Genetic parameters for racing records in trotters using linear and generalized linear models.

This research explored the role of genetics in the performance of trotting racehorses. By analyzing over half a million records from two breeds of trotters, the study assessed the heritability and repeatability of several racing traits. Results showed that traits such as racing time have higher heritability, suggesting effective selection of horses for specific traits is possible based on a few repeating records.

Research Design

• The data involved over a million records for two horse breeds: 17,792 Finnhorses and 25,536 Standardbred trotters.
• Researchers estimated the heritability and repeatability of race performance in these horses using linear and generalized linear models.
• The racing traits that were analyzed included racing time, earnings from races, single placings, victories, incidents of breaking stride, and disqualifications.

Major Findings

• The heritability of racing time was highest, varying between 0.32 and 0.34. In genetics, heritability refers to the proportion of observed differences in a particular trait among individuals within a population that are due to genetic differences. Therefore, the data indicates that more than 30% of the differences in racing times among these trotters can be attributed to their genetic makeup.
• Heritability estimates were considerably lower for earnings from single races, only ranging from 0.01 to 0.09. Thus, earnings are largely influenced by factors other than genetics.
• The heritability of annual earnings, however, was moderate, 0.19 for Finnhorses and 0.27 for Standardbred trotters, indicating that over a longer term, genetic factors may play a more significant role in race earnings.
• Heritability estimates for racing success variables (placings, winnings, breaking stride, and disqualifications) were on the lower side, varying between 0.04 and 0.12, implying these factors may be more influenced by environmental factors or training, than by genetics.
• The study found high genetic correlation among racing traits, suggesting that selecting for certain traits would also likely result in improvements in genetically correlated traits. By contrast, phenotypic correlations (correlations in physical characteristics) were generally low to moderate.

Implications

• The findings suggest that selection of horses for traits like racing time, based on a few repeated records, can be effective due to the moderate heritability and high repeatability of such traits.
• However, selection for traits like single earnings facets may not be as fruitful due to their lower heritability.
• Given the high genetic correlations observed, direct selection for racing time and annual earnings may also lead to good genetic response in overall racing success.