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 design to determine the effect of roasting or NaOH treatment of barley on ruminal fermentation and site and extent of digestion of nutrients. Experimental treatments were rolled barley, roasted (exit temperature, 135 degrees C) and rolled barley, and treated with 4% NaOH and 220 L of H2O/tonne of barley. Diets also consisted of grass silage and soybean meal. Treatment with NaOH reduced concentrations of several AA, starch, 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 reduced 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 tended to have a detrimental effect on feed intake, digestibility, and milk production. Roasting of barley did not appear to affect the site or extent of carbohydrate digestion, but roasting protected N from ruminal degradation. The protective effect on the carbohydrate fraction would be expected to be greater if the grain were cooled prior to rolling so that the protein matrix of the starch granule remained intact.