Genetic and Environmental Factors Influencing Gestation Length in Lusitano Horses.

This study examines the factors that influence gestation length in Lusitano horses. It found that mare age, conception month, and the specific stallion used for breeding had significant effects, but the sex of the foal and inbreeding did not.

Objective of the study

• This research was conducted with the aim of identifying the genetic and environmental factors influencing gestation length in Lusitano horses.

Methodology

• The researchers collected breeding and parturition records of Lusitano horses over a period of 35 years from the Alter Real stud.
• They calculated gestation length using data from 1027 gestations involving 209 mares and 60 stallions.
• A mixed model analysis of variance was used to identify factors affecting gestation length.

Results

• The average gestation length was found to be 338.1 ± 9.26 days.
• The sex of the foal and inbreeding of the dam and foal were found not to significantly affect the gestation length.
• Gestation length increased with the age of the mare, and gestation length was longer when conception occurred between January and April.
• The specific stallion used in breeding played a significant role in gestation length, with most stallions resulting in gestation length within an interval of ±5 days.
• Analysis made with the inclusion of the mare as a random effect resulted in a repeatability estimate of 0.427, pointing out the tendency of mares to have a consistent gestation length over time.

Conclusions

• The heritability estimates were 0.39 for maternal genetic effects and 0.19 for direct genetic effects. No association was found between these two components.
• Overall, besides the genetic influence that the mare has on gestation length, environmental factors such as the month of conception and the age of the mare also have a significant impact on how long gestation lasts in Lusitano horses.