JDS
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Journal of Dairy Science Vol. 57 No. 10 1228-1233
© 1974 by American Dairy Science Association ®
This Article
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Powell, R. L.
Right arrow Articles by Freeman, A. E.
Right arrow Search for Related Content
PubMed
Right arrow Articles by Powell, R. L.
Right arrow Articles by Freeman, A. E.

Estimators of Sire Merit1

R. L. Powell2 and A. E. Freeman

Department of Animal Science, Iowa State University, Ames 50010

ABSTRACT

Nearly 7,000 first lactations of daughters of 90 sires 187 progeny test herds were used to compare estimators of sire merit. The standard model among the several contains fixed effects of herd-year-seasons and sire groups and random effects of error and sires within groups. The estimate of merit for a sire is the sum of the appropriate group and sire within group estimates from a generalized least squares solution. This approach accounts for sires of hedmates, considers the number of daughters and herdmates in each herd-year-season, and simultaneously regresses sire constants toward appropriate group means. Three definitions of groups, as well as a model not including groups, were compared with the conclusion that virtually any grouping is preferable to ignoring groups for sires in general. Two herdmate comparisons, Predicted Difference, and regressed-mean weighted difference were compared, and evaluations by the latter approach were more like those from standard method. Both herdmate comparisons ignore the merit of sires of herdmates. Neither this omission nor ignoring environmental correlation seriously altered evaluations of the majority of sires.

FOOTNOTES

1 Journal Paper J-7790 of the Iowa Agriculture and Home Economics Experiment Station, Ames, IA, Project 1053 as a collaborator under the North Central Regional Project, NC-2, Improvement of Dairy Cattle Through Breeding.

2 Present address: Animal Improvement Programs Laboratory, Agricultural Research Service, USDA, Beltsville, MD 20705.






HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 1974 by the American Dairy Science Association ®.