Phosphorus bioavailability, growth performance, and nutrient balance in pigs fed high available phosphorus corn and phytase

Three experiments were conducted to evaluate P bioavailability, growth perf ormance, and nutrient balance in pigs fed high available P (HAP) corn with or without phytase. The bioavailability of P in normal and HAP corn relativ e to monosodium phosphate (MSP) for pigs was assessed in Exp. 1. In a rando mized complete block design, 96 pigs (average initial BW 9.75 kg) were fed eight diets for 28 d. The reference and test diets were formulated by addin g P as MSP, HAP, or normal corn at 0, 0.75, or 1.5 g/kg to a cornstarch-soy bean meal basal diet (2.5 g/kg P) at the expense of cornstarch. Plasma inor ganic P concentration responded linearly (P < 0.05) to supplemental P intak e. Estimates of P bioavailability from HAP and normal corn when plasma P wa s regressed on supplemental P intake were 46 and 33%, respectively. In Exp. 2 and 3, pigs were fed corn-soybean meal-based diets containing HAP corn o r normal corn and 0 or 600 units of phytase per kilogram in a 2 x 2 factori al arrangement (two corn sources and two levels of phytase). In Exp. 2, 48 crossbred pigs (barrow:gilt, 1: 1) averaging 9.25 kg were used to evaluate growth performance. There were no detectable interactions between corn sour ce and phytase for any of the performance criteria measured. Pigs receiving normal corn had the lowest (P < 0.05) BW and rate of gain. Feed efficiency was lower (P < 0.05) in pigs fed normal compared with those fed the HAP co rn phytase-supplemented diet. In Exp. 3, 24 crossbred barrows averaging 14. 0 kg were used to evaluate nutrient digestibility. There were no detectable interactions between corn and phytase for any of the N and Ca balance crit eria. Nitrogen and Ca retention were improved in pigs receiving HAP corn wi th phytase (P < 0.05). Retention and digestibility of P was lowest (P < 0.0 1) for pigs on normal corn diet without phytase. The percentage of P digest ed and retained was improved and fecal P excretion lowered (P < 0.05) by fe eding HAP corn. The results of this study indicate that the bioavailability and balance of P in HAP corn is superior to that of normal corn. The addit ion of 600 phytase units (Natuphos 600, BASF) to HAP corn-based diets furth er improved P digestibility and reduced P excretion in pigs.