GnRH and prostaglandin‐based synchronization protocols as alternatives to progestogen‐based treatments in sheep

Abstract

The study investigated, for cycling sheep, synchronizing protocols simultaneously to the standard "P" protocol using progestogens priming with intravaginal devices and gonadotropin. In November 2014, 90 adult Menz ewes were assigned to either the "P" protocol, "PGF" treatment where oestrus and ovulation were synchronized using two injections of prostaglandin 11 days apart or a "GnRH" treatment where the ewes had their oestrus and ovulation synchronized with GnRH (day 0)-prostaglandin (day 6)-GnRH (day 9) sequence. The ewes were naturally mated at the induced oestrus and the following 36 days. Plasma progesterone revealed that 92% of the ewes were ovulating before synchronization and all, except one, ovulated in response to the applied treatments. All "P" ewes exhibited oestrus during the 96-hr period after the end of the treatments in comparison with only 79.3% and 73.3% for "PGF" and "GnRH" ewes, respectively (p < .05). Onset and duration of oestrus were affected by the hormonal treatment (p < .05); "GnRH" ewes showed oestrus earliest and had the shortest oestrous duration. Lambing rate from mating at the induced oestrus was lower for "P" than for "PGF" ewes (55.6% and 79.3%, respectively; p < .05). The same trait was also lower for "P" than for "PGF" and "GnRH" ewes (70.4%, 89.7% and 86.7%, respectively; p < .05) following the 36-day mating period. Prostaglandin and GnRH analogue-based protocols are promising alternatives for both controlled natural mating and fixed insemination of Menz sheep after the rainy season when most animals are spontaneously cycling.

Effect of different dosages of PG-600 on ovulation and pregnancy rates in ewes during the breeding season

“…However, fecundity rate did not differ in the current study among treatment groups ( Table 1 ). In addition, there was no effect of treatment on birth, litter, or weaning weights of lambs consistent with previous research reported by Rekik et al (2016) .…”

Administration time of misoprostol affects fertility rate in artificially inseminated Kivircik ewes with frozen-thawed ram semen

“…The mean estrus parameters did not differ (P > 0.05) among the groups. In this study the time to estrus onset following the withdrawal of a sponge were 38, 44 and 41 h in the control, Miso11 and Miso6 groups, respectively, which were longer than the 28 h found by Rekik et al (2016) and similar to that found by Zeleke et al (2005) and Zonturlu et al (2011). Estrus duration time was shorter than reported by Ustuner et al (2007) and similar to those reported by Zeleke et al (2005) and Zonturlu et al (2011).…”

Efficiency of CIDR-Based Protocols Including GnRH Instead of eCG for Estrus Synchronization in Sheep

“…In fact, later studies trying to replace eCG with hCG, at least partly if using PG600, showed poorer fertility yields [7,8]. The most promising results have been found when using GnRH to stimulate ovulation [9], although this hormone has been more frequently associated with prostaglandin-based protocols [10,11,12]. It is important to note that GnRH must be applied at least 24–36 h after progestagen removal or luteolysis [13], since its earlier application (e.g., at progestagen removal) causes luteinization of the preovulatory follicle and anovulation [14].…”