Effect of repeated low doses of gonadotropin-releasing hormone on the secretion of luteinizing hormone and follicle-stimulating hormone, and ovarian function in dairy cows suffering from anovulation type I

The aim of the study was to evaluate the effect of repeated low doses of gonadotropin-releasing hormone (GnRH) agonist buserelin once a day for 5 days on follicle-stimulating hormone (FSH) and luteinizing hormone (LH) release, and ovarian function in dairy cows with anovulation type I. The study was conducted on 10 anovulatory Polish Holstein-Friesian cows. Cows in Group 1 (n = 5) received 4 µg of buserelin intramuscularly. once a day for 5 days. Control cows from Group 2 (n = 5) received saline. Concentrations of progesterone, FSH, and LH in the blood were analysed using radioimmunoassay (RIA). Ovarian structures were monitored weekly after the end of treatment by ultrasound for 4 weeks. Injections of buserelin increased FSH and LH concentrations. Release of FSH and LH was largely variable, but there was significant (P < 0.001) interaction between time and treatment during all treatment days. The number of follicles in the treatment group was significantly greater (P = 0.029) than in the control group on day 5, the diameter of follicles on day 12 was also larger (P < 0.01) in treated than in control cows. Ovulation occurred in 4 of the 5 treated cows, but only in 1 of the control cows in the 40 days after treatment. In conclusion, repeated low doses of GnRH analogue buserelin once a day for 5 days may increase the concentration of FSH and LH in dairy cows with anovulation type I. •Repeated low doses of GnRH increased FSH and LH concentrations in anovulatory cows.•The number and diameter of follicles increased after repeated low doses of GnRH.•Low dose of GnRH can be considered as a treatment method in anovulatory cows.