An analysis of stallion fertility rates (foals born alive) from the breeding documents of the Landgestüt Celle over a 158-year period.

The research examined the fertility rates of stallions in the Hannoverian breed in Germany between 1815 and 1973, and concluded that there was no significant improvement in reproductive rates over that time period. The research also observed that stallion fertility remained high until the number of mares covered by a single stallion exceeded 80, and typically only dropped significantly as the stallions aged.

Overview of the Research

• This research study conducted an extensive examination of the fertility rates of stallions over a prolonged period of 158 years, specifically from 1815 to 1973.
• The study involved analysing breeding documents from the Landgestüt Celle, which is a significant horse breeding establishment in Germany.
• The researchers specifically focused on the Hannoverian breed, a German warmblood horse breed that has been reputable for high breeding quality.

Key Findings

• One of the most substantial findings of this research was that the reproductive rates of the studied breed did not improve during the period under review. Despite advances in equine breeding and healthcare, the rates remained between 50% and 60%.
• Notably, the only periods where foaling percentages deviated from this norm were the decades that included the two World Wars and their aftermaths. The study, however, did not provide specific details or reasons for these exceptions.
• The research also revealed that fertility remained high until a single stallion covered more than 80 mares annually. This finding suggests that there could be a limit to the number of mares a single stallion can effectively breed with within a year.
• Further, the study observed that stallion fertility remained impressive throughout the reproductive lifespan of the stallions studied except for the oldest one who was 32 years old. At this old age, there was a significant lowering of fertility, supporting the notion that aging comes with decreased fertility.