The objectives of this study were to determine the availability of P from mineral phosphate sources by using different basal diets and measurement of P retention and prececal (pc) P digestibility as well as pc myo-inositol phosphate (InsP) degradation in broilers. Semi-synthetic and corn-soybean meal-based basal diets were used in experiment 1, and corn-based and wheat-based basal diets were used in experiment 2. Anhydrous monosodium phosphate (MSPa) or monocalcium phosphate monohydrate (MCPh) was supplemented to increment the P concentration by 0.05, 0.10, and 0.15% or by 0.075 and 0.150% in experiments 1 and 2, respectively. Titanium dioxide was used as an indigestible marker. Diets were pelleted through a 3-mm screen. In experiment 1, retention was measured based on total excreta collection from 20 to 24 d of age using 7 replicated birds per diet. In experiment 2, digesta from the terminal ileum was collected from 22-d-old broilers penned in groups of 19 with 5 replicated pens per diet. The P retention response to supplemented MSPa did not differ between the 2 basal diets in experiment 1. The response in pc P digestibility to MCPh supplements also did not differ between the 2 basal diets in experiment 2, as calculated by linear regression analysis. Hydrolysis of InsP6 measured on both the excreta and pc levels was high in the basal diets without a mineral P supplement. Mineral P supplementation significantly decreased (P < 0.05) InsP6 hydrolysis from the InsP-containing diets in both experiments. Thus, the choice of the basal diet did not affect the evaluation of the supplemented mineral P source. However, calculated values for mineral P sources need to be adjusted for the decline in hydrolysis of InsP contained in the basal diet that results from the P supplement.
Keywords: hydrolysis; inositol phosphate; phosphorus; prececal digestibility; retention.
©2014 Poultry Science Association Inc.