Protein utilization and toxic effects of raw beans (Phaseolus vulgaris) for young pigs

One balance trial and two pair-feeding experiments were conducted to determine the effects of feeding raw small red beans (Phaseolus vulgaris) on dietary protein utilization, organ weights, pancreatic enzyme activities, blood variables and weight gain of young pigs. In the balance trial, the substitution of 5 and 15% raw beans for soybean meal and cornstarch in the semipurified diet depressed apparent digestibilities of crude protein, total S and all individual amino acids measured. Urinary excretion of N and sulfate was increased and N retention was decreased. Pigs fed a semipurified diet containing 15% raw red beans in one pair-feeding trial gained less and had slightly larger livers and slightly smaller spleens than did pigs fed the control diet without raw beans. There was no difference in pancreas size as a percentage trypsin, chymotrypsin and amylase activities were lower in those pigs fed the raw bean diet. Pigs fed the raw bean diet also had higher serum urea and lower albumin concentrations and higher alkaline phosphatase activities and plasma Zn concentrations. Pigs fed the raw bean diet had a higher total leukocyte count, primarily because of an increase in neutrophils; eosinophil numbers were depressed. Similar results were obtained in the other pair-feeding trial with pigs fed a practical corn-soybean meal diet with or without 15% raw beans; however, leukocyte numbers and differential counts were affected only slightly by the feeding of raw beans. Pancreatic size of pigs fed raw beans was decreased in this trial. The inclusion of raw red beans in the diet for young pigs did not cause pancreatic enlargement as it does in the rat or chick. The feeding of raw red beans decreased protein digestibility and appeared to interfere with systemic protein utilization.