Influences of the artificial variation of pancreatic juice returned to the duodenum on nutrient digestion in the small intestine of ruminant

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The main objective was to elucidate the relationships between the pancreatic exocrine secretion and the nutrient digestion in the small intestine of ruminant. Seep were implanted the catheters to the common and bile ducts, and fitted with the duodenum, abomasal, and ileal cannulas. In experiment 1, the sheep fed a diet were infused the pancreatic juice of 0 to 300% of the collected volume. Similarly, in the experiment 2 for abomasal infusates of starch (100 g/d) and casein (50 g/d), the return rate was artificially varied. The results were as follows. 1. The volume of secreted pancreatic juice decreased with increasing the return rate, but the daily protein secretion did not change. 2. The increased return rate of the juice quadratically raised the concentration of digestive enzymes, although the daily secretion of the enzymes was nearly constant. 3. The artificial variation of lipase and nuclease did not affect the digestion of lipids and RNA. 4. Protein digestion reached a plateau at 25% of the return rate. 5. The relationships between the return rate (X%) and starch digestion (Y g/d) could be expressed as Y = 0.61X + 59.1 (R^2=0.96, P<0.001). 6. The daily secretion of α -amylase when sheep ingested legume hay at 1.8 x the maintenance was increased by 2.5 fold than when sheep ingested grass hay at the maintenance level. In conclusion, the small intestinal digestion of starch over 5.8 g/d per metabolic body size may be limited by the secreted α -amylases in spite of the secretion variable with feed.