Most evidence to date suggests that endogenous synthesis
is the major source of cis-9,trans-11 in milk fat and ruminal outflow is limited and largely independent of dietary 18 : 2n-6 supply. Four
lactating cows fitted with a rumen cannula were used in a 4 £ 4 Latin square with 14 d experimental periods to examine the effects of sunflower-
seed oil (SFO) as a source of 18 : 2n-6 on ruminal lipid metabolism. Cows were offered grass silage-based diets supplemented with 0,
250, 500 or 750 g SFO/d.