NUTRITIONAL-VALUE FOR SWINE OF SOYBEAN PRODUCED BY ISOPROPYL-ALCOHOL EXTRACTION

Three experiments were conducted to compare the nutritional value of s oybean meal produced by extraction with 95% isopropyl alcohol (IPA) or hexane (HEX) for swine. The same batch of soybeans and the same proce ssing equipment were used to produce both soybean meals. Analyzed cont ents of the IPA and HEX meals were, respectively: CP, 48.7, 47.0%; lys ine, 3.11, 3.06%; urease, .24, .13 Delta pH. In Exp. 1, two soybean me als and dietary lysine at .90 or 1.25% were used in a 2 x 2 factorial arrangement of treatments. Corn-based diets were fed to 32-d-old pigs for 26 d. There were no dietary lysine x soybean meal interactions (P greater than or equal to .35). Increasing dietary lysine increased (P < .001) ADG and gain/feed, but soybean meal source did not affect perf ormance. In Exp. 2, the nutritional value of HEX and IPA meals were ev aluated in a N balance study using 34-kg barrows and isonitrogenous co rn-based diets containing equal N from either HEX or IPA. Apparent tot al tract N and DM digestibility were similar for both diets. Nitrogen retention (14.4 vs 13.7 g/d, P < .10) and apparent biological value (5 6.5 vs 54.5%, P < .05) were slightly higher for HEX than for IPA. The effect of feeding HEX and IPA meals on morphological changes of small intestine in pigs weaned at 21 d of age was investigated in the last e xperiment. At 28 d of age, weaned pigs that were fed diets containing either HEX or IPA and unweaned control pigs were killed for the examin ation. Villus height and lamina propria depth at the duodenum were sim ilar among all treatments. At the jejunum, weaned pigs had smaller (P < .05) villus height and greater lamina propria depths (P < .001) than unweaned pigs. Dietary soybean meal source did not affect villus heig ht, but lamina propria depth was less (P < .10) for pigs fed IPA. The results of these experiments indicate that soybean meals produced usin g IPA or HEX as the solvent have equal nutritional value for swine.