A total of forty-eight grower pigs were used to evaluate the effects of feeding low phytic acid (LPA) corn, LPA soybean meal, normal corn (NC), normal soybean meal (NSBM), and phytase on nutrient digestibility and excretion. Barrows were distributed in blocks by initial BW and randomly assigned to 1 of 8 dietary treatments in a 2 × 2 × 2 factorial arrangement (6 pigs/treatment). Pigs were fed twice a day (0700 and 1700 h) at 3 times the ME requirement for maintenance. Phytase was added to the diet at 510 phytase units/kg of feed, and all diets were formulated to provide 0.39% total P, 0.50% Ca, and 1.0% lysine with no supplemental inorganic P. Experimental periods consisted in 7 days of adaptation to metabolism crates and dietary treatments, followed by a 3-d total collection of urine and faeces.
Total faecal DM excreted, percentage of DM of faeces, and percentage of DM digested were not different (P>0.53) among treatments. Fecal P excretion was reduced for pigs fed LPA corn vs. NC (2.85 vs. 3.24 ± 0.119 g/d; P=0.024), for pigs fed LPA soybean meal vs. NSBM (2.79 vs. 3.30 ± 0.119 g/d; P=0.007), for pigs fed phytase vs. nonphytase diets (2.80 vs. 3.29 ± 0.119 g/d; P=0.009), and for pigs fed LPA corn, LPA soybean meal, and phytase vs. NC and NSBM without phytase (2.16 vs. 3.70 ± 0.237 g/d; P<0.001). Phosphorus digestibility was increased for pigs fed diets containing LPA corn vs. NC (48.4 vs. 39.9 ± 2.27%; P=0.012), for pigs fed phytase vs. nonphytase diets (48.4 vs. 39.9 ± 2.27%; P=0.019), and for pigs fed the LPA corn, LPA soybean meal, and phytase diet vs. the NC and soybean meal diet (60.1 vs. 34.1 ± 4.5%; P<0.001). Corn type and soybean meal type had no effect (P>0.11) on water-soluble P excretion. However, pigs fed diets containing phytase tended to excrete less total water-soluble P than those without phytase inclusion (1.99 vs. 2.27 ± 0.099 g/d; P<0.066).
It is concluded that feeding any combination of LPA corn, LPA soybean meal, and phytase was additive, significantly improving P digestibility and dramatically decreasing P excretion to reduce the potential impacts of P from pig manure on the environment.
BE Hill, AL Sutton and BT Richert.2009. Journal of Animal Science. 87:1518-1527.