Pea proteins for piglets : effects on digestive processes

White-flowered pea ( Pisum sativum ) contains 20 to 25% crude protein (Nx6.25). The pea proteins consist in globulins (60%) and albumins (25%). Because the pea albumin proteins have biological activities due to their metabolic roles in the seed, some of them are called antinutritional factors (ANFs) for monogastric animals. These are mainly protease inhibitors and lectins. The apparent ileal digestibility of N and amino acids of raw peas fed to piglets was low. The N apparent ileal digestibility of pea protein isolate consisting mainly of globulins without ANFs was 15 units higher. The addition of 3% of pea ANF concentrate decreased the N apparent ileal digestibility by 7 units. This effect is not entirely due to the alleged antinutritional activities of die protease inhibitors or the lectins. This was suggested by the results of the incorporation of another pea ANF concentrate with a higher ANF content than the former concentrate. The albumin proteins themselves were suspected to be low digestible. This was illustrated by the results of a mathematical study of the amino acid composition of ileal digesta from piglets fed a raw pea diet, showing that these amino acids would be mainly of "endogenous + bacterial" origin and partly of dietary origin and especially of albumin type. No relations, neither between N digestibility and pancreatic protease activity in the pancreatic tissue, in its secretions or in the small intestinal digesta, neither between the activities in these different sections of the gastro-intestinal tract could be established. The trypsin and chymotrypsin activity decreased in the jejunal digesta and increased in the ileo-caecal digesta upon addition of pea ANF concentrate to a pea protein isolate diet although the N apparent ileal digestibility was not affected. The enzyme activities in the pancreatic tissue was decreased with a raw pea diet compared to a pea protein isolate diet although equivalent activities were found in the pancreatic secretions. These observations suggested that the mode of action of pea protease inhibitors may depend on the demand of proteases to hydrolyse the dietary proteins in the upper intestine, and on the nutritional quality of the dietary proteins associated with these protease inhibitors.