Department of Animal Science
Date of this Version
January 1987
Abstract
Heritability estimates, by year of freshening of daughter, were obtained from daughter-dam and granddaughter-granddam regressions using 61,482 triply matched first lactations of artificially sired Holstein cows obtained from the Northeast Dairy Records Processing Laboratory. After adjusting for herd-yearseason effects, residual effects may include additive and other genetic effects of the animal, maternal effects, cytoplasmic effects, and other environmental effects. Analysis of residuals showed that cytoplasmic effects accounted for no variation in milk and fat yield and fat percent. Weighted yearly heritability estimates and standard errors from daughter on dam regressions were .35 + .01 for milk yield, .30 + .01 for milk fat yield, and .63 -+ .01 for milk fat percent and from daughter on granddam regressions were .34 -+ .03 for milk production, .28 -+ .03 for milk fat production, and .55 +- .03 for milk fat percent. The differences between daughter-dam and daughter-granddam heritability estimates, which estimate twice the fraction of variance due to cytoplasmic effects, were negative and not statistically significant for milk fat yield and also were negative but highly significant for milk fat percent.
Comments
Published in J Dairy Sci1987, 70:837-841. Copyright © 1987 The American Dairy Science Association. Used by permission.