INFLUENCE OF AMMONIATION OF, HIGH-MOISTURE BARLEY ON DIGESTIBILITY, KINETICS OF RUMEN INGESTA TURNOVER, AND MILK PRODUCTION IN DAIRY COWS

Abstract

Three dairy cows with large rumen cannulae were fed totally mixed diets twice daily. Diets contained 49% whole crop oat silage, 38.5% high-moisture barley (HMB), and 12.5% protein-mineral-vitamin supplement on a dry matter (DM) basis. HMB had been ammoniated at target levels of 0, 0.65, 1.30, and 1.95 g per 100 g HMB DM. Actual levels achieved were 0, 0.63, 1.30, and 1.95 g ammonia per 100 g. Apparent digestibility of organic matter (OM), neutral detergent (ND) fiber, starch, and N were not significantly influenced by level of ammoniation of HMB, although there was a trend for increased N digestion. Total rumen pool sizes of wet ingesta and DM were not influenced by ammoniation levels of HMB, although proportion of ND fiber in rumen OM declined as level of ammoniation of HMB increased. Milk yield and production of milk protein and lactose increased as level of ammoniation of HMB increased. Data are interpreted to suggest that rumen digestion of dietary nonfiber components declined as level of ammoniation of HMB increased, although digestion of ND fiber was not influenced. These results support the hypothesis that ammoniation of HMB shifted the site of digestion of a portion of the dietary nonfiber component from the rumen to the intestine without influencing rumen microbial pool sizes or degradative activity. Greater energetic efficiency of intestinal digestion of dietary nonfiber components, as level of ammoniation of HMB increased, may have contributed to the increased milk yield. Key words: Barley (high-moisture), ammoniation, dairy cows, digestion