Soybean meal (SBM) inclusion is limited in swine diets due to the presence of anti-nutritional factors (ANFs) and non-starch polysaccharides (NSPs), which interfere with digestion, lowering the nutritional value of SBM. Low protein diets with synthetic amino acids further lower SBM inclusion in swine diets. Phytase, protease, carbohydrase, and acid treatment differentially reduce ANFs and NSPs in SBM. While each of these is used extensively in swine diets, the optimal combination of exogenous enzymes with or without acid that enhances the value of SBM for all pigs is unknown. Despite record-high corn prices, SBM inclusion will continue to be limited.
The overall goal of this project is to identify the optimal combination of exogenous enzymes with or without acidifiers to improve the nutritional value of SBM by mitigating the negative effects of soy ANFs and NSPs.
In the in-vitro digestion study, 18 different enzyme combinations with phytase, multi-carbohydrase, protease, and keratinase were tested to determine the most effective degradation of the anti-nutritional factors in SBM, such as allergenic protein and oligosaccharides. Regarding the degradation rate of crude protein and allergenic proteins (glycinin and ß-conglycinin), Treatment #17 (phytase 100ppm, carbohydrases 500ppm, protease B 250ppm, and keratinase 25ppm) was selected as the best for degrading the anti-nutritional factors present in SBM. In the feeding trial, a total of 240 pigs (average BW: 5.9 kg) weaned at 18 days of age were used to evaluate the mitigating effects of the selected enzyme combination with or without an acidifier on nursery pigs fed high SBM diets. Experimental diets included low SBM diet (SBM 17% in phase 1 and 20% in phase 2), standard SBM diet (SBM 22% in phase 1 and 25% in phase 2), high SBM diet (SBM 30% in phase 1 and 35% in phase 2), high SBM diet with selected enzyme combination (100 ppm of phytase, 500 ppm of multi-carbohydrase, 250 ppm of protease, and 25 ppm of keratinase), and high SBM diet with multienzyme and acidifier (0.5%) supplementation. Experimental diets were provided in the first 2 phases of a 3-phase feeding program: phase 1 (week 1), phase 2 (week 2 and 3) with a common corn-SBM based diet provided to all pigs in phase 3 (week 4 to 6). Pigs fed high SBM diets with multienzyme or with multienzyme and acidifier tended to have 12.5% greater (P=0.08) average daily gain because of greater (P<0.05) average daily feed intake compared to pigs fed high SBM diet during phase 2. During phases 1 and 2, pigs fed high SBM diets supplemented with multienzyme or multienzyme plus acidifier had less incidence of diarrhea (fecal score 3, 4; ?2 < 0.05) than those fed high SBM diet. Dietary treatment did not affect the serum concentration of thyroid and growth hormone and immunoglobulins. Pigs fed high SBM diet with multienzyme and acidifier supplementation had lower (P<0.05) concentration of secretory IgA in the ileal digesta on day 14 compared to high SBM diet (24.2 vs. 33.8 mg/ml) but similar to low SBM diet (22.7 mg/ml). Pigs fed high SBM diet with multienzyme and acidifier supplementation had 12% greater (P<0.05) jejunal villus height to crypt depth ratio on day 7 compared with low SBM.
In conclusion, supplementation with multienzyme or multienzyme and acidifier in high SBM diets could reduce the negative impact of high SBM inclusion in nursery pig diets by improving growth performance, promoting intestinal health, and reducing allergenic response in nursery pigs. The application of multienzyme or multienzyme with acidifier could increase the inclusion level of SBM in nursery pig diets from 17-20% to 30-35% during 0 to 3 weeks post-weaning, representing about a 50% greater inclusion of SBM in nursery pig diets