Effect of Dietary Corn Starch Intake on Pancreatic Amylase and Intestinal Maltase and pH in Cattle

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Abstract
The pH optimum of pancreatic α-amylase from grain-fed steers was determined to be 6.9, while that of intestinal maltase was established at 5.8. Both assays were found to be linear up to 1 hr of incubation. The Vmax of pancreatic amylase was determined to be 1.15 mg of maltose monohydrate produced/hr. Activities of pancreatic and intestinal maltase were not reduced (P>.05) during the interval from sample collection from the animal until analysis 4 hr later when tissues were kept on ice. Twenty-four yearling Holstein steers fed either alfalfa hay at a maintenance level of metabolizable energy (ME) intake or corn at one, two or three times the maintenance ME intake level were slaughtered after being fed 106 days. The pancreas was removed along with sections of the intestine. Specific activity of pancreatic amylase for steers fed the high level of corn was 129% of that for steers fed the alfalfa diet (P>.05). Intestinal maltase activity was highest in the jejunum and decreased toward the ileum. Increasing dietary starch intake resulted in no response (P>.05) in maltase activity at 10, 30, 50, 70 or 90% of the small intestine length. The effect of dietary starch level on digesta pH was dependent on sampling location within the small intestine. There were no dietary effects (P>.05) on digesta pH for the first 10% segment of intestine distal to the pylorus. However, in all subsequent sections, digesta pH was higher (P<.05) for steers fed the alfalfa diet than for those fed the two higher levels of grain. A calculation for estimating the amount of pancreatic amylase needed to hydrolyze starch presented to the small intestine is discussed. Copyright © 1981. American Society of Animal Science . Copyright 1981 by American Society of Animal Science.