THE EFFECTS OF BARLEY PROCESSING ON NUTRIENT DIGESTION WITHIN THE GASTROINTESTINAL TRACT OF BEEF CATTLE FED MIXED DIETS

Abstract

The effects of grain ammoniation (5% wt/wt) on the site and extent of nutrient digestion by cattle were evaluated by feeding diets containing 50% barley grain and 50% brome-alfalfa hay. Grain treatments consisted of: (1) rolled barley (15% moisture), (2) ammoniated, whole barley (15% moisture), (3) rolled barley (30% moisture) and (4) ammoniated, whole barley (30% moisture). Four 622-kg Hereford steers with ruminal and intestinal cannulas were used in a Latin square design. Acid detergent lignin and chromic oxide were used as digestibility markers. Because the overall conclusion about the effects of barley processing was not affected by the specific marker used, digestibility coefficients were calculated as the means obtained with the two markers. Forestomach digestion of organic matter from ammoniated, whole barley was approximately six percentage units lower (P < 0.05) than that from rolled barley. The small intestine compensated by increasing (P < 0.10) organic matter digestion of ammoniated, whole barley. Large intestinal and total tract digestion of organic matter was not affected by any dietary treatment. Total tract digestion of crude protein was depressed (P < 0.05) approximately five percentage units by ammoniation. This depression occurred principally within the small intestine. Ammoniation increased digestibility of neutral detergent fiber by approximately five percentage units, virtually all within the forestomach. Because palatability problems were encountered feeding ammoniated, whole barley, and because nutrient digestion was not improved in comparison to diets containing rolled barley, ammoniation of barley grain can not be recommended except as a method of grain preservation prior to physical processing. Key words: Ammoniation, barley, gastrointestinal tract, cattle, processing, markers