Effects of feeding either fresh alfalfa or alfalfa silage on milk fatty acid content in Holstein dairy cows

An experiment was conducted to examine effects of feeding either fresh alfalfa or alfalfa silage on milk fatty acid profiles in Holstein dairy cows. Sixteen multiparous cows (664.2±65.7 kg body weight; 187±56 days in milk) were used in a crossover design with two 5-week periods, with measurements being taken during week 5 of each period. Feed intake was higher (P=0.03) in cows consuming alfalfa silage compared with those cows fed fresh alfalfa. Milk yield and milk components were not affected (P>0.05) by dietary treatment. Proportions of myristic (C14:0) and palmitic (C16:0) acids were lower (P<0.05), and those of stearic (C18:0), oleic (C18:1), linoleic (C18:2n6) and linolenic (C18:3n3) acids were higher (P<0.05) in the milk fat of cows fed fresh alfalfa compared with those fed alfalfa silage. Feeding fresh alfalfa resulted in milk fat with a lower content of saturated, and a higher content of polyunsaturated fatty acids, compared with feeding alfalfa silage.