Transformation of Measurements Percentage of White Coat Color for Holsteins and Estimation of Heritability

¹ Dairy Science Department, University of Florida, Gainesville 32611
² Animal Improvement Programs Laboratory, Agricultural Research Service, USDA, Beltsville, MD 20705
³ Mathematics Department, University of Florida, Gainesville 32611

Percentage of white coat color was measured on registration certificates of 4293 Holstein heifers on eight dairy farms in Florida. Measurements of white percentage were by visual evaluation on one side of the upper body (head, neck. and trunk) only and obtained in increments of 5%. Mean, median, mode, standard deviation, and skewness of white percentage were 25.6, 15, 0, 26.9, and 1.03. Distribution of white percentages showed lack of normality. Original data were transformed using an extension of the Box-Cox transformation to approach normality and to provide maximum likelihood estimators of the transformed parameters. Heritability estimates for percentages of white coat color were computed using derivative-free REML with an animal model. Estimates of heritability were .715 from untransformed data and .779 for transformed. Standard errors of estimates were slightly lower (.032 vs. .035) following transformation. Additional study to find an improved transformation procedure still seems warranted.

Key Words: coat color • heritability • Holstein

Submitted on September 20, 1993
Accepted on April 11, 1994