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Title: Effectiveness of genetic evaluations in predicting daughter performance in individual herds

item Norman, H
item Wright, Janice
item Dechow, C
item Goodling, Jr, R

Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 3/8/2010
Publication Date: 6/24/2010
Citation: Norman, H.D., Wright, J.R., Dechow, C.D., Goodling, Jr, R.C. 2010. Effectiveness of genetic evaluations in predicting daughter performance in individual herds. Journal of Dairy Science. 93(E-Suppl. 1):612(abstr. W90).

Interpretive Summary:

Technical Abstract: Response to genetic selection has been demonstrated nationally for US dairy cattle, but producers are more likely to appreciate the value of genetic selection if trends within their own herds can be shown. Responses from 2004 through 2008 in individual herds by Holstein and Jersey cows were documented for yield (milk, fat, and protein), somatic cell score, productive life, and daughter pregnancy rate. Sire and dam predicted transmitting abilities (PTA) or parent average (PA) from evaluations prior to first calvings were the independent variables, and phenotypic performance (standardized first-parity yields, somatic cell score, lifetime days milked, and days open) was the dependent variable. Minimum number of cows with usable records per herd was 50. Mean coefficients for regression of standardized yield on PA for the same trait was 0.73 for milk, 0.79 for fat, and 0.69 for protein for 8,257 Holstein herds and 0.79, 0.72, and 0.73 for 441 Jersey herds. The majority of individual herd regression coefficients for yield traits were between 0.3 and 1.0; their standard deviations were between 0.38 and 0.47. Regression coefficients may have been <1.0 because PA was based on all-parity yield whereas phenotypic yield was only from first parity or because the heritability assumed for calculating PTA was too high. Mean regression coefficients for somatic cell score, productive life, and daughter pregnancy rate were 0.82, 0.65, and 0.81, respectively, for Holsteins and 0.65, 0.56, and 0.85 for Jerseys; their corresponding standard deviations were 0.66, 0.75, and 1.07 for Holsteins and 0.77, 0.80, and 1.14 for Jerseys. Mean coefficients for regression of sire PTA on phenotypic performance ranged from 0.53 to 0.80; mean regression coefficients for dam PTA ranged from 0.43 to 0.86. Although standard errors were large, response to genetic selection on a within-herd basis could be demonstrated, which should help increase confidence in national genetic evaluations.