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

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Abstract
Jersey type classifications in the USA from 1968-1976 were examined to determine which environmental sources of variation affected final score and 14 component triats. Year explained 1-4% of the variation in type traits. Herd-year effects explained 21% of the variation in final score and 14-18% 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%; 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-.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).