and without phytase to attain 0.40% available P (AvP) during the breeder laying phase (22 to 64 wk).  Manure was collected after accumulation periods of 48 h, 3 wk, and 39 wk in locations under the feeder, the drinker, and the common area between the drinker and feeder.  Forms of P in manure from these breeders were characterized by solution ³¹P nuclear magnetic resonance.  Breeders fed phytase with simultaneous non-phytate P reduction produced manures with 15% lower TP, but did not change WSP_M when averaged over manure accumulation periods and locations within the pen.  Manure WSP increased linearly as manure moisture increased regardless of diet, location within the pen, or accumulation period (r² = 0.76).  After 39 wk of accumulation, orthophosphate was 91% and phytate was 6.7% of the manure TP.  As manure accumulation periods increased (48 h < 3 wk < 39 wk), manure TP concentrations increased (11.9 < 13.2 < 17.3 g kg^-1), orthophosphate proportions increased (73.2% < 80.1% < 91.0%), and phytate proportions decreased (23.1% > 17.0% > 6.7%).  The mineralization of phytate and other organic complexes presumably contributed to the increased orthophosphate and TP.  Optimum phosphorus management of breeder manures should consider the impact of drinking water management on WSP_M and the manure sampling location on TP and WSP_M determinations.