Influence of Age on Utilization of Raw Soybean Meal by Chickens

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Abstract
The effects of raw soybean meal in chickens of different ages were studied in 3 separate experiments. In one experiment, raw and heated soybean meal diets were fed to chicks at various ages up to 12 weeks of age for a period of 2 weeks. In the other experiment, the experimental diets were fed to one-day-old chicks for 8 weeks. In the last experiment, the experimental diets were fed to 30 week-old laying hens for 8 weeks. Criteria used were growth, feed efficiency, pancreas weights, nitrogen retention and egg production. Growth of chickens that were 6 weeks of age or more before being fed raw soybean meal was not affected by the active principle in the raw meal that depresses growth of younger chicks. Pancreatic hypertrophy was evident in chicks that showed no growth depression, but was greatly reduced in birds at 12 weeks and completely absent in hens fed raw soybean meal. The egg production, feed utilization and nitrogen retention of hens fed raw meal was no different than that of the hens fed heated soybean meal diet. Results support the concept that raw soybean meal has an active fraction which cannot be fully digested by the young chick because of the lack of specific enzyme(s) and that a part of this protein is absorbed which acts in a positive manner to produce pancreatic hypertrophy. This active fraction is hydrolyzed by enzymes produced by the older birds, hence produces no physiological effects which are observed in young chicks.
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