Incidence of Premature Luteal Regression in Ewes Superovulated with a Single Injection of Follicle-Stimulating Hormone Combined with Equine Chorionic Gonadotropin.

Abstract

Abstract. The incidence of premature corpora lutea (CL) regression was investigated in three different breeds (Merino x polled Dorset: MD, Suffolk: S, and South-Down: SD), parous and nonparous ewes (a total of 46 ewes) treated for superovulation during and out of the breeding season. Superovulation was induced with a single injection of 20 mg porcine follicle-stimulating hormone (pFSH) 2 days and 500 IU equine chorionic gonadotropin (eCG) 1 day, respectively before the removal of synthetic progestogen (40 mg FGA) vaginal sponges inserted for 12 days. All ewes were inseminated into the uterus with fresh-diluted or frozen-thawed semen by laparoscope, and a number of newly formed and regressed CL were recorded. Breed difference significantly (P<0.005) affected the incidence of premature regressed CL; S (6.3%, n=16) ewes were less in the proportion of the incidence of regressed CL than MD (37.5%, n=16: P<0.05) and SD (71.4%, N=14, P<0.01) ewes. The use of non-parous ewes and treatment during autumn tended to result in higher rates of incidence of premature CL regression than the use of parous ewes and treatment during spring. These results indicate that the incidene of premature CL regression in superovulated ewes was influenced by not only season and parity but also by breed of ewes used for superovulation treatment.

Effect of Dosage of Equine Chorionic Gonadotropin Combined with a Single Injection of Porcine Follicle-Stimulating Hormone for Superovulation Treatment in Ewes.

“…Our previous study [7] also showed that SD ewes showed a higher rate of corpous luteum (CL) regression than Sf and MD ewes treated with a 20 mg pFSH injection combined with 500 IU eCG. There is no report on superovulatory response in SD ewes compared with other breeds of ewes.…”

“…However, the ovarian response was greater in Merino ewes carrying Booroola gene than those with non-carriers [28]. This suggests that breed differences significantly affect the incidence of premature luteal regression [7]. It has been considered that endogenous PGF 2α and/or oxytocin arising from the response to prolonged stimulation by elevated circulating levels of E2 may be causative factors in premature luteal regression [26].…”

“…It was demonstrated by our previous studies that superovulation can be induced with a single injection of 20 mg porcine FSH (pFSH) combined with 500 IU eCG in Suffolk (Sf) and Merino × polled Dorset (MD) ewes [5,6]. Superovulatory responses in treated ewes has varied with differences of season [1], administration method [4] and breed [7]. Premature luteal regression before embryo recovery is one of the major drawbacks of superovulatory treatment, and has been reported in superovulated cattle [8,9], deer [10] and goats [11,12].…”

“…The phenomenon of premature luteal regression is accompanied by a low ova/embryo recovery rate and a high percentage of poor quality embryos recovered [13]. In three different breeds of ewes (Sf, MD and South-Down : SD), Fukui et al [7] found that SD ewes showed the higher rate (70%) of premature CL regression than Sf or MD ewes and concluded that not only parity and season, but also breed of ewe affected the incidence of premature CL regression in superovulated ewes.…”

Técnicas de superovulação em ruminantes

“…O fenômeno parece estar associado a elevadas concentrações plasmáticas de estrógenos durante a fase lútea inicial e, em conseqüência, nota-se um decréscimo na taxa de recuperação de embriões. Em ovelhas superovuladas, a regressão lútea precoce pode variar de 6,0% a 75,0% (FUKUI et al, 1998;LOPES Jr et al, 2006). sendo aplicado aplicado apenas uma vez ao dia, diminuindo assim os custos com este tratamento (SALLES et al, 1998).…”