INFLUENCE OF AMMONIATION OF HIGH MOISTURE BARLEY ON ITS IN SITU RUMEN DEGRADATION AND INFLUENCE ON RUMEN FERMENTATION IN DAIRY COWS

Abstract

High-moisture barley (HMB) was ammoniated at levels of 0, 0.65, 1.30, and 1.95% of dry matter (DM) and stored in 6-t lots in large plastic silage bags. In situ rumen degradation rate of DM in HMB decreased with increased level of ammoniation, nitrogen component degradation was little influenced, and neutral detergent residue degradation increased. Three dairy cows with large rumen cannulae were fed totally mixed diets twice daily in five experimental periods. Diets contained 490 g kg⁻¹ oat silage, 385 g kg⁻¹ HMB, and 125 g kg⁻¹ of a protein-mineral-vitamin supplement. Measurements were made from weeks 18 to 33 of lactation to determine effects of ammoniation of HMB on levels and patterns of feed intake, as well as parameters of rumen fermentation. Cows tended to eat diets more rapidly as ammoniation level of substituted HMB increased, although total DM intake was not influenced. Rate of decline of rumen pH, and accumulation of butyrate, post-feeding was less pronounced as level of ammoniation of substituted HMB increased, supporting reduced rate of rumen degradation of HMB. However, total extent of change was greater, perhaps reflecting more rapid feed consumption post-feeding. Increased rumen acetate and butyrate concentrations as well as reduced concentration of 3 methyl butyrate suggests greater rumen fiber fermentation may have occurred as level of ammoniation of substituted HMB increased. Key words: Cows (dairy), ammoniation, high-moisture barley