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Effect of Herd, Year, Age, and Stage of Location on Jersey Type Classifications

Animal Improvement Programs Laboratory, Animal Physiology and Genetics Institute, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD 20705
American Jersey Cattle Club, P.O. Box 27310 Columbus, OH 43227

ABSTRACT

Jersey type classifications in the United States from 1968 to 1976 were examined to determine which environmental sources of variation affected final score and 14 component traits. Year explained 1 to 4% of the variation in type traits. Herd-year effects explained 21% of the variation in final score and 14 to 18% in the component traits. The recommendation is that sire evaluation be within herd-year. Age effects were significant for all traits. The greatest effect was on body capacity and dairy character, changing multiple correlation squared by 10.1 and 7.6%, and the least effect was on mammary and feet and legs. Effects of stage of lactation were small for all traits except body capacity and dairy character. Interaction of age by stage of lactation changed multiple correlation squared by only .1 to .3% in all traits. Separate ratio factors for adjustment were developed for age and stage of lactation. Repeatabilities estimated by the regression of later on earlier classification scores for these same traits within herd-year were highest for final score, stature, and general appearance (.67, .60, and .51) and lowest for feet, legs, and dairy character (.27, .29, and .30).