Rumen digestion and intestinal nutrient flows in sheep consuming pea seeds: the effect of extrusion or chestnut tannin addition

Different treatments aimed at reducing rumen degradability of pea protein were evaluated by in situ and in vivo measurements of rumen and intestine digestion of proteins. Four fistulated sheep were used. Pea seed provided 50% of dietary crude protein (CP) and was used raw (RP), with chestnut tannin (RPT2, 20 gkg -1 of pea CP; RPT3, 30 gkg -1 of pea CP), and extruded (EP). Rumen in situ degradability of pea protein was decreased by extrusion (83.3% vs. 90.8%) but was not affected by tannin addition. In vivo tannin addition did not affect the organic matter (OM) and N apparent digestibility, at the level of the rumen, the intestine or the whole tract. Extrusion decreased the apparent digestion of OM in the rumen but increased it in the small intestine. Total tract OM digestibility was not affected. Duodenal flow of non-ammonia N (NAN) increased by 27% between the RP and EP diet. This increase was mainly related to an increase in non-microbial N flow. Small intestine NAN apparent digestibility was not affected by extrusion and the amount of NAN apparently digested in the small intestine increased by 23% between the RP and EP diet. A slight decrease in total tract N digestibility was observed with extrusion. The efficiency of microbial protein synthesis was increased by extrusion. Small intestine apparent digestion of amino acids was greater for EP than for RP, but the profile of apparently absorbed amino acids was not affected. This study showed that low doses of tannins (up to 30 gkg -1 of pea CP, 15 gkg -1 of dietary CP) were inefficient in decreasing protein rumen degradability, however, the extrusion treatment largely increased the nitrogenous value of the pea seeds.