True phosphorus digestibility of black-eyed pea and peanut flour without or with phytase supplementation in broiler chickens

Two studies were conducted to determine the true P digestibility (TPD) of black-eyed pea (BEP) and peanut flour (PNF) and the TPD response to phytase supplementation using the regression method. Sequential diets containing 115, 230, or 345 g of BEP/kg (experiment 1) and 115, 230, or 345 g of PNF/kg (experiment 2) without or with 1,000 units of phytase/kg were formulated. Chromic oxide was added to the diets at the rate of 5 g/kg as an indigestible marker. At 20 d posthatch in each study, 384 male broiler chickens (Ross 708) were weighed and allotted to the diets with 8 replicates of 8 birds each in a randomized complete block design. The birds had free access to the experimental diets until d 26 posthatch. In both studies, dietary P increase and phytase supplementation improved (P < 0.001) growth performance of the broiler chickens. There were linear increases (P < 0. 001) in ileal and excreta P output but a linear decrease (P < 0.001) in apparent P digestibility with an increase in dietary P levels. Phytase supplementation reduced (P < 0.001) ileal P and excreta P output and increased (P < 0.001) apparent P digestibility and retention. Apparent Ca digestibility was affected (P < 0.01) by P level and phytase addition in BEP and by P level (P < 0.05) in PNF. Apparent Ca retention in BEP increased (P < 0.05) with phytase addition. The TPD in the BEP increased (P < 0.01) from 29 without phytase to 83% with the addition of 1,000 units of phytase/kg. There was an increase (P < 0.01) in TPD of PNF from 67 without phytase to 75% with phytase supplementation. There was a corresponding increase (P < 0.01) in true P retention from 10% without phytase to 61% with phytase in birds on BEP diets and an equivalent increase (P < 0.01) in true P retention from 74% without phytase to 84% with phytase in birds that received the PNF diets.