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Genetic effects and relationship of milk production and percentage of white coat in a subtropical holstein herd^*

Carlos M. Becerril P.^I; Charles J. Wilcox^II; Miguel Santiago Campos^II; Peter J. Hansen^II

^IColegio de Postgraduados, Chapingo, Mexico
^IIDairy Science Department, University of Florida, PO Box 110920, Gainesville, FL 32611-0920, USA. Send correspondence to C.J.W.

ABSTRACT

First lactations of 795 cows in the Florida Agricultural Experiment Station dairy herd from 1960 through 1989 were analyzed. Percentage of white coat was obtained by visual evaluation of drawings on registry certificates. Phenotypic correlation between percentage of white (WP) on the two sides of the body was .97 (P < .01). The distribution of individual percentages was not normal (P < .01) (skewed to the right), with mean, standard deviation, median and mode of 23.9, 25.6, 15 and 0, describing a mostly black cow sample. Least squares means for milk and fat yields, fat percent and percent white were 4556 kg,166 kg, 3.46%, and 23.5%. Percentage white was related linearly (positively) with milk yield, with p = 2.75 kg (per 1% white). Interactions of percentage white and calving season were detected for fat yields; regressions were b = .21 kg and b = .002 kg for cool (Oct - Mar) and warm (Apr - Sept) seasons. Interaction also was important for fat percentage. Heritability of percentage white from intraclass (paternal half-sib) correlation was .77; genetic correlations of white color with milk yield, fat yield and fat percent were -.12, -.39, and -.38. Additional research seems warranted to establish the relationships of percentage white color and economically important traits of dairy cattle.

Keywords: genetic effects; milk production; white coat; holstein herd.

REFERENCES

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* Florida Agricultural Experiment Station Journal Series No. R02919.