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Journal of Dairy Science Vol. 62 No. 11 1774-1783
© 1979 by American Dairy Science Association ®
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Estimation of Milk Producing Ability of Holstein Cows1

Shuang-Chinq Chyr2, A. E. Freeman and Jeffrey Berger

Department of Animal Science, Iowa State University, Ames 50011

ABSTRACT

Producing abilities of Holstein cows were estimated and compared through four procedures: herdmate comparison with (new) and without (old) adjustment for herdmates' estimated average transmitting abilities, and best linear unbiased prediction with and without considering cow selection. Increase of heritabilities by adjusted herdmates as compared with unadjusted was from .28 to .30 for deviations of first lactations and from .23 to .25 for deviations of the first four lactations. Repeatabilities by both herdmate comparisons were the same, .50. Both best linear unbiased predictions also had the same repeatabilities and the same heritabilities (.54, .35 for the first laction; .54, .32 for the first four lactations). Correction for cow selection did not improve the accuracy of prediction. Best linear unbiased prediction is superior to herdmate comparison both in removing effects of herd-year-seasons from herdmate deviation records and improving the accuracy of predicting producing ability.

Methods of estimating producing ability with deviation records, constant correlation, actual correlations, and generalized least-squares did not differ appreciably from each other in prediction within each procedure. When producing ability is obtained by generalized least-squares, however, the first lactation gets the largest weight but is the poorest predictor.

FOOTNOTES

1 Journal Paper No. J-8986 of the Iowa Agriculture and Home Economics Experiment Station, Ames. Project No. 1053, a contributing project to North Central Regional Project NC-2, Improvement of Dairy Cattle through Breeding.

2 Department of Animal Husbandry, National Taiwan University, Taipei, Taiwan 107, Republic of China.






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Copyright © 1979 by the American Dairy Science Association ®.