Investigations of the efficacy of oral tyrosine applications in the postpartum period on the reproductive performance of dairy cows

298 dairy cows from 6 farms were included to test the efficacy of a single oral dose of 50 or 100 g L-tyrosine at day 8,12 or 21 postpartum in a double blind trial to assess its possible effect on the frequency of anoestrus, cystic ovaries, and reproductive parameters. It was concluded that there was a clear effect of tyrosine on the induction of follicle growth, the clinical signs of oestrus and the number of corpora lutea. The incidence of cystic ovaries was reduced. The results therefore suggest the possible practical use of this treatment, but more specific investigations are necessary.