Bivariate animal model estimates of genetic, phenotypic, and environmentalcorrelations for production, reproduction, and somatic cells in Jerseys

Correlations were obtained between 18 response variables of a Jersey herd ( Florida Agricultural Experiment Station, Gainesville) for 374 first lactati ons. Estimates were from the use of multivariate, derivative-free, restrict ed maximum likelihood procedures with the simplex method of partial maximiz ation. Estimates agreed closely with those obtained previously by other met hods in this and other dairy populations. All correlations between yields w ere high and positive; those between yields and days from parturition to fi rst service were negative and near zero. Correlations between yields and so matic cell scores were moderate and negative; those between yields and cons tituent percentages in general were negative, except for the yield and perc entage of the same constituent. Genetic correlations between chloride conte nt and somatic cells and between measures of somatic cells were 1.0. Result s suggest that single-trait selection for milk yield should result in corre lated increases in constituent yields with slight decreases in percentage c omposition of constituents and somatic cell counts.