http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
development and genetic evaluation of racing capacity in Thoroughbreds
xiii, 165 leaves : illustrations ; 29 cm
Genetic parameters were estimated for three measures of racing capacity in Thoroughbreds; (1) mean seconds per furlong of the race (MSPF-Race); (2) mean seconds per furlong of the stretch (MSPF-Stretch), the portion of the race in which most horses run at their maximum ability; and (3) dollar earnings. Heritabilities, repeatabilities, and correlations were estimated from the race records of 1,787 Thoroughbreds 3 yr of age and older that had started in races ranging in distance from 3/4 mile (6 furlongs) to 1 1/2 miles (12 furlongs) at four tracks during 1982 and 1983. A total of 5,930 starts from 545 progeny groups were analyzed within age groups of 3, 4, and 5 yr of age and older using least-square procedures. Two measures of pace were included as covariates in the initial analyses to account for within race tempo and strategy. Pace significantly influenced (p<.001) the variation of MSPF-Race and MSPF-Stretch. The pace variables were mean seconds per furlong of the leader at the last point of call and at the finish. These effects were highly confounded with sire and were not included in subsequent analyses. Horses and sires were not completely cross-classified with distance, therefore age group data were separated into distance categories of sprints (6 to 7 furlongs) and routes (8 to 12 furlongs) for final analyses. Negative sire components were estimated for MSPF-Race from 3- and 4-yr-old sprint data, for MSPF-Stretch from 3-yr-old sprint and 4-yr-old route data, and for earnings from 5-yr-old and older data. Sampling error by way of small numbers of offspring per sire (adjusted number = 2 to 3.4) and confounding of sire with fixed effects were thought to be the main causes for these negative estimates. The most accurate genetic parameter estimates were considered to be from pooled age-distance data that had positive sire components of variance. Respective estimates of heritability and repeatability were .30 ± .13 and .42 ± .04 for MSPF-Race, .28 ± .11 and .34 ± .03 for MSPF-Stretch, and .32 ± .07 and .29 ± .03 for earnings. Genetic correlations were .81 ± .15 between MSPF-Race and MSPF-Stretch, -.89 ± .05 between MSPF-Race and earnings, and -.58 ± .16 between MSPF-Stretch and earnings.
Ph. D. in Animal Breeding Texas A & M University 1987
Includes bibliographical references (leaves 148-160).