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Gastrointestinal Tract pH and Starch in Feces of Ruminants¹

Purdue University, West Lafayette, IN47907

Abstract

Three trials were conducted to study the relationship between pH in the gastrointestinal tract, fecal pH and starch in the feces of ruminants fed high energy diets. In all trials, fecal pH values were similar (P>.10) to those obtained for ingesta taken from the small intestine and colon, but higher (P<.01) than values obtained from the abomasum. Cattle and sheep fed non-buffered all-concentrate diets had intestinal pH values which were considerably lower than the 6.9 necessary for optimal activity of pancreatic alpha amylase. Low fecal pH was associated with large amounts of starch in feces of cattle fed high concentrate rations. The correlation coefficients relating fecal pH to starch in feces were —.82 and —.94 (P<.01), respectively, for the two cattle trials. Addition of limestone or magnesium limestone to high energy diets fed to cattle increased (P<.01) intestinal pH approximately 1.0 pH unit and decreased (P<.01) starch in feces from about 32% to 9% due presumably to a more favorable pH for pancreatic alpha amylase activity in the lower gastrointestinal tract.

¹ Journal Paper No. 6198 of the Purdue University Agricultural Experiment Station.

² Department of Animal Sciences.

³ Present address: U.S.D.A., A.R.S., Nutrition Institute, Ruminant Nutrition Laboratory, Beltsville, MD 20705.