Sodium bioavailability from phosphate sources.

Abstract

Two experiments were conducted with day-old broiler chicks from 1 to 21 days of age to measure the relative bioavailability of sodium from three commercially available defluorinated phosphates and two reagent sources (monosodium and dibasic sodium phosphate) compared to sodium chloride as the standard. Ten chicks were assigned to each pen in the first experiment and eight chicks in the second. Each diet was fed to three pens of males and three pens of females within an experiment. Feed-grade sodium chloride was added to a basal feed containing dicalcium phosphate in increments of .05% (0 to .25%) to provide total sodium levels from 180 to 967 ppm. Each of the defluorinated materials was substituted into the dicalcium basal at a level sufficient to provide one-half of the supplemental phosphorus. Reagent phosphate sources were added to the basal in amounts sufficient to supply .059% sodium, the same amount as provided by .15% sodium chloride. Reagent grade ammonium chloride was added to treatment diets to ensure a level of .156% total chloride. Mortality was related to sodium level and was excessive only for the treatment receiving no supplementation. Significant manure moisture increases were associated with up to .10% supplemental sodium chloride. Slope-ratio calculations of sodium availability, using body weight and daily sodium intake, revealed average availability values over the experiment ranging from 83.9 to 89.8% for the three defluorinated sources. Availability for monobasic sodium phosphate was calculated to be 91.8%, while that of the dibasic source was somewhat higher at 97.2%.