Induction of fertile estrus without the use of steroid hormones in seasonally anestrous Suffolk ewes

Abstract

ObjectiveTo evaluate the efficacy of treatments based on gonadotrophin-releasing hormone (GnRH), GnRH-prostaglandin F2α (PGF2α), and/or intense exposure to novel rams to induce fertile estrus without the use of steroid hormones in seasonally anestrous Suffolk ewes.MethodsIn the first experiment, ewes were treated with one injection of GnRH, two injections of GnRH administered 7 days apart, or a sequence of GnRH-PGF2α-GnRH (GPG). In the second experiment anestrous ewes were exposed, for 36 days starting on the day of weaning, to groups of four rams of three different breeds that were alternated every day. Besides exposure to the male effect (ME), the ewes were injected with saline solution (ME group, n = 20), with GnRH (ME-GnRH group, n = 20) or with a sequence of GnRH-PGF2α-GnRH (ME-GPG group, n = 20). The rams used for male-effect were fitted with aprons to prevent mating, and ewes detected in estrus were bred to selected fertile rams. Ovarian activity was monitored by progesterone determinations in both experiments.ResultsIn the first experiment sustained induction of ovarian activity was not achieved and no ewe was detected in estrus. In the second experiment induction of sustained ovarian activity was achieved in all groups. Most of the ewes were detected in estrus, 76.7% of the ewes were mated during a 36-d breeding period and 71.7% of all the ewes became pregnant during that period. No significant differences between groups were found for any of these variables. However, estrus detection efficiency was higher in the ME-GnRH group than in the ME group (p<0.05).ConclusionAn intense male-effect, that included the continuous presence and frequent alternation of several rams of different breeds, was sufficient to induce ovarian activity and fertile estrus in Suffolk ewes during the period of deep anestrus without the use of hormones, although addition of GnRH improved the efficiency of estrus detection.

Estrous synchronization in cattle, sheep and goat

“…Using Prostaglandin F2alpha: Due to the absence of luteal tissue during anestrous, PGF2alpha alone cannot induce estrous. (Miguel-Cruz et al 2019). However, giving out-of-season ewes two PGF2alpha injections (D-Cloprostenol; 0.15 mg; 10 days apart), together with GnRH (4.2 mg buserelin) before the first PGF2alpha treatment, led to a greater lambing rate (Mirzaei et al 2017).…”

The Effect of the Different Artificial Insemination Time Periods on the Pregnancy Rate of Sapudi Ewes

“…This situation can be affected by many factors, including the quality of the frozen semen which experiences a quality decrease after thawing, incorrect implementation of artificial insemination, and incorrect estrus detection which results in a fertilization failure (Abebe and Alemayehu, 2021). The estrus period detection is highly complicated to perform, which results in difficulties in determining the ovulation period (Miguel-Cruz et al, 2019). The length of ewes' estrus period is around 24-36 hours, and the sheep's ovulation period begins approximately 24-30 hours from the beginning of the estrus time (Miguel-Cruz et al, 2019).…”

“…The estrus period detection is highly complicated to perform, which results in difficulties in determining the ovulation period (Miguel-Cruz et al, 2019). The length of ewes' estrus period is around 24-36 hours, and the sheep's ovulation period begins approximately 24-30 hours from the beginning of the estrus time (Miguel-Cruz et al, 2019). Determining the ovulation period is considered important for an exact time for artificial insemination (Ramadhani, 2016).…”

“…As a result, livestock can be inseminated at the same time. The estrus synchronization commonly is achieved using prostaglandin F2α or PGF 2α hormone (Mirshamsollahi, 2016;Miguel-Cruz et al, 2019). The hormone acts by lysing the corpus luteum, which leads to a decreased level of the progesterone hormone (Ferrag et al, 2017).…”

Development and evaluation of an injectable slow‐release progesterone formulation for estrus synchronization in ewes out of the breeding season

“…Gonadotropic hormones such as FSH and eCG (equine chorionic gonadotropin) used alone are not very effective in inducing estrus in small ruminants especially during non-breeding season. Similarly, prostaglandin treatment is limited to the breeding season and PGF2α alone will not induce estrus during non-breeding season (Miguel-Cruz et al, 2019).…”