Environmental and Genetic Trends in Production and Their Effects on Sire Evaluation

Abstract

The objectives of the investigation were to estimate, from DHIA records initiated between December, 1956, and November, 1962, the magnitudes of the intraherd environmental and genetic trends in the milk and milk fat production of the New York State, Holstein, artificially sired, DHIA population and to determine the effects of these trends on the New York State sire-evaluation procedures. The total intraherd trend was estimated to be 176±8kg of milk and 6.4±0.3kg of milk fat per year. Estimates of the intraherd environmental and genetic trends indicated an environmental trend of 128±17kg of milk and 4.9±0.7kg of milk fat per year and a genetic trend of 47±17kg of milk and 1.5±0.6kg of milk fat per year.Product-moment correlations between standard estimates of sire breeding values and estimates adjusted for the effects of the genetic trend were close to one. However, there were two categories of sires where significant differences between the two types of proofs were noted: 1) sires that had not recently been used in the population, and 2) sires that had above or below average birth dates and, in addition, had relatively few daughters.