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


     

Journal of Dairy Science Vol. 77 No. 3 883-890
© 1994 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 Similar articles in PubMed
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 HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Powell, R. L.
Right arrow Articles by Norman, H. D.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Powell, R. L.
Right arrow Articles by Norman, H. D.

Effect of Sampling Status and Adjustment for Heterogeneous Variance on Bias in Bull Evaluations

R. L. Powell 1, G. R. Wiggans 1, and H. D. Norman 1

1 Animal Improvement Programs Laboratory, Agricultural Research Service, USDA, Beltsville, MD 20705-2350

Holstein bulls were assigned to sampling categories (AI stud, AI nonstud, or non-AI) based on bull code, controller number, and age at semen distribution. The AI stud bulls were sampled through traditional progeny-testing programs of 13 AI organizations; AI nonstud bulls had AI semen collection reported by another organization or by multiple organizations. The non-AI bulls had no reported AI semen collection. Actual daughter yield deviations for these three groups of bulls were compared with expected performance (parent average) to provide an indication of whether evaluations were free from bias for daughter yield deviations. Mean difference of daughter yield deviation from parent average was close to 0 kg for animal model evaluations of all 22,930 bulls but was positively biased by 46 kg of milk for AI nonstud bulls. Mean PTA and reliabilities for parents were highest for AI stud bulls and lowest for non-AI bulls. The AI stud bulls varied least and were intermediate for mean management, approximated as mean daughter yield minus bull ETA. Management was highest for AI nonstud bulls, which suggested that adjustment for heterogeneous variance might reduce bias. However, the effect of this adjustment on mean difference of daughter yield deviation from parent average was small.

Key Words: bias • heterogeneous variance • sampling status • evaluation adjustment

Submitted on May 27, 1993
Accepted on October 18, 1993




This article has been cited by other articles:


Home page
 J ANIM SCIHome page
M. D. Gomez, F. Goyache, A. Molina, and M. Valera
Sire x stud interaction for body measurement traits in Spanish Purebred horses
J Anim Sci, August 1, 2009; 87(8): 2502 - 2509.
[Abstract] [Full Text] [PDF]

Home page
 J DAIRY SCIHome page
C. D. Dechow and H. D. Norman
Within-Herd Heritability Estimated with Daughter-Parent Regression for Yield and Somatic Cell Score
J Dairy Sci, January 1, 2007; 90(1): 482 - 492.
[Abstract] [Full Text] [PDF]

Home page
 J DAIRY SCIHome page
R. L. Powell, A. H. Sanders, and H. D. Norman
Accuracy and Stability of National and International Somatic Cell Score Evaluations
J Dairy Sci, July 1, 2005; 88(7): 2624 - 2631.
[Abstract] [Full Text] [PDF]

Home page
 J DAIRY SCIHome page
R. L. Powell, A. H. Sanders, and H. D. Norman
Stability of Genetic Evaluations for Active Artificial Insemination Bulls
J Dairy Sci, August 1, 2004; 87(8): 2614 - 2620.
[Abstract] [Full Text] [PDF]


HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 1994 by the American Dairy Science Association ®.