Induction of ovulation using repeated doses of sulpiride, a dopamine antagonist, in ewe lambs

This study aimed to test the hypothesis that sulpiride can increase the concentration of circulating gonadotropin that can promote puberty in pre-pubertal ewe lambs. Here, 12 1–3-year-old Merino rams and 60 7–9-month-old Merino sheep were included in the study. The sheep were randomly divided into sulpiride (n = 30) and control (n = 30) groups. The sulpiride group was subcutaneously injected with 0.6 mg/kg sulpiride twice daily (morning and evening) for 9 days. During these 9 days, blood samples were taken from the sheep before drug administration and at 4 h after every drug administration. The number of ovulating animals in the sulpiride group was significantly higher than that in the control group (90% vs. 32%). No oestrous signs were observed in either group during ram release. Further, there were no differences in the levels of mean follicle-stimulating hormone in the two groups based on treatment (p =.2), time (p =.3) or treatment-by-time interaction (p =.3). After sulpiride administration, the luteinizing hormone (LH) levels of the sulpiride group rapidly increased and remained stable for a long time, whereas physiological LH fluctuations in the control group remained unchanged. Within-group changes in terms of LH concentrations were significant for both groups (p <.001), whereas LH pulse frequency was significantly different between the sulpiride group (p =.03). Therefore, it is concluded that sulpiride can be used as a non-steroidal alternative to stimulate pre-pubertal ewe lambs and sheep during anoestrus. © 2022 Wiley-VCH GmbH.