BIOLOGICAL AVAILABILITY OF PHOSPHORUS IN DEFLUORINATED PHOSPHATES WITH DIFFERENT PHOSPHORUS SOLUBILITIES IN NEUTRAL AMMONIUM CITRATE FOR CHICKS AND PIGS

Two experiments were conducted to assess the bioavailability of P in five sources of defluorinated phosphate (DFP) that differed in P solubility in neutral ammonium citrate (NAC). In Exp. 1, 384 2-d-old male chicks were fed a corn-cornstarch-dextrose-soybean meal basal diet (1.22% lysine, 1.00% Ca, .45% P) or the basal with .05 or .10% P from monosodium phosphate (MSP), or .10% P from DFP with 60, 70, 75, 82, or 91% NAC soluble P. Each diet was fed to six pen replicates of eight chicks per pen for 14 d (58 to 402 g). Growth rate, feed/gain, and tibia breaking strength and ash concentration were improved (P < .001) by P supplementation, regardless of P source. Tibia strength and ash were regressed on P intake, and slope-ratios were calculated to assess the relative bioavailability of P in the DFP sources. The bioavailabilities of P in the 60, 70, 75, 82, and 91% NAC soluble DFP sources, relative to MSP (given a value of 100), were 81, 75, 84, 84, and 91%, respectively (linear, P < .08): In Exp. 2, 35 individually penned pigs were fed a corn-soybean meal basal diet (.95% lysine, .75% Ca, .33% P) or the basal with .15% P from MSP or from the five DFP sources. Each diet was fed to five pigs for 33 d (15.0 to 35.9 kg). Growth rate, feed/gain, and breaking strength of the metacarpals, metatarsals, and femurs were improved (P < .001) by MSP and DFP. The bioavailabilities of P in the 60, 70, 75, 82, and 91% NAC soluble DFP sources were 90, 80, 82, 90, and 87%, respectively (P > .25). From these results, a slight positive relationship exists between the NAC solubility of P and the bioavailability of P in DFP for chicks, but not for pigs.