The effect of prostaglandin and gonadotrophins (GnRH and hCG) injection combined with the ram effect on progesterone concentrations and reproductive performance of Karakul ewes during the non‐breeding season

Abstract

The effect of prostaglandin and gonadotrophins (GnRH and hCG) combined with the ram effect on the progesterone (P4) concentrations and reproductive performance of Karakul ewes was investigated during non‐breeding season. Ewes (n = 93) received a male effect and were divided into two treatment groups including GnRH ‐ hCG (hCG, n = 32), GnRH ‐ GnRH (GnRH, n = 30) and a control (n = 31) group. This study was carried out from April (hormonal injection) to October (lambing). The first doses of GnRH (4.2 μg, Buserelin) were injected at the beginning of the study in treatment groups. These ewes were treated with hCG (250 IU) or the second GnRH dose five days later. All animals received two injections (ten days apart) of 150 μg PGF2α five days after the hCG or the second GnRH injection. Mating was initiated two days after the second prostaglandin injection and lasted for 34 days. Blood samples were collected by jugular venipuncture on days −10, −5, 0 (first PGF2α injection), 17 and 30 during the study. Pregnancy diagnosis was performed through transabdominal ultrasonography on day 40 after the removing of ram. Conception rate was 93.8, 90 and 87.1% in the hCG, GnRH and control groups, respectively. Lambing rate tended to increase in the hCG group compared with the control group (87.1 versus 58.1%; p < .1). There was no significant difference in P4 concentrations among studied groups in identical sampling times (p > .05). In conclusion, the administration of prostaglandin and hCG in combination with the ram effect tended to decrease lambing period. In other words this protocol tended to increase lambing rate at the first cycle. Treatment with hCG or GnRH did not increase serum P4 concentrations of treated Karakul ewes during the non‐breeding season.

The effect of human menopausal gonadotropin and equine chorionic gonadotropin on the reproductive performance of treated ewes with short‐term progesterone injections and sponge during the non‐breeding season

“…Follicular growth and subsequently oestrous signs in hMG‐treated ewe may be due to its FSH‐ and LH‐like actions (Hussein et al., 2021). In the present study, some control ewes got pregnant but the number was significantly lower than that of the treatment groups because the ram effect may be associated with ovulation in some ewes during the non‐breeding season (Ayaseh et al., 2021; Dehkordi et al., 2022). In addition, the ram effect is able to induce silent ovulation or short cycles in control group.…”

Respuesta reproductiva de ovejas multíparas postparto y nulíparas a inyecciones de GnRH y prostaglandina F2α

“…However, the formation of corpus luteum in response to single or multiples injections of GnRH was not reported by Jordan and colleagues in seasonal anestrus ewes (Jordan et al, 2009). This is because follicle atresia might also occur if responsive follicles are not present when GnRH is given to animals (Twagiramungu et al, 1995), which complete avoids the possibility of corpus luteum formation (Ayaseh et al, 2021).…”

Effects of exogenous GnRH administration on lambing performance of oestrus‐synchronized Kazak ewes during the breeding season

“…In oestrus‐synchronized Awassi ewes after short‐term progestagen administration, a dose of 50 μg GnRH (Gonodarelin diacetate) given 48 h after removal of the progestagen pessary decreased the pregnancy rate to 37.9% compared with 55.2% in its own control group (Kutlu & Dinç, 2021). Some other studies, in which injection of a single dose of GnRH (24 h ‐ 48 h after removal of the progestagen pessary/on the day of oestrus) was performed during the breeding season, reported varying degrees of positive responses from 4% to 73.2% in pregnancy rate (Kutlu & Dinç, 2021; Sirjani et al, 2012; Walker et al, 1989), while some others have reported no changes (Ayaseh et al, 2021; Cavalcanti et al, 2012; Olivera‐Muzante et al, 2011; Türk et al, 2008) or decrease in pregnancy rate (Olivera‐Muzante et al, 2013). Moreover, Biehl et al (2017) reported that the use of GnRH was efficient to increase the pregnancy rate in Santa Ines ewes undergoing the fixed time artificial insemination procedure, and the best protocol to GnRH administration was at the time of insemination because only three managements were required.…”

“…Although GnRH is already widely used in ovine fixed time artificial insemination programmes (Hameed et al, 2021), the effects of GnRH on pregnancy rates are controversial (Menchaca & Rubianes, 2004). Some studies reported that a single dose of GnRH given 24 to 48 h after pessary removal increased the pregnancy rate (Biehl et al, 2017; Kutlu & Dinç, 2021), while some others have reported no changes (Ayaseh et al, 2021; Cavalcanti et al, 2012; Olivera‐Muzante et al, 2011; Reyna et al, 2007; Türk et al, 2008) or even decreased the pregnancy rate (Martemucci & D'Alessandro, 2011; Olivera‐Muzante et al, 2013; Walker et al, 1989).…”