Determinants of gestation length in Thoroughbred mares on German stud farms.

This research article investigates the factors influencing the length of gestation in Thoroughbred mares in German stud farms. Among these factors are the age of the stallion and mare, the gender of the offspring, and the breeding histories of the mares.

Objective of the Research

The primary purpose of this research was to evaluate how various factors impact the gestation length in Thoroughbred horses. These factors include:

• The ages of both the mare and the stallion involved in breeding
• The unique specifics of the mare’s maternal lineage
• Additive genetic effects from the dam, stallion, and fetus

Methods Used in Research

Data for this research was gathered from records of 16,226 pregnancies involving 5959 Thoroughbred mares and 290 different stallions from the years 1993 through 2009. The methods involved the use of linear mixed models for analysis of these records.

Key Findings

The research showed that:

• A stallion’s age mattered – stallions that were 17 years or older resulted in significantly longer gestation periods compared to younger stallions
• Increasing mare’s age led to a significant increase in gestation length
• Male foals resulted in longer gestation periods
• Factors like the month and year of breeding and the breeding history (parity and reproductive status) of the mare also influenced the gestation length
• The mare and stallion’s individual characteristics explained 18% and 4% of the variance in gestation length respectively
• There was no significant effect of mare and foal inbreeding coefficients on gestation length
• Mare’s gestation length was related to heritable characteristics with heritability for the mare being 0.17 and for the fetus being 0.006; a paternal genetic effect was not estimable
• The additive genetic and permanent environmental contributions of the mare were in proportions of about 76.5% and 23.5% respectively
• There was no apparent effect of the mare’s maternal lineage on the gestation length

These findings provide valuable insights for breeding Thoroughbred horses, with implications for ensuring optimal breeding age for both mares and stallions and considering the potential gender of the offspring.