Effects of raw pea flour on nutrient digestibility and immune responses in the preruminant calf

Two milk substitute diets for which the protein was provided either exclusively by skim milk powder (control) or partially (34%) by dehulled raw pea flour were given for 2 and 4 wk, respectively, to five preruminant calves, each fitted with a reentrant ileocecal cannula. Ileal apparent digestibility was lower with the pea diet during wk 1 than with the control diet. Four of the cannulated calves exhibited significant intolerance to the pea diet, resulting in lower digestibility during wk 4. In contrast, fecal digestibility of the pea diet, measured in four additional calves without reentrant cannulas, did not significantly decrease between wk 1 and 4. The AA composition of ileal digesta from the first group of calves did not vary greatly, suggesting that the differences observed in their apparent digestibility of proteins were due mainly to changes in the loss of endogenous proteins. However, pea legumin survived digestion in the small intestine in amounts generally equivalent to 1 to 3% of intake. Most of that undigested fraction was smaller than the native legumin: 40 to 200 kDa instead of 360 kDa. Also, a 45-kDa fragment was detected in the urine. Increased intestinal permeability could have favored the development of the high systemic anti-pea antibody titers that were observed in all of the calves.