Fatty acid profile of milk from dairy cows fed Mexican aster (Cosmos bipinnatus Cav.) silage in small-scale dairy systems in central Mexico

In the search for forage alternatives for the dry season in small-scale dairy systems, spontaneous vegetation such Cosmos bipinnatus Cav., the Mexican aster (cosmos), a weed in the central highlands, can be an option as silage.Cosmos has secondary metabolites that affect rumen fermentation, which may affect the fatty acid profile of milk and the content of beneficial acids.Given the interest of consumers, it is necessary to determine the fatty acid content in milk from cows fed cosmos.The objective was to determine the fatty acid profile of feed and milk from cows fed silage with a high proportion of cosmos.Nine multiparous Holstein cows, grouped in trios, were randomly assigned to treatments in a 33 Latin square design repeated three times.Treatments were 10 kg DM cow -1 d -1 silage containing 40% cosmos (CB40), 60% cosmos (CB60), or 10 kg DM cow -1 d -1 maize (Zea mays L.) silage (MZSL).Each cow also received 4.1 kg DM commercial concentrate.As for silages, maize silage had less content (p < 0.05) of saturated fatty acids (SFA), and higher (p < 0.05) monounsaturated (MUFA) and polyunsaturated (PUFA) fatty acids, compared to CB40 and CB60 silages.However, in the milk profile, the treatment with the highest (p < 0.05) PUFA content was CB60 (mean 3.83 g 100 g -1 ), 8% higher than MZSL; CB60 also had a lower content (p < 0.05) of lauric and myristic fatty acids, detrimental for human health.The atherogenic index for all treatments was indicative of low cardiovascular disease risk.It was concluded that C. bipinnatus silages can be a viable alternative to be used in these systems with a health beneficial fatty acid profile in milk.