Effects of phosphorus level and phytase in broiler breeder rearing and laying diets on live performance and phosphorus excretion.

The effects of a reduced dietary nonphytate phosphorus (NPP) level and inclusion of phytase on broiler breeder performance and P concentrations in the litter and manure were investigated. Ross 308 broiler breeder pullets and Ross 344 cockerels were placed sex-separate in a blackout growing house and fed standard starter and grower diets to 9 wk of age. At 10 wk of age, 4 treatments (A, B, C, D) were assigned to each of 4 floor pens of 68 pullets and 1 pen of 50 cockerels. From 10 to 21 wk, treatments A to D contained 0.37, 0.27, 0.27, and 0.17% NPP, respectively, with 300 phytase units (FTU)/kg of phytase added to treatments B and D. At 21 wk of age, birds were photostimulated and transferred to a two-thirds slat-litter breeder house with 16 pens of 60 pullets and 6 cockerels. A laying diet was fed from 22 to 64 wk and NPP levels of treatments A to D were adjusted to 0.37, 0.27, 0.19, and 0.09%, respectively, and phytase addition to treatments B and D was increased to 500 FTU/kg. Analysis of the litter from growing pens showed no effect on litter total P when phytase replaced 0.1% of NPP. However, decreasing the dietary NPP by 0.1% without phytase reduced the litter total P by 18%. Water-soluble P (WSP) and the WSP:total P ratio decreased when the grower dietary NPP level was reduced to 0.17% with added phytase and was correlated with litter moisture levels in growing pens. During the laying period, a reduction in NPP from 0.37 to 0.09% with added phytase reduced both the manure total P and WSP by 42%. Hen-day egg production was highest on the lowest NPP diet with phytase, but fertility decreased when the dietary NPP was reduced below 0.37%. Results showed that phytase inclusion in a broiler breeder laying diet at the expense of all added P from dicalcium phosphate reduced the manure total P and WSP concentrations by 42%, with no effect on the number of chicks produced per hen housed.