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Linear Type Trait Analysis with Genetic Parameter Estimation¹

Iowa State University, Ames 50011

A. Kuck

21st Century Genetics Cooperative, Shawano, WI 54166

ABSTRACT

Data on 18 traits scored 1 to 50 from 21st Century Genetics mating appraisal program were analyzed. Cows (43,428) were scored for 16 traits by 21st Century Genetics evaluators; disposition and milk-out were scored by the herd owner. Data were collected from September 1, 1979 to January 1, 1984. Significant sources of variation were herd-year of evaluation, age of animal, stage of lactation, and sire. Parameters were estimated by using a multiple-trait model that included herd-mate deviations for milk and fat as additional traits. Means ranged from 25.1 to 31.8, and standard deviations ranged from 5.54 to 9.07. Genetic correlations ranged from –.50 to .91 and generally are larger than their corresponding phenotypic correlations. Genetic correlations >¦.50¦ were found between traits close in physical proximity or similarly defined. Heritabilities ranged from .08 to .42 and generally tended to be smaller than those previously estimated. All traits had significant least squares solutions for stage of lactation, but solutions were small (<5 points) to negligible. Corrections for age at first parity were small (<3 points) in all instances. Correcting scores for age at first parity and stage within first lactation for many traits seems relatively unimportant.

¹ Journal Paper Number J-12623 of the Iowa Agriculture and Home Economics Experiment Station, Ames. Project Number 1053.

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