Genetic parameters for earnings in Quarter Horse.

This research revolves around the evaluation of heritability of earnings in the Quarter Horse and its potential inclusions in breeding programs. Utilizing records from races spanning multiple years, the study explores the significance of various factors on the horse’s performance and financial return, concluding that earnings are under selective pressure and can be included in breeding programs.

Objective and Methodology

• The main objective of this research was to estimate the heritability (h(2)) of earnings in the Quarter Horse. This understanding would help decide if it can be leveraged in breeding programs.
• For the evaluation, the researchers utilized records from 14,754 races involving 2443 horses. The data spanned over three decades from 1978 to 2009, and was obtained from Sorocaba Hippodrome, São Paulo, Brazil.
• All predecessors of the horses registered were included in the pedigree up to the fourth generation. Log-transformed performance measures (LPM), which are the performance measures adjusted through logarithmic transformation, were analyzed for horses of 2, 3, and 4 years of age as well as throughout their whole career.
• The heritability estimates were derived using a multi-trait model and Gibbs sampling. Various factors were included in the analyses, such as the sex of the horse, the year of the race, and the individual horse.

Analysis and Comparison

• Five different analyses were conducted, including one where the LPM was divided by the number of prizes, one where the LPM was divided by the number of race starts, and three analyses incorporating the number of prizes, the number of race starts, and both (LPM_cNPS) as covariates.
• The analysis was also performed separately to consider the inclusion and exclusion of the maternal effect on the horse’s performance.
• The models were compared using the deviance information criterion, which revealed that LPM_cNPS incorporating maternal effects emerged as the best model.

Conclusion

• The study found that the h(2) estimates were 0.19 ± 0.08, 0.21 ± 0.08, 0.22 ± 0.09, and 0.21 ± 0.07 for earnings at 2, 3, and 4 years old, and total career, respectively.
• These results indicate that earnings in the Quarter Horse are under selection.
• Consequently, it is suggested that earnings could be included as a factor in breeding programs with a view to enhancing the racing performance of future generations of Quarter Horses.