Milk from cows grazing on cool-season pastures provides an enhanced profile of bioactive fatty acids compared to those grazed on a monoculture of pearl millet

•Evaluated effect of millet vs. pasture on milk production and bioactive fatty acids.•Milk production, milk fat and protein yield did not differ between grazing regimes.•CLA were increased in a serving of whole milk when cows grazed cool-season pasture.•Milk from cows grazed on pasture had a 2-fold greater n-3 fatty acid content. The demand for dairy products from grass-fed cows is driven, in part, by their more desirable fatty acid (FA) profile, containing more n-3 FA and conjugated linoleic acids (CLA) than conventionally produced dairy products. This study investigated the effects of pearl millet (PM) vs. cool-season pasture (CSP) on animal performance and milk FA in a grazing system. Eight Holstein dairy cows were used in a repeated measures design with four-week periods. Forage type had no effect on animal performance (estimated dry matter intake, milk production, fat, or protein). The contents of CLA and n-3 FA in a serving of whole milk (3.25% fat) increased when cows grazed CSP compared to PM. A serving of whole milk from cows grazing PM had a higher content of saturated FA and branched-chain FA. In conclusion, the contents of various bioactive FA were higher in milk fat of cows grazing a CSP compared to PM.