ABSTRACT
First lactation records of 109,589 cows in 1,978 Holstein herds cooperating with three artificial insemination studs in young sire sampling were studied to compare performance of progeny of approximately the upper 15, 2, and 25% of sires, dams, and maternal grandsires for milk yield with selection differentials of +350, +2735, and +268 kg milk when the young sires entered sampling programs. The 315 young bulls were sired by 88 sires. Mean weighted Predicted Differences for sires proven through artificial insemination were 130 kg milk and 4.0 kg fat, whereas weighted averages for naturally proven sires were 13 kg milk and .4 kg fat. For young sires, pedigree index of sire, dam, and maternal grandsire averaged 347 kg milk and 11.8 kg fat, and for an index including sire and maternal grandsire averaged 242 kg milk and 7.6 kg fat. Annual trends for ancestors were +31.8 kg milk and +.9 kg fat for sires. Within herd-year-season, production of daughters of progeny tested sires exceeded that of daughters of young sires by 84 kg milk and 2.4 kg fat. Progeny of young sires produced 103 kg more milk than daughters of naturally tested bulls.
