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Phenotypic, Genetic, and Environmental Relationships of Milk Production and Type Ratings of Holstein Cows¹

Department of Dairy Science, New Jersey Agricultural Experiment Station, Sussex

ABSTRACT

Data from 233 Holstein cows with 671 lactation records and 2,272 classification scores were analyzed. Milk records were adjusted to a 2x, 305-day M.E. basis; type scores were adjusted for the effects of age, season, stage of lactation, classifier, and year. Repeatability of single-lactation records for milk yield, 4% FCM yield, and fat yield ranged from 0.53 to 0.56, with an estimate of 0.75 for fat percentage. Heritabilities of single records for the three measures of yield were 0.12 to 0.14, and for fat percentage, 0.69. Heritability estimates for the average number of records per cow (2.88), and for an infinite number of records per cow, were also calculated. Repeatabilities of type scores based on a single classification were from 0.24 to 0.56, with heritabilities from 0.09 to 0.27. Phenotypic correlations between over-all rating and measures of yield ranged from 0.13 to 0.15; between subratings and yield, from 0.18 to 0.20 for dairy character to 0.05 to 0.07 for rump. Correlations between fat percentage and type were essentially zero.

Environmental correlations between type and measures of yield were positive and from 0.05 to 0.21. Genetic correlations were also positive but low; the highest 0.26 between fat yield and dairy character. Genetic correlations among type scores ranges from –0.02 to +1.11. Genetic correlations for production were: milk yield with 4% FCM 0.78, with fat yield 0.74, and with fat percentage –0.02; 4% FCM yield with fat yield 0.96, with fat percentage 0.13; fat yield with fat percentage 0.21.

¹ Paper of the Journal Series, New Jersey Agricultural Experiment Station, Rutgers—the State University, New Brunswick. This investigation was supported in part by funds provided by the Charles H. Hood Dairy Foundation, Boston, Massachusetts, and through cooperation of the Holstein-Friesian Association of America.

² Present address: Department of Dairy Science, University of Florida, Gainesville.

³ Computation Center, Rutgers—the State University.

⁴ Deceased October 28, 1961.