Comparative potential of white and red clover to modify the milk fatty acid profile of cows fed ryegrass-based diets from zero-grazing and silage systems

BACKGROUND: Two experiments were conducted to compare the effects of white and red clover on the fatty acid composition of milk fat from cows fed ryegrass-based diets. In experiment 1, fresh ryegrass was mixed with white or red clover (60/40, on a dry matter (DM) basis). Experiment 2 involved similar mixed diets in ensiled form, and one ryegrass-silage diet without the addition of clover. RESULTS: Total DM intake, milk yield and milk fat content were not affected by dietary treatments. Feeding freshly cut white versus red clover supplemented diets resulted in a higher proportion of n-3 fatty acids, especially alpha-linolenic acid, in milk fat. Addition of any clover silage to ryegrass silage increased the proportions of n-3 fatty acids in milk fat, and reduced the proportions of conjugated linoleic acids (CLA), including C18:2 c9t11, and C18:1cis isomers. The n-6/n-3 ratio was elevated compared to the diet not supplemented with clover. CONCLUSION: White clover seemed to be slightly superior to red clover supplementation, but the effects of clover supplementation as such were generally larger than that of clover type. However, a higher concentration of n-3 fatty acids with clover supplementation coincided with a lower concentration of CLA in the milk fat. (C) 2007 Society of Chemical Industry.