Use of carbohydrases in corn-soybean meal-based nursery diets

Three experiments were conducted to test the hypothesis that supplementing nursery pig diets with a mixture of carbohydrases (CS) will improve pig performance and nutrient digestibility. The CS used in these experiments contained 7 units/g of alpha-1,6-galactosidase, 22 units/g of beta-1,4-mannanase, beta-1,4 mannosidase, and trace amounts of other enzymes. In Exp. 1, 108 pigs weaned at d 21 of age were fed one of three diets containing 0 (control), 0.1, or 0.2% CS for 5 wk, based on a three-phase feeding program (1, 2, and 2 wk). Over the entire 35-d period, ADG was not affected (P > 0.05) by treatment, but supplementing 0.1% CS increased (P < 0.05) gain:feed by 9%. Experiment 2 used 10 gilts fitted with simple T-cannula in the terminal ileum at 3 wk of age. After cannulation, pigs were fed the same control Phase I and II diets, but the Phase III diet contained either 0 or 0.1% CS. Ileal samples were collected for the 3 d following the 5-d adjustment period during Phase III. Apparent ileal digestibility of GE, lysine, threonine, and tryptophan was greater (P < 0.05) in the CS diet. In Exp. 3, 90 pigs weaned at 21 d of age were fed the same control Phase I and II diets, but the Phase III diet contained either 0 or 0.1% CS. Phase III diets were fed for 3 wk. Average daily gain of the CS group was greater (P < 0.05) than the control group during wk 3. Gain:feed ratio was greater (P < 0.05) for the carbohydrase group during the entire Phase III period. Four pigs per treatment were killed at the end of Exp. 3 to measure villus height and to determine the concentration of raffinose and stachyose in different parts of the gastrointestinal tract. Average villus height was greater (P < 0.05) in pigs fed the CS diet. Carbohydrase supplementation decreased (P < 0.05) the concentration of stachyose in freeze-dried digesta from the proximal and distal small intestine. Raffinose concentration, on the other hand, was decreased (P < 0.05) by CS supplementation only in the distal small intestine. These lower concentrations suggest that CS improved the digestibility of carbohydrate in soybean meal. In conclusion, the addition of CS to Phase I and Phase II nursery diets containing low levels of soybean meal did not improve pig performance, but its addition to corn-soybean meal-based Phase III nursery diets improved gain:feed ratio and energy and AA digestibility.