EFFECT OF GnRH INJECTION ON FERTILITY PARAMETERS IN MORKARAMAN SHEEP IN THE BREEDING SEASON

Abstract

This study aimed to investigate the effect of GnRH injection on the first synchronization day on lambing performance and fertility in a short-term progesterone-based synchronization protocol in Morkaraman sheep during the breeding season. The study material consisted of 76 Morkaraman sheep in the breeding season. Clinically healthy and non-lactating ewes with an average age of 2-3 years, a BCS of 3.16±0.04, a weight of 63.98±0.79 kg, and five healthy fertile rams of adult age were included in the study. The rams were separated from the herd one month before the study started. The sheep were divided into two groups without intravaginal sponge placement. Intravaginal sponges (20 mg flugestone acetate, Chronogest®, France) were placed in all sheep to remain in the vagina for 6 days, and 1.5 mL PGF2α (5 mg, Dinoprost, Enzaprost®, France) was injected intramuscularly 1 day before (day 5) and on the day the sponge (day 6) was removed. In the first group of sheep (n=39), 2 mL of GnRH (0.004 mg buserelin, Receptal®, Germany) was injected intramuscularly immediately after the sponge was placed in the vagina (Day 0). Unlike the first group, sheep in Group II (n=37) were injected with physiological saline (2 mL, i.m.) after the sponge was placed intravaginally. Immediately after the sponge was removed (day 6), all sheep were injected with 600 IU of eCG (Chrono-gest/PMSG, Germany), and the rams joined the herd. After mating the ram, the oestrus was monitored for 5 days. Pregnancy examinations were performed transrectally on the 30th day following mating. It was determined that the vaginal sponge was lost in two sheep each in Groups I and II, and these sheep were excluded from the study. It was determined that 54.05% of the ewes in Group I and 48.57% of the ewes in Group II were pregnant. Lambing was observed in all pregnant ewes. The multiple pregnancy rate was found to be less in Group I (45%) than in Group II (52.94%). A total of 32 lambs were obtained in Group I, and 26 lambs were obtained in Group II. Average lamb weights were found to be similar in both groups. As a result, GnRH injection combined with intravaginal sponge application may contribute to fertility success by numerically increasing the rate of estrus, pregnancy, and litter size.

Keywords

• breeding season
• fertility
• GnRH
• sheep
• synchronization