Raw and Heat-Treated Soybeans for Growing-Finishing Swine, and their Effect on Fat Firmness

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Abstract
Two experiments with growing- finishing swine were conducted to re-evaluate raw and heated unextracted soybeans as supplementary sources of protein to corn in a typical corn-soybean meal ration. In general, the performance of pigs fed heated soybeans, expressed as average daily gains and efficiency of feed utilization, was equal, if not superior, to that of pigs fed SOM as supplemental source of protein. Supplementary DL-methionine (0.25%) significantly improved the rate of gain when added to a diet containing cooked soybeans when compared to a similar diet with no added methionine. Chlortetra-cycline added at the level of 10 mg/lb. of diet failed to improve a raw soybean diet where the entire growing finishing period was considered. As compared to the carcasses of hogs fed the corn-SOM rations, the feeding of soybeans at the minimum levels required to balance the protein furnished by corn, resulted in less firm carcasses as measured by a higher iodine number, a softer consistency, and a higher refractive index of the backfat. The carcass data obtained indicate that feeding raw or heated unextracted soybeans had no consistent effect upon the fatness of the carcasses.