Effect of wheat as a feedstuff in starter diets on nursery pig growth performance and digestibility

Two studies were conducted to determine if corn can be replaced by wheat and if wheat can be combined with corn distillers dried grains with solubles (DDGS) and a commercial carbohydrase in phase 2 and 3 nursery diets. In Exp. 1, 144 pigs were blocked by weight and randomly allotted to 6 dietary treatments: 0%, 20%, 40%, 60%, 80%, and 100% wheat replacing corn. In Exp. 2, 210 pigs were blocked by weight and randomly allotted to 5 dietary treatments: control diet (CO); 30% wheat (W); wheat with carbohydrase (W + Enz); 30% wheat with 30% corn DDGS (WCD); and WCD with carbohydrase (WCD + Enz). In both experiments, pigs were fed a standard phase 1 diet from d 0 to 7 post-weaning. In both experiments, TiO2 was used as an indigestible marker to determine apparent total tract digestibility (ATTD) of N, ether extract (EE), gross energy (GE), P, neutral detergent fiber (NDF), and acid detergent fiber (ADF). In Exp. 1, there was a quadratic effect of increasing wheat on overall (d 0-35) average daily gain (ADG, P < 0.05). There was a linear effect of increasing wheat on gain to feed ratio (G:F, P < 0.05). Overall there were no changes in average daily feed intake (ADFI). Apparent digestibility of N, P, and ADF increased with increasing wheat in phase 2 (P < 0.05). The digestibility of N, EE, GE, P, and NDF increased linearly with increasing wheat in phase 3 (P < 0.05). In Exp. 2, the ADG of pigs fed W did not differ from the control, while those fed WCD had greater gain (P < 0.05). Pigs fed the diets supplemented with carbohydrase had reduced ADG (P < 0.05) compared to the unsupplemented diets. There was an increase in N, P, and GE digestibility with DDGS diets in phase 2 (P < 0.001). Carbohydrase supplementation increased N, EE, ADF, and NDF digestibility in phase 2 (P < 0.01), and ADF and NDF digestibility in phase 3 (P < 0.01). In phase 3, P digestibility increased and GE digestibility decreased when DDGS was added. The results demonstrate that wheat can be fully or partially substituted for corn in nursery diets. In this study, the addition of carbohydrase enzymes improved nutrient digestibility, but resulted in poorer growth performance.