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 hig h and low amounts of these substances. In a first 24-d period the cows rece ived 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 replac ed by 3 kg of yarrow. a plant rich in terpenoids. In a third 24-d period th e cows returned to the cocksfoot-based diet they were fed in the first peri od. The quantities of monoterpenes and sesquiterpenes desorbed from the mil k fat were measured by dynamic headspace - gas chromatography - mass spectr ometry. Results showed that the quantities of monoterpenes had increased by the first milking carried out 8 h after ingestion of yarrow, whereas the i ncrease in the quantities of sesquiterpenes was observed only after the thi rd milking, 32 h after the diet change. The maximal quantities of monoterpe nes 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 a nd sesquiterpenes desorbed from the milk fat reverted to those measured dur ing the first period.