Journal of Dairy Science, Vol 77, Issue 9 2651-2657, Copyright
© 1994 by American Dairy Science Association
Transformation of measurements percentage of white coat color for Holsteins
and estimation of heritability
C. M. Becerril, C. J. Wilcox, G. R. Wiggans and K. N. Sigmon
Dairy Science Department, University of Florida,
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.