Counteraction of the growth depression of raw soybean oil meal by amino acid supplements in weanling rats

Effect of variable protein contents in diets containing Phaseolus vulgaris beans on performance, organ weights and blood variables in piglets, rats and chickens

A comparison was made of the effects of antinutritional factors present in Phaseolus vulgaris on piglets, rats and chickens. Also the hypothesis of whether the negative effect on weight gain due to the inclusion of raw Phaseolus vulgaris in the diet can be attributed to an insufficient supply of amino acids was tested. Test diets containing 200 g raw Phaseolus beans/kg were balanced for digestible protein and amino acids; in one diet extra casein was incorporated. The main response criteria were live-weight gain and the weight of various organs including the intestine. Live-weight gain in piglets was markedly reduced during feeding 200 g raw Phaseolus vulgaris/kg in the diet, but not in rats and chickens. Addition of casein did not improve the weight gain of the piglets, indicating that a toxic factor was responsible for the reduced weight gain and not an insufficient supply of amino acids. The weights of the spleen and thymus were markedly reduced in the piglets when the diets with raw Phaseolus beans were given, but not in the rats and chickens. Additional supply of casein did not change this effect. Indications were found that when the supply of dietary protein is adequate there is no reduction in pancreas weight with raw Phaseolus beans as was observed in previous experiments. The weight of the intestine was increased in all three species due to feeding raw Phaseolus vulgaris.

Studies of the digestibility and retention of nitrogen and amino acids in rats fed raw or heated soy flour

Apparent digestibility and absorption of nitrogen and amino acids from raw and heated soy flour were studied in rats. The apparent digestibility of all the amino acids from raw soybean was lower than from the heated flour. The net absorption was also significantly lower in the group fed raw soy flour for most of the amino acids, with the exception of cystine and methionine. The pattern of the amino acids along the digestive tract showed that while the levels of amino acids from heated soy flour started to decline in the jejunum and continued to decline in the ileum, in the group fed raw soy flour, the decline in levels of the amino acids did not begin until the ileum. The delay in the absorption might affect the overall absorption and utilization of the amino acids, and might explain the lower percentage retention of total nitrogen and amino acids in the carcasses of rats fed raw soy flour as compared with those fed heated soy flour. Possible reasons for the markedly lower cystine retention (relative to other amino acids) in the carcasses of the raw-soybean-fed rats are discussed.

A further physiological role for naturally occurring trypsin inhibitors: the evidence for a trophic stimulant of the pancreatic acinar cell

The oral ingestion of naturally occurring purified trypsin inhibitors from soybean, ovomucoid, and bovine pancreas has been demonstrated to be a potent stimulus to pancreatic digestive enzyme synthesis. This effect may be so marked as to lead to impairment of growth in the rat and chicken through the faecal loss of essential amino acids. This is thought to be due to the markedly potentiated secretion of pancreatic digestive enzyme protein overwhelming the normal digestive capacity of the gastrointestinal tract and resulting in a pancreatogenous protein-losing enteropathy. Experimental evidence is presented to suggest that this response to the trypsin inhibitors requires the mediation of the gastrointestinal tract and is independent of vagal innervation to the pancreas. The most satisfactory hypothesis would favour the release of a trophic stimulus from the intestinal mucosa (possibly pancreozymin-cholecystokinin) to the acinar cell of the pancreas in response to the presence of the trypsin inhibitor in the bowel lumen. It is suggested that a primary function of the endogenously secreted pancreatic trypsin inhibitor may be to potentiate enzyme synthesis by the acinar cell, providing an important stimulus for the repletion of the digestive enzymes. Some of the potential physiological and clinical implications of such a mechanism are discussed.