174 Effects of dietary analyzed calcium to phosphorus ratio on growth performance, carcass characteristics, and bone mineralization of 26- to 127-kg pigs fed diets containing phytase

Abstract

Abstract Our objective was to determine the effects of feeding different analyzed calcium to phosphorus (Ca:P) ratios on performance of growing-finishing pigs from 26 to 127-kg fed diets containing 1,000 phytase units (FYT). A total of 1,215 barrows and gilts (PIC 359×Camborough, initial BW 26 ± 0.71 kg) were used in a 114-d growth trial with 27 pigs/pen and 9 pens/treatment in a randomized complete block design. The 5 dietary treatments were formulated to contain 0:75:1, 1.00:1, 1.25:1, 1.50:1, and 2.00:1 analyzed Ca:P ratio. Diets contained 1,000 FYT of Ronozyme HiPhos 2500 (DSM Nutritional Products, Inc., Parsippany, NJ) with assumed release values of 0.15% available P and 0.132% standardized total tract digestible P (STTD P). All diets were corn-soybean meal-based and formulated to contain approximately 122% of NRC (2012) STTD P estimates for the weight range across all 4 dietary phases. Treatments were achieved by increasing calcium carbonate at the expense of corn while maintaining a constant level of monocalcium phosphate. Data were analyzed with pen as the experimental unit, using generalized linear and nonlinear mixed models which included quadratic polynomial, broken-line linear, and broken-line quadratic models. Increasing analyzed Ca:P ratio increased (quadratic, P < 0.05) ADG, final BW, and ADFI (quadratic, P < 0.10). Feed efficiency improved (linear, P < 0.05) with increasing analyzed Ca:P ratio up to 2.00:1. Hot carcass weight (HCW) increased (quadratic, P < 0.05) and carcass yield decreased (quadratic, P < 0.10) with increasing analyzed Ca:P ratio. Bone mineralization increased (quadratic, P < 0.05) with increasing analyzed Ca:P ratio. The maximum responses in ADG, G:F, HCW, and bone ash were estimated at 1.63:1, 1.05:1, 1.11:1, and 1.25:1 analyzed Ca:P ratio, respectively. In conclusion, the estimated analyzed Ca:P ratio requirement for growing-finishing pigs from 26 to 127-kg fed diets containing 1,000 FYT ranged from 1.05:1 to 1.63:1 to maximize growth rate, G:F, HCW, and bone mineralization.