Stimulation of Estrus and Ovulation by Resynchronization in Kangal Sheep during Early Anestrus
1
Department of Obstetrics and Gynecology, Faculty of Veterinary Medicine, Sivas Cumhuriyet University, Sivas 58140, Türkiye
2
Department of Obstetrics and Gynecology, Faculty of Veterinary Medicine, Selcuk University, Konya 42130, Türkiye
*
Author to whom correspondence should be addressed.
Vet. Sci. 2023, 10(8), 499; https://doi.org/10.3390/vetsci10080499
Submission received: 20 June 2023
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Revised: 24 July 2023
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Accepted: 27 July 2023
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Published: 2 August 2023
(This article belongs to the Special Issue Development of Assisted Reproduction Technologies in Small Ruminants)
Simple Summary
For the last 20 years, it has been aimed to prevent seasonality that limits fertility in sheep. Although numerous sexual stimulations were attempted to induce fertile ovulatory anestrus, desired rates of pregnancy could not be achieved through such one-time stimulations. It has been repeatedly proved that despite estrus being induced and sheep being mated, sheep were turned into deep anestrus if sheep were not conceived. Thus, herein a second chance of pregnancy was given to animals who could not conceive despite the activation of reproductivity. In this context, the method of resynchronization that has successfully been implemented over cows for years was tried for the first time in sheep reproduction following required modifications. The successful adaptation of these existing systematic applications to sheep will enable two consecutive progesterone-supported synchronizations. Thus, while progestative support is provided in the implantation phase to the ewes that conceive at the first stimulation, pregnancies will be increased by providing a second mating for those who do not become pregnant without losing time.
Abstract
A total of 100 Kangal sheep were divided into four groups with the aim of investigating the effectiveness of resynchronization during anestrus for the first time in the literature. The groups were then divided into two further subgroups, namely the resynchronization subgroup group (hCG+resynch) and group (resynch)) and the no resynchronization subgroup (Group (hCG) and group (control)). All the groups started with progesterone-containing sponge insertion on Day 7. The sponge was removed after 7 days (on Day 0), and 600 IU eCG + 131.5 µg PGF2α was injected. The animals in group (hCG+resynch) and group (hCG) received hCG injection at the time of sponge administration. Accordingly, four different groups were established, i.e., resynchronization + hCG administration group (hCG+resynch); n:25), no resynchronization + hCG administration (group (hCG); n:25), resynchronization + no hCG administration (group (resynch); n:25), and no resynchronization + no hCG administration (Group (control); n:25). Estrus rates at the first application in group (hCG+resynch), group (hCG), group (resynch), and group (control) groups were 76%, 88%, 96%, and 76%, respectively, and pregnancy rates were 52%, 64%, 72%, and 60%, respectively; there were no intergroup statistical differences in the two parameters above. It was concluded that resynchronization performed with two consecutive stimulations during anestrus could help save time and provide a pregnancy rate at a level that can provide economic returns.
Keywords:
sheep; estrous stimulation; resynchronization; pregnancy
