Pre-ovulatory follicles and ipsilateral ovarian stroma are cooler than non-dominant antral follicles and stroma on the contralateral ovary of the mare.
Mares show cooling in pre-ovulatory follicles compared to non-dominant follicles, which may be important for understanding fertility.
Where it sits
this study against the rest of the deslorelin corpusSummary and findings
This study measured the temperature of pre-ovulatory follicles (POFs) in mares and compared it with other ovarian regions. Deslorelin was administered when an ovarian follicle ≥38 mm was present. The POF was found to be cooler than the non-dominant follicle (NDF) on the contralateral ovary.
Abstract
Reports in several species have demonstrated that pre-ovulatory follicles (POFs) are cooler than neighbouring ovarian tissue, with cooling important for fertility. This study measured the temperature of POFs and compared it with other regions of the ovary, cervix, and rectum to determine if POF cooling occurs in mares. Fourteen oestrous cycles in 11 mares were monitored, and when an ovarian follicle ≥38 mm was present, deslorelin was given. Thirty hours later, rectal and cervical temperature measurements were taken. Mares were sedated and ovarian temperature measurements taken using a thermocouple probe in a 12G needle within a transvaginal probe. Measurements were made in the POF and a non-dominant follicle (NDF) on the contralateral ovary. In eight mares the temperature of the stroma in each ovary was also recorded. The data were analysed using a paired t-test. The POF was cooler than the contralateral NDF (p < 0.001) with a mean difference of 0.30 ± 0.17°C (n = 14). However, the stroma ipsilateral to the POF was cooler than the POF (p = 0.003; n = 8), whereas a NDF and stromal tissue within that ovary were statistically equivalent in temperature (p = 0.18; n = 8). The mare shows POF cooling, but unlike other species, the whole ovary is involved. This variation in cooling between ovarian compartments compared to other species could be related to the unusual structure of the equine ovary. Being cognisant of temperature changes within the ovaries around the time of ovulation in the mare could help our understanding of oocyte maturation and competence in vivo and in vitro.
Background
This paper addresses the temperature dynamics of pre-ovulatory follicles (POFs) in mares, a topic previously explored in other species. Prior studies have indicated that POFs are cooler than surrounding ovarian tissue, which is thought to be important for fertility. Understanding these temperature differences in mares could provide insights into oocyte maturation and fertility.
Methods
The study monitored fourteen oestrous cycles in 11 mares. Deslorelin was administered when an ovarian follicle ≥38 mm was present. Rectal and cervical temperature measurements were taken 30 hours post-administration, and ovarian temperatures were measured using a thermocouple probe in a 12G needle within a transvaginal probe. The primary outcome was the temperature comparison between POFs and non-dominant follicles.
Results
The primary endpoint showed that the POF was cooler than the contralateral non-dominant follicle (p < 0.001) with a mean difference of 0.30 ± 0.17°C (n=14). Additionally, the stroma ipsilateral to the POF was cooler than the POF (p = 0.003; n=8). The temperature of the NDF and its stromal tissue was not significantly different (p = 0.18; n=8).
Interpretation
These findings suggest a unique cooling mechanism in equine ovaries that differs from other species. While the statistical significance of the temperature differences is clear, the clinical relevance of a 0.30°C difference may be limited. Confounding factors include the small sample size and the potential impact of sedation on temperature readings.
Key findings
- POF was cooler than contralateral NDF (p < 0.001) with a mean difference of 0.30 ± 0.17°C (n=14)
- Stroma ipsilateral to POF was cooler than POF (p = 0.003; n=8)
- NDF and stromal tissue within that ovary were statistically equivalent in temperature (p = 0.18; n=8)
Limitations
- small sample size of 11 mares
- sedation during measurements could affect results
- single-site study limits generalizability
- no long-term follow-up data reported