Effects of different protocols for estrus synchronization in ewes on vaginal pH, estrus time and reproductive performance and change in vaginal electrical resistance values

Abstract

This study examined the effects of different intravaginal apparatus types used for estrus cycle management in ewes, as well as the timing of their insertion and withdrawal on vaginal pH and reproductive performance. Additionally, this study aimed to investigate changes in VER levels during estrus and anestrus in Kivircik ewes. A total of 90 Kivircik ewes in the estrus period were synchronized using fluorogestone acetate (FGA) sponges and controlled internal drug release (CIDR) protocols ranging from short (5 days) to medium (9 days) up to long-term (13 days). Additionally, 350 IU of equine chorionic gonadotropin (eCG) were injected intramuscularly when the FGA and CIDR were withdrawn from all the groups. Vaginal pH samples were taken on the days of vaginal apparatus removal (days 5, 9 and 13), as well as the first day of estrus and anestrus. Vaginal pH increased more markedly in ewes treated with FGA and CIDR when compared to those in anestrus, especially in the medium and long-term treated ewes, which had a pH value around 7.7. Both medium and long-term protocols had a high success rate for estrus occurrence, with all the tested ewes entering estrus. However, ewes in the FGA medium-term group presented the earliest estrus at 32.8 hours. Although statistically non-significant, the CIDR protocol resulted in numerically higher results for multiple birth rate, fecundity and litter size. The electrical resistance of vaginal mucus was measured during anestrus and immediately after estrus detection. VER values were recorded to be lower during estrus. VER values between 200 and 300 Omega might be indicative of estrus in ewes.