Abstract
Abstract An experiment was conducted to test the hypothesis that lowering dietary Ca and P reduces gastric pH and diarrhea of weanling pigs, but microbial phytase overcomes negative effects of low Ca and P on growth performance and bone ash. A total of 320 weanling pigs (6.35 ± 0.87 kg) were allotted to 8 corn-soybean meal-based diets in a randomized complete block design with 5 pigs/pen. Two phase 1 (d 1 to 14) control diets contained 100 or 50% of total Ca and digestible P relative to the requirement, and 6 diets in which 500, 2,000, or 16,000 units/kg of phytase was added to each control diet were formulated. Common diets were fed in phases 2 (d 15 to 27) and 3 (d 28 to 42). Fecal scores were recorded in phase 1 and growth performance data were recorded within each phase. Gastric pH was measured in 1 pig/pen on d 14; on d 14 and 42, the right femur of 1 pig/pen was collected. Data were analyzed using contrast statements in SAS. Results indicated that during phase 1, lowering Ca and P did not reduce gastric pH or fecal score, but the 50%-diets reduced (P < 0.05) average daily gain and average daily feed intake of pigs compared with the 100%-diets (Table 1). Phytase above 500 units/kg increased (P < 0.05) gain:feed ratio and tended (P < 0.10) to decrease gastric pH. Pigs fed the 50%-diets had reduced (P < 0.05) bone ash at d 14 and 42 compared with pigs fed the 100%-diets regardless of phytase inclusion level. In conclusion, reducing Ca and P in diets for weanling pigs does not decrease gastric pH or fecal score, but compromises growth performance and bone mineralization. However, super-dosing of phytase increases G:F of pigs regardless of dietary Ca and P concentration.
Accepted Version
Published Version
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