EFFECT OF FULL SIBS ON ADDITIVE BREEDING VALUES UNDER THE DOMINANCE MODEL FOR STATURE IN UNITED-STATES HOLSTEINS

Differences in breeding values between dominance and additive models w ere examined theoretically and with field data. Data included 5.2 mill ion records on stature from 3.0 million US Holsteins. The largest full -sib family had 29 animals, and 7% of all animals had at least one ful l sib. The dominance model, which accounted for dominance covariances, included the following effects: management, age, stage of lactation, permanent environment, animal additive, and parental dominance tone-qu arter of dominance variance) as well as a regression coefficient for i nbreeding percentage. Two reduced models were also assumed; in the fir st, the parental dominance effect was removed, and, in the second, the inbreeding regression coefficient was also removed. The correlations between breeding values in the three models were >0.999, but breeding values of some animals from full-sib families changed >5 standard devi ations of parental dominance. The largest changes were observed for pa rents with large numbers of full-sib progeny, with limited information from parents, and without individual performance records. On average, the differences were up to four times larger for cows than for bulls and up to five times larger for dams than for sires. The greatest diff erences in breeding values between the dominance and the additive mode ls were observed for dams with full-sib progeny, female fill sibs, and low reliability bulls with full sibs in the extended family. Animals with large amounts of additive information as progeny-tested bulls wer e influenced little by the inclusion of dominance. Animals with a larg e proportion of information coming from animals with dominance relatio nships, such as cows originating via embryo transfer changed the most.