Dairy Herd Genetic Differences for Lactation Production

Evaluation of Phenotypic and Genetic Trends in Weaning Weight in Angus and Hereford Populations in Virginia1

“…The widespread use of artificial insemination, which produces large half-sib groups among dairy herds across the nation, has generated an increasing interest among dairy scientists in evaluation of genetic progress at different time intervals. For example, estimation of genetic trends for dairy cattle performance traits reported by Van Vleck and Henderson (1961), Arave et al (1964), Everett et al (1967), Harville and Henderson ( 1967), Powell and Freeman ( 1974), Tomar and Singh ( 1981) and Schaeffer et al ( 1982) cover the literature on most trend evaluation studies in dairy cattle. In comparison, the few available early studies in beef cattle have been 4 confined to small, closed nerd populations (Brinks et al, 1961(Brinks et al, ,1965Armstrong et al, 1965;Nelms and Stratton, 1967;Baily et al, 1971;Schalles and Marlowe, 1971 (Kennedy and Henderson, 1977;Schaeffer et al, 1981;Crow and Howell, 1983;Zollinger and Nielsen, 1984 (Broy et al, 1962;Orozco and Bell, 1974) (Rendel andRobertson, 1950, Acharya andLush, 1968) and in sheep (Peters et al , 1961 Giesbrecht and Kempthorne (1965) in poultry and Burnside and Legates ( 1967) in dairy cattle to estimate environmental and genetic trends.…”

Intraherd prediction of beef cattle genetic values using linear model techniques

“…Bereskin and Freeman (1965) show a large reduction in the herdyear-season variance component as a fraction of the variation within herd-year-season groups when computing selection indices from records deviated from a herdmate average adjusted for genetic differences among groups; however, the appropriate adjustment for Intraherd mixed-model evaluations has not yet been clarified. Dairy Industry programs based on Henderson's (1975b) Intraherd model assume that all herd differences are environmental and Bolgiano et al (1980) and Schaeffer et al (1982) conclude that this assumption of a common genetic base has little effect on interherd comparisons.…”

“…This casts doubt on the assumption of a common base for the calf and sire information as well as on the applicability of using sire predictors intended to predict the average performance of a randomly chosen group of calves.While the literature considers only the incorporation of sire predictors, the incorporation of cow predictors from other intraherd evaluations should be possible with the same technique, assuming a suitable base adjustment. This would overcome many of the disadvantagesSchaeffer et al (1982) list for intraherd cow evaluation, aiding, for…”