INFLUENCE OF ROASTING OR SODIUM-HYDROXIDE TREATMENT OF BARLEY ON DIGESTION IN LACTATING COWS

Three cannulated, lactating cows were used in a 3 x 3 Latin square des ign to determine the effect of roasting or NaOH treatment of barley on ruminal fermentation and site and extent of digestion of nutrients. E xperimental treatments were rolled barley, roasted (exit temperature, 135 degrees C) and rolled barley, and treated with 4% NaOH and 220 L o f H2O/tonne of barley. Diets also consisted of grass silage and soybea n meal. Treatment with NaOH reduced concentrations of several AA, star ch, and NDF in the barley. Starch digestibility in the rumen was lower for barley that was treated with NaOH but was unaffected for roasted barley. Digestibilities of N and starch in the small intestine were re duced for barley treated with NaOH, but values for rolled and roasted barley were similar. Apparent total tract digestibility of starch was reduced for the NaOH treated barley. Treatment of barley with NaOH ten ded to have a detrimental effect on feed intake, digestibility, and mi lk production. Roasting of barley did not appear to affect the site or extent of carbohydrate digestion, but roasting protected N from rumin al degradation. The protective effect on the carbohydrate fraction wou ld be expected to be greater if the grain were cooled prior to rolling so that the protein matrix of the starch granule remained intact.