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Effect of Substitution of Wheat for Corn on Growth Performance and Digestibly in Nursing Pigs
The objective of this study was determine if wheat could substitute for corn, and if there was an optimal inclusion rate for wheat in nursery diets. A total of 144 pigs (48 pens, 3 pigs/pen) were blocked by weight and randomly assigned treatments within block. Following weaning (20 +/-3 d), pigs were fed a common phase 1 diet days 0-7d of the 35d study. Phase 2 diets were fed from day 7-21d and phase 3 diets were fed from days 21-35d. Phase 2 diets were formulated with either corn (52.9% of diet) or wheat (53.5% of diet) as the grain source. Both diets had 10% whey, 2.5% fishmeal, and 2.5% blood cells. Phase 3 diets were formulated with corn (64.3% of the diet) or wheat (65.3% of the diet) as the grain source. Diets in phases 2 and 3 were formulated to be isocaloric and isolysogenic (SID 1.35% in phase 2 and 1.23% in phase 3). All diets were formulated to meet or exceed the 2012 Swine NRC. Titanium dioxide was added as an inert marker in the diet of 0.3% to determine apparent digestibility of nitrogen, fat, and phosphorus. Within each phase the two diets where then blended in a ratio of 100:0, 80:20, 60:40, 40:60, 20:80 and 0:100% of the corn and wheat diets respectively. Pigs were weighed and feed disappearance was determined weekly. Fecal samples were collected from 17 to 21d and 31 to 35d for apparent digestibility determinations. Over the 35d study there was a quadratic effect of diet on BW (20.9, 21.3, 22.2, 21.7, 21.1, 21.2 kg, P<0.05, SEM 0.39). 7-35d there was a quadratic effect for ADG (485, 499, 532, 514, 491, 493 g/d, P<0.05, SEM 14). There was no difference in ADFI among treatments. There was linear effect of diet on G:F (0.68, 0.68, 0.71, 0.71, 0.70, 0.70, P<0.05, SEM 0.008) from day 7-35d with increasing wheat in the diet. Nitrogen and fat digestibility increased linearly from 72.5 to 83.9% for nitrogen (P<0.001, SEM 0.73) and 44.9 to 63.1% for fat (P<0.001, SEM 1.69) as the percent wheat increased in the diet in phase 3. There was a quadratic effect of diet on phosphorus digestibility (55.1, 56.5, 53.8, 54.6, 66.7 65.5%, SEM 1.18, P<0.0002). Wheat can be fully substituted for corn, without effecting growth performance of nursery pigs. Nitrogen, fat and phosphorus digestibility increases as the amount of wheat in the diet increases.
Keywords: Wheat, growth performance, digestibility