Climatic factors affecting gestational length in mares under subtropical climate.

This research analyzes how climatic factors impact the length of horse pregnancies, while also considering factors such as foal gender, sire, and various maternal attributes.

Objective of the Study

• The research has a twofold purpose. First, it seeks to investigate the role that climatic elements play in determining the length of a horse’s pregnancy, referred to as gestational length (GL). Second, it aims to discover any relationships between the GL and other attributes such as the sire (father), the foal’s gender, and maternal factors.

Methodology Adopted

• The researchers extracted data retrospectively from 470 pregnancies of 202 different mares from a Criollo breeding farm in the south hemisphere. They considered the interval between the mare’s ovulation and parturition as the GL.
• They also obtained and documented daily climatic and environmental data such as temperature, relative humidity, daily sunshine hours, precipitation, and the temperature humidity index (THI).
• A multiple factor analysis of variance was performed to identify relationships and interactions between the GL and several independent variables such as foal’s gender, maternal attributes, sire, as well as weather conditions throughout the year.

Key Findings

• They found the average gestation period for the 470 pregnancies to be 337 days, with lengths varying from 311 to 363 days.
• Significantly, young mares experiencing their first pregnancy had longer gestations compared to young and mature mares who had been pregnant before.
• Interestingly, the gender of the foal had no impact on the length of the pregnancy, while the sire did have an influence.
• Mares that went through their pregnancy during autumn and winter, specifically when there were fewer daily sunlight hours, had an increase in gestational length.

Conclusions Drawn

• The study concluded that environmental and climatic factors significantly influenced a horse’s gestational length. Particularly, the amount of daily sunshine, precipitation, and the THI were found to be negatively correlated with the length of the gestation.
• Also, young mares giving birth for the first time experienced longer pregnancies compared to young and mature mares who had given birth previously.