Effect of ethanol in feed on milk flavor and chemical composition.

A crossover study was performed using 24 dairy cows to investigate whether pure ethanol in concentrations that could be found in well-fermented silages influenced milk composition or flavor. Cows were fed a standard ration of well-fermented grass silage for ad libitum intake and high moisture barley and a protein concentrate in restricted amounts. A daily dose of ethanol (600 g) was divided into three meals/d and fed with grass silage. When cows received ethanol, milk yields decreased slightly, but milk fat and protein concentrations increased so that energy-corrected milk yield increased by 0.9 kg/d. Milk concentrations of lactose and urea decreased, concentrations of ethanol and acetone increased, concentrations of free fatty acids increased slightly, and alpha-tocopherol concentrations were unaffected. The proportion of palmitic acid in milk fat increased, and the proportion of unsaturated acids decreased. Organoleptic milk quality was reduced because of an increase in milk tainted by feed flavors. The off-flavor could not be attributed solely to the ethanol transmitted to the milk. Precautions should be taken to avoid extensive production of ethanol during fermentation of grass silage and other feeds that are to be fed to dairy cows.