Transfer of monoterpenes and sesquiterpenes from forages into milk fat

The transfer of monoterpenes and sesquiterpenes from forages into milk fat was studied in a group of cows fed successively with forages containing high and low amounts of these substances. In a first 24-d period the cows received 11 kg of a cocksfoot hay containing low quantities of monoterpenes and sesquiterpenes. In a second 36-d period, 3 kg of the cocksfoot were replaced by 3 kg of yarrow. a plant rich in terpenoids. In a third 24-d period the cows returned to the cocksfoot-based diet they were fed in the first period. The quantities of monoterpenes and sesquiterpenes desorbed from the milk fat were measured by dynamic headspace - gas chromatography - mass spectrometry. Results showed that the quantities of monoterpenes had increased by the first milking carried out 8 h after ingestion of yarrow, whereas the increase in the quantities of sesquiterpenes was observed only after the third milking, 32 h after the diet change. The maximal quantities of monoterpenes and sesquiterpenes were measured after 4 d of the yarrow-enriched diet, after which the total quantities decreased, despite the constant supply of yarrow. Four days after discontinuing yarrow the amounts of monoterpenes and sesquiterpenes desorbed from the milk fat reverted to those measured during the first period.