0
In the exp.1, a 3 x 2 factorial arrangement of treatments was used to investigate the response of growing pigs to supplemental phytase (0, 600, or 1,200 units/ kg) in low- or adequate-protein diets (160 or 200 g/kg). Diets were purposely deficient in non-phytin P as a robust test of response to phytase supplementation. Seventy-two pigs with an average initial BW of approximately 10 kg were selected and assigned to individual stainless-steel pens. Pigs were allowed free access to diets and water for 28 d during which BW and feed intake were recorded weekly. 12 pigs (growth) or 6 pigs (N utilization) per diet were used to test the hypothesis that phytase ameliorates dietary protein effects on growth and nutrient balance. Pigs were fed the experimental diets for a 5-d adjustment period followed by a 5-d collection period in which there was total, but separate, collection of feces and urine. In the exp.2, a 2 x 2 factorial arrangement of treatments was used to investigate the response of growing pigs to supplemental phytase (0 or 1,200 units/kg) in low- or high-phytin P diets (2.2 or 3.9 g/ kg). Forty-eight pigs with an average initial BW of approximately 20 kg were selected and assigned to individual stainless-steel pens. Pigs were allowed free access to feed and water for 28 d during which BW and feed intake were recorded weekly. Eight crossbred barrows (28 to 30 kg) were surgically fitted with a simple T-cannula approximately 10 cm cranial to the ileo-cecal junction. Were used to test the hypothesis that increased phytin depresses nutrient utilization and phytase addition ameliorates these effects.
In the exp.1, pigs fed diets containing 160 g of protein/kg gained BW slower and less efficiently (P<0.01) than those fed diets containing 200 g of protein/kg. Phytase supplementation of the 160 g of protein/kg diet did not affect BW gain; however, at the 200 g of protein/kg of diet, there was a linear improvement in BW gain with Aspergillus niger phytase addition (P<0.05). In the nutrient balance study, feeding the 160 g of protein/kg of diet depressed (P<0.01) percent N absorbed. Likewise, N retention was reduced (P<0.05) in pigs fed the 160 g of protein/kg of diet. Phytase supplementation of these low-phytin P diets resulted in predictable improvements in digestibility of P (P<0.01). In the exp.2, dietary phytin concentration did not elicit a response in any measure of pig growth performance. However, phytase supplementation improved (P<0.05) BW gain of pigs regardless of dietary phytin concentration. P digestibility was greater (P<0.01) with phytase supplementation regardless of dietary phytin concentration.
In conclusion, phytase supplementation significantly enhances P utilization, but does not affect the apparent ileal or total tract digestibility of DM, energy, CP, or AA.
J. S. Sands, D. Ragland, R. N. Dilger, and O. Adeola. 2009. Journal of Animal Science. 87:2581-2589.
