The variation throughout a year in the fatty acid composition of milk fat from 2 dairy herds

Summary Differences in milk-fat composition in summer and winter have been demonstrated and related to feeding for an autumn calving Friesian herd and an Ayrshire herd in which calving was equally divided between spring and autumn. The observations are in agreement with previous results obtained for milk fat in the Northern Hemisphere. Summer milk fat contained more C 18 acids and less C 4 –C 16 acids than winter milk fat, the effect being particularly marked for the autumn calving herd. Changes in the pattern of feeding altered the fatty acid composition of milk fat from both herds, and abrupt changes in feeding were clearly reflected even at times when stage of lactation effects were greatest.