Dry malt extract from barley partially replacing ground corn in diets of dairy cows: Nutrient digestibility, ruminal fermentation, and milk composition

ABSTRACT: Dry malt extract (DME) has been used in animal nutrition as an alternative source of rapidly fermentable carbohydrate. An experiment was conducted to evaluate the partial replacement of ground corn with DME in diets of dairy cows on apparent digestibility, ruminal fermentation, predicted rumen microbial protein supply, N excretion, serum urea-N concentration, and milk yield and composition. Twenty-eight Holstein cows (35.3 ± 5.88 kg/d milk yield and 148 ± 78 d in milk), 4 of which were rumen cannulated, were blocked according to the presence of rumen cannulas, parity, milk yield, and days in milk and enrolled into a crossover design experiment. Experimental periods lasted 21 d, of which the first 14 d were allowed for treatment adaptation and 7 d were used for data collection and sampling. Treatment sequences were composed of control (CON) or DME from barley (Liotécnica Tecnologia em Alimentos) replacing ground corn at 7.62% diet dry matter (~2 kg/d). Data were analyzed using the MIXED procedure of SAS (SAS Institute Inc.) modeling the fixed effects of treatment, period, and their interaction, in addition to the random effect of animal. Ruminal fermentation data were analyzed as repeated measures including time and its interaction with treatment in the previous model as fixed effects. Treatments did not affect nutrient intake or feed sorting. Dry malt extract increased apparent digestibility of CP. Feeding DME decreased ruminal pH and molar percentage of butyrate and increased molar percentage of acetate. No treatment effects were detected for predicted rumen microbial protein supply or N excretion. Cows fed DME had lower serum urea-N concentration than CON cows. Dry malt extract increased yields of actual milk, 3.5% fat-corrected milk, fat, and protein, and improved feed efficiency (fat-corrected milk ÷ dry matter intake). Cows fed DME had lower milk urea nitrogen content in comparison with CON cows. Dry malt extract can partially replace ground corn in the diet while improving milk yield and feed efficiency.