Abstract
The first aim of this study was to examine the effects of strain and age on phytate phosphorus (PP) utilization and intestinal phytase activity (IPA) in two strains of laying hens, Hy-line Brown (HB) and Hy-line White W-36 (HW) at 32, 52 and 72 weeks of age. A digestion trial was conducted using the indicator method and birds were sampled to measure IPA. The second aim was to examine the effect of feed grade exogenous phytase enzyme on total (TP), water soluble (WSP) and phytate phosphorus (PP) excretion in the HW strain fed varying levels of phosphorus. Hens were fed three concentrations of available P (AP): 0.2, 0.3 and 0.4%. Each level of P was supplemented with three levels of commercial feed grade exogenous phytase enzyme (0, 300, and 600 FTU/kg) and the amount of TP, WSP and PP in excreta per 100 g of feed consumed was calculated. The HB retained more PP as compared to HW. Intestinal phytase activity showed a significant (P<0.01) age effect with the highest activity occurring at 32 weeks. There were significant differences in the amount of TP and SP excreted between birds receiving the 3 levels of phosphorus with 300 units phytase (P<0.01). The results of this study showed that layers are capable of utilizing PP, and that utilization is regulated by IPA and varies with age. Exogenous phytase improved PP utilization but it increased the amount of TP and WSP in excreta.