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

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. Vpliv aplikacije GnRH na parametre plodnosti pri ovcah pasme morkaraman v paritveni sezoni Izvleček: Namen raziskave je bil preučiti učinek odmerka GnRH prvi dan sinhronizacije na uspešnost jagnjitev in plodnost pri kratkoročnem protokolu sinhronizacije na osnovi progesterona pri ovcah pasme morkaraman med paritveno sezono. Raziskava je bila izvedena na 76 ovcah te pasme v paritveni sezoni. V raziskavo so bile vključene klinično zdrave ovce brez laktacije povprečne starosti 2–3 leta z oceno telesne kondicije 3,16 ± 0,04 in telesno maso 63,98 ± 0,79 kg ter pet zdravih odraslih plodnih ovnov. Ovni so bili ločeni od črede en mesec pred začetkom raziskave. Ovce so bile razdeljene v dve skupini pred vstavitvijo intravaginalnih gobic. Vsem ovcam so bile vstavljene intravaginalne gobice (20 mg flugeston acetata, Chronogest®, Francija), ki so ostale v nožnici 6 dni, en dan pred odstranitvijo gobice (5. dan) in na dan odstranitve (6. dan) so intramuskularno aplicirali 1,5 mL PGF2α (5 mg, Dinoprost, Enzaprost®, Francija). Prvi skupini ovc (n = 39) so intramuskularno aplicirali 2 mL GnRH (0,004 mg buserelina, Receptal®, Nemčija) takoj po vstavitvi gobice v nožnico (dan 0). Za razliko od prve skupine so ovcam v drugi skupini (n = 37) po intravaginalni vstavitvi gobice aplicirali fiziološko raztopino (2 mL, i. m.). Takoj po odstranitvi gobice (6. dan) so vsem ovcam aplicirali 600 IU eCG (Chrono-gest/PMSG, Nemčija), ovni pa so se pridružili čredi. Po pripustu ovna so estrus spremljali 5 dni. Preglede brejosti so opravili transrektalno 30. dan po parjenju. Ugotovljeno je bilo, da sta po dve ovci iz prve in druge skupine izgubili vaginalno gobico, zato sta bili izključeni iz raziskave. Brejost je bila ugotovljena pri 54,05 odstotka ovc iz prve skupine in 48,57 odstotka ovc iz druge skupine. Vse breje ovce so jagnjile. Ugotovljeno je bilo, da je bila stopnja večplodnih brejosti v prvi skupini (45-odstotna) manjša kot v drugi skupini (52,94-odstotna). V prvi skupini je bilo skupno 32 jagnjet, v drugi skupini pa 26. Povprečna teža jagnjet je bila v obeh skupinah podobna. Odmerek GnRH v kombinaciji z uporabo intravaginalne gobice lahko prispeva k uspešnosti plodnosti, saj številčno poveča stopnjo estrusa, brejosti in velikosti mladičev. Ključne besede: paritvena sezona; plodnost; GnRH; ovce; sinhronizacija