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Genetics of Racing Performance in the American Quarter Horse: I. Description of the Data^{1, 2,}

Iowa State University, Ames 50011 and Colorado State University, Fort Collins 80523

Abstract

More than 1 million racing records of American Quarter Horses were used to provide a description of Quarter Horse racing data. The data presented five racing distances (201, 320, 366, 402 and 796 m). Finish time was used to measure racing performance. Means and variances for finish time increased with length of the race, but the distributions were similar for the five distances. Each distribution was skewed to the right and more peaked than a normal distribution. Repeated records were an important source of information and their use should improve the accuracy of genetic evaluations when comparing horses and sires across races and tracks. There was a tendency for more older horses and geldings to be found in the longer races. Two-year-old horses raced almost exclusively against other 2-yr-olds, and most 3-yr-olds raced with horses their own age. An interaction was detected between sex and age that was interpreted to be the result of differential selection rates among the sexes. Further study of age and sex effects is needed to develop factors for adjusting Quarter Horse racing data for use in genetic evaluation.

¹ Journal paper no. J-12802 of the Iowa Agric. and Home Econ. Exp. Sta., Ames. Project no. 0155.

² The cooperation and financial assistance of the American Quarter Horse Association is gratefully acknowledged.

³ Present address: DeKalb Swine Breeders, 3100 Sycamore Road, DeKalb, IL 60155.

⁴ Dept. of Anim. Sci., Iowa State Univ., Ames 50011.

⁵ Dept. of Anim. Sci., Colorado State Univ., Fort Collins 80523.