At 11-13 days after insemination, 1028 dairy cows on 19 farms
were treated with an intramuscular injection of 10 ?g of the GnRH
analogue Buserelin. Reproductive performance was compared to 1022
control cows receiving a placebo. Cows treated with the GnRH analogue
had a reduced number of short interoestrus intervals compared to
control cows but there were no significant differences in pregnancy
rates to the insemination preceding or following treatment. Calving-to
-conception intervals and percent pregnant by the end of mating were
also unaffected. There were no differences between treatments in herds
of high, average or low pregnancy rates, within different age groups or
within different calving to first service intervals.
The evidence here suggests that the use of 10 ?g of the GnRH
analogue, Buserelin, 11-13 days post-insemination cannot be
recommended as a method of improving reproductive performance in
dairy herds.