Comparison of a novel Ovsynch program utilising early pregnancy diagnosis as a measure of performance in Australian pasture based dairy herds

Abstract

In recent years the fertility of the dairy cow has been decreasing and there has been some speculation that the current Ovsynch programs on the market have not been used at the optimum time. Ovsynch is an oestrus synchrony program where hormone injections are used to bring cows into oestrus so that fixed time artificial insemination (FTAI) can be used. The original program involves an injection of gonadotropin-releasing hormone (GnRH) on day 0, prostaglandin (PGF2α) on day 7, GnRH on day 9 and FTAI on day 10. Based on studies looking at progesterone levels with the current Ovsynch program, a new program was proposed incorporating a second injection of PGF2α on day 8 to increase the probability of atresia of the corpus luteum (CL). The efficacy of the program will be established through early pregnancy diagnosis. A subset of animals in each group was submitted for progesterone testing on two separate occasions as an indication of whether ovulation occurred at AI.