Efficacy of Various Synchronization Protocols on the Estrus Behavior, Lambing Rate and Prolificacy in Rahmani Egyptian Ewes During the Non-Breeding Season

Abstract

Although various progestagens are often used to induce and synchronize estrus and ovulation in small ruminants, concerns regarding residues are the impetus to develop alternative approaches, including reduced doses of progestagens. Therefore, this study investigated the effects of various estrus synchronization protocols on fertility of Rahmani ewes during the non-breeding season. In June, 82 ewes were randomly assigned to five groups and each group received 1 of 5 treatments: (1) The ewes (n = 10) intramuscularly (IM) injected with 20 mg progesterone (P4) acetate day after day for 12 days and equine Chorionic Gonadotropin (eCG) on day 12, (2) Two doses of prostaglandin (PG) F 2" 9 days apart (n = 10) and eCG on day 9, (3) Ovulation synchronization (OVS, n = 10) with a gonadotropin Releasing Hormone (GnRH, day 0), PGF 2" (day 5) and GnRH 48 h later, (4) Whole (20 mg, n = 20), or halved (10 mg, n = 22) Progesterone Releasing Intravaginal Device (PRID) for 6, 8 and 14 days; PGF 2" a day prior to PRID removal and eCG at PRID removal and (5) Untreated-ewes (Control, n = 10). Blood samples were taken for serum P4 assay. There were significant differences (p<0.05) among treatments for estrus rate, onset of estrus, pregnancy and lambing rates as well as prolificacy. The highest (100%) estrus rate recorded in whole-PRID for 6 days and halved-PRID for 8 days, while the rapid onset (24 h) of estrus was in PGF 2" . Pregnancy and lambing rates were greater (p<0.05) in PGF 2" and halved-PRID for 8 days. The highest prolificacy (1.75) was recorded with whole-PRID for 6 days whereas; the lowest (1.0) was recorded with PGF 2" and halved-PRID for 8 and 14 days. Serum P4 concentrations were not different among all PRID protocols on 4, 7 and 13 days. In conclusion, all synchronization protocols except OVS had a positive effect on ewe fertility during the non-breeding season.