School of Agriculture, Food and Ecosystem Sciences - Theses

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Effect of GnRH and production levels on reproduction in dairy cattle

Abhayaratne, Damayanthi ( 1990)

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.