title: Effect of GnRH treatment on ovarian activity and reproductive performance of low-prolific Rahmani ewes.
abstract: This study was designed to evaluate the effect of GnRH treatment during different times of the reproductive cycle on ovarian activity, progesterone (P4) concentration, and subsequent fertility of low-prolific, subtropical, Rahmani ewes during breeding season. Forty-five ewes were synchronized for estrus using a double injection of 0.5 mL of PGF2α agonist (125-μg cloprostenol), 11 days apart. Ewes showing estrus (Day 0) were treated with 1 mL of GnRH agonist (4-μg buserelin) on the day of estrus (GnRH0, n = 12) or 7 days post-mating (GnRH7, n = 10) or on both days (GnRH0+7, n = 11) or not (control, n = 12). Ovarian response to the treatment and diagnosis of pregnancy were ultrasonographically monitored. Also, serum P4 concentration was determined weekly throughout 28 days post-mating. Results showed that neither total number of follicles nor their populations were changed on Day 0 or 7 days post-mating by the GnRH treatment. GnRH treatment on Day 0 or Day 7 post-mating or both days did not enhance ovulation rate compared with the control. The mean numbers of accessory CL increased (P < 0.05) in the GnRH7 group than those in the control and GnRH0 groups, whereas it was intermediate in the GnRH0+7 group. The greatest (P < 0.05) overall mean of serum P4 concentration was for the GnRH7 and GnRH0+7 groups, followed by the GnRH0 and control groups. Serum P4 concentration increased (P < 0.05) on Day 14 post-mating and continued higher (P < 0.05) until Day 28 post-mating in the GnRH7 and GnRH0+7 groups compared with the control. Regardless of the time of GnRH administration, GnRH treatment reduced (P < 0.05) pregnancy loss from Day 40 post-mating to parturition and tended to enhance (P < 0.20) lambing rate compared with the control. In conclusion, a single dose of GnRH at the time of estrus or 7 days post-mating could be used as an effective protocol to decrease pregnancy loss from Day 40 after mating to parturition in low-prolific Rahmani ewes.
authors.affiliation: Animal Production Department, Faculty of Agriculture (El-Shatby), Alexandria University, Alexandria, Egypt. Electronic address: hashemnesreen@yahoo.com.
authors.forename: N M
authors.initials: NM
authors.lastname: Hashem
authors.affiliation: Animal Production Department, Faculty of Agriculture (El-Shatby), Alexandria University, Alexandria, Egypt.
authors.forename: K M
authors.initials: KM
authors.lastname: El-Azrak
authors.affiliation: Animal Production Department, Faculty of Agriculture (El-Shatby), Alexandria University, Alexandria, Egypt.
authors.forename: A N M
authors.initials: AN
authors.lastname: Nour El-Din
authors.affiliation: Animal Production Department, Faculty of Agriculture (El-Shatby), Alexandria University, Alexandria, Egypt.
authors.forename: T A
authors.initials: TA
authors.lastname: Taha
authors.affiliation: Animal Production Department, Faculty of Agriculture (El-Shatby), Alexandria University, Alexandria, Egypt.
authors.forename: M H
authors.initials: MH
authors.lastname: Salem
mesh_terms: D000818:Animals; D001947:Breeding; D030762:Estrous Cycle / Q000187:drug effects; D004973:Estrus Synchronization; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage*; D006080:Ovarian Follicle / Q000000981:diagnostic imaging / Q000187:drug effects / Q000502:physiology; D010053:Ovary / Q000000981:diagnostic imaging / Q000187:drug effects* / Q000502:physiology*; D011247:Pregnancy; D011374:Progesterone / Q000097:blood; D012098:Reproduction / Q000187:drug effects* / Q000502:physiology; D012756:Sheep / Q000502:physiology*; D014463:Ultrasonography
chemical_list: D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone
keywords: Embryonic mortality; GnRH; Ovulation rate; Progesterone; Rahmani ewe