High ambient temperature and humidity associated with early embryonic loss after embryo transfer in mares.

The research investigates the impact of increased ambient temperature and humidity on early embryonic loss (EEL) in mares after an embryo transfer. Higher temperature-humidity index (THI) between the 7th and 14th day of gestation was found to increase the odds of EEL.

Study Overview

• This study attempts to understand the influence of the climatic conditions on reproductive outcome, specifically on EEL in mares post embryo transfer, given the increasing rates of ambient temperatures. The focus is on two parameters – THI on the day of transfer (Day 7) and mean THI between Day 7 and Day 14.
• The subjects of the study were recipient mares at a breeding facility in Victoria, Australia. Records of 834 embryo transfers were reviewed for this research.
• The condition of EEL was identified as a negative ultrasound test on the 14th day post embryo transfer which occurred on the 7th day.

Method and Findings

• A multivariable logistic regression was used to analyze the association between THI and EEL. This approach helped control potential confounding factors such as embryo age and quality, mare quality and embryo transfer quality.
• The results showed that an increase in maximum THI on the day of transfer by five units resulted in an 18% increase in the chances of EEL. Also, a similar rise in mean THI between the 7th and 14th day increased EEL odds by 25%. Out of all the embryo transfers, 21% were observed to have EEL.
• Although the study was conducted on a concrete population (mares at a certain equine breeding facility), the researchers suggest that similar effects could be possible in a broader context. Hence, further study is needed to confirm this across a wider population and to identify any potential preventive measures that could be taken during heatwaves.

Significance of the Research

• The research holds importance because the impacts of rising ambient temperatures on reproductive health of domestic animals, and specifically mares in this case, can provide insights that may help minimize the risk of embryo loss during the critical gestation period.
• It also throws light on the need to prepare and plan for heatwaves and devise effective strategies to prevent or minimize such embryonic losses in mares.