title: Manipulation of reproductive seasonality using melatonin implantation in Anglo-Nubian does treated with controlled internal drug release and equine chorionic gonadotropin during the nonbreeding season.
abstract: The objective of this study was to compare the efficiency of hormonal treatments on ovarian activity and reproductive performance in anestrous Anglo-Nubian does during the nonbreeding season (February to May). A total of 48 multiparous does were divided into 2 groups (24 lactating does and 24 dry does). In each group, animals were allocated randomly into 2 equal subgroups (12 does each). In the first subgroup, does received a single 18-mg melatonin implant for 42 d followed by a controlled internal drug release (CIDR) device for 19 d in conjunction with 500 IU of equine chorionic gonadotropin (eCG) i.m. on the day of CIDR device removal. The second subgroup received CIDR combined with eCG in parallel with the first subgroup. Melatonin implantation induced a luteotrophic effect, expressed as an increasing number of corpora lutea, increased serum progesterone concentration, and reduced estradiol concentration. Regardless of treatment, dry does showed greater value of progesterone concentration. With the advancement of day of treatment, number of total follicles, small follicles, and medium follicles tended to increase to the greatest values at the day of CIDR device insertion. Furthermore, at day of mating, the numbers of large follicles reached the greatest value, which was associated with the lowest value of the number of corpora lutea. At day of mating, serum progesterone concentration achieved the lowest value, which increased until d 56 of pregnancy. The estradiol:progesterone ratio showed the opposite trend. The detrimental effect of reproductive seasonality, expressed as cessation of estrus behavior and fertile mating during the nonbreeding season, was successfully alleviated by the CIDR-eCG protocol. Furthermore, melatonin implantation in conjunction with the CIDR-eCG protocol enhanced conception rate and fecundity at d 28 of pregnancy and prolificacy at d 56 of pregnancy compared with does that were not implanted. Interestingly, does that failed to conceive did not come to heat again. In conclusion, the beneficial effect of melatonin implantation in conjunction with the CIDR-eCG protocol on the luteotrophic effect was reflected in the increasing number of corpora lutea, increasing progesterone concentration, and decreasing estradiol concentration. Furthermore, conception rate, prolificacy, and fecundity were improved compared with does that were not implanted during the nonbreeding season.
authors.affiliation: Animal Production Research Institute, Agricultural Research Center, 4 Nadi El-Said, 12311 Dokki, Giza, Egypt.
authors.forename: M Y
authors.initials: MY
authors.lastname: El-Mokadem
authors.affiliation: Animal Production Department, Faculty of Agriculture (El-Shatby), Alexandria University, Alexandria 22545, Egypt.
authors.forename: A N M Nour
authors.initials: ANMN
authors.lastname: El-Din
authors.affiliation: Animal Production Research Institute, Agricultural Research Center, 4 Nadi El-Said, 12311 Dokki, Giza, Egypt.
authors.forename: T A
authors.initials: TA
authors.lastname: Ramadan
authors.affiliation: Animal Production Department, Faculty of Agriculture (El-Shatby), Alexandria University, Alexandria 22545, Egypt.
authors.forename: A M A
authors.initials: AMA
authors.lastname: Rashad
authors.affiliation: Animal Production Department, Faculty of Agriculture (El-Shatby), Alexandria University, Alexandria 22545, Egypt. Electronic address: tahaataha@yahoo.com.
authors.forename: T A
authors.initials: TA
authors.lastname: Taha
authors.affiliation: Animal Production Department, Faculty of Agriculture (El-Shatby), Alexandria University, Alexandria 22545, Egypt.
authors.forename: M A
authors.initials: MA
authors.lastname: Samak
mesh_terms: D000780:Anestrus; D000822:Animal Husbandry / Q000379:methods*; D000818:Animals; D004343:Drug Implants; D065546:Drug Liberation; D004958:Estradiol / Q000097:blood; D004973:Estrus Synchronization; D005260:Female; D005306:Fertilization / Q000187:drug effects* / Q000502:physiology; D006064:Gonadotropins, Equine / Q000008:administration & dosage*; D006736:Horses; D007774:Lactation; D008183:Luteal Phase / Q000187:drug effects / Q000502:physiology; D008550:Melatonin / Q000008:administration & dosage*; D006080:Ovarian Follicle / Q000033:anatomy & histology / Q000187:drug effects; D011247:Pregnancy; D011374:Progesterone / Q000097:blood; D012098:Reproduction / Q000187:drug effects* / Q000502:physiology; D012621:Seasons
chemical_list: D004343:Drug Implants; D006064:Gonadotropins, Equine; D011374:Progesterone; D004958:Estradiol; D008550:Melatonin
keywords: controlled internal drug release–equine chorionic gonadotropin protocol; goat; melatonin; reproductive seasonality