Restoration of LH output and 17 beta-oestradiol responsiveness in acutely ovariectomised Holstein dairy cows pre-treated with a GnRH agonist (deslorelin) for 10 days

摘要

The objectives of the study were firstly to identify the role of the ovary in maintaining plasma luteinising hormone (LH) concentrations in cows treated with an implant of a potent GnRH agonist (deslorelin), and secondly to characterise the changes in LH following ovariectomy (OVX) in the same animals. Oestrus was synchronised in mature Holstein dairy cows and deslorelin implants were inserted 17 days later into two-third of the cows. A further 10 days later (day 0) all cows had bilateral OVX performed. A control group (CON; n = 4) received no treatment and had blood samples collected at 15-min intervals for 8 h on the day prior to OVX (day -1) and similarly on days 4 and 10. One group (DES_IN; n = 4) had implants in place for the duration of the study while another group had implants removed (DES_OUT; n = 4) at the time of OVX. DES_IN cows were sampled hourly at each sampling session (days -1, +4 and + 10), whereas DES_OUT cows were sampled similarly to CON except on day-1 when hourly samples were collected.