Phosphorus requirements of grow-finish pigs raised in a commercial environment

We conducted three experiments to identify available phosphorus (aP) requirements of pigs reared in commercial facilities. In a pilot study (Exp. 1), 600 gilts (PIC, initially 95.2 lb) were randomly allotted to a low or high dietary P regimen in a 98-d study. Pigs were phase-fed six diets from 95 to 106, 106 to 150, 150 to 183, 183 to 212, 212 to 245, and 245 to 267 lb. Corresponding aP concentrations were: 0.30, 0.28, 0.27, 0.27, 0.24, and 0.19% (low) and 0.37, 0.33, 0.30, 0.28, 0.27, and 0.26% (high). No differences were observed (P > 0.10) in ADG and overall F/G was greater (P<0.07) for pigs fed the low aP regimen. In Exp. 2, 1,260 gilts (initially 74.5 lb) were randomly allotted to one of five dietary treatments in a 26-d study. Experimental diets contained 0.18, 0.22, 0.25, 0.29, or 0.32% aP, corresponding to 0.5, 0.6, 0.7, 0.8, or 0.9 g aP/Mcal ME. There were 28 pigs per pen and 9 pens per treatment. From d 0 to 14, increasing aP tended to increase (linear, P0.12). Pooled bending moment of the femur, 6th rib, and 3rd and 4th metatarsals increased with increasing aP (linear, P0.10) with increasing aP. In Exp. 3, 1,236 gilts (initially 195.1 lb) were randomly allotted to one of five dietary treatments in a 28-d study. Experimental diets contained 0.05, 0.10, 0.14, 0.19, 0.23% aP, equivalent to 0.152, 0.277, 0.402, 0.527, or 0.652 g aP/Mcal ME. From d 0 to 14, increasing aP increased (linear, P<0.01) ADG and F/G. However, from d 0 to 28 increasing aP had no effect (P>0.17) on growth performance. Increasing aP increased (linear, P