Analysis of Covariance Structure of Repeated Measurements in Holstein Conformation Traits

¹ Department of Animal Production, Faculty of Agriculture, University of Ain Shams, Shubra Al-Khaima, Cairo, Egypt
² Department of Dairy Science, University of Wisconsin-Madison, Madison 53706
³ Holstein Friesian Association of America, Brattleboro, VT 05301

A model was proposed and tested for explaining observed structures of (co)variances for a multiply measured conformation trait, final type score, in Holstein cattle. Typically, second and later measures on the same animal showed increased variance and covariance. A maximum likelihood approach was developed that considered correlated error relationships among measures as a way of explaining observed structures in phenotypic (co)variances. Developed procedures explained observed structures and facilitated estimation of individual variance and residual variance components.

Key Words: covariance structure • conformation traits • correlated errors

Submitted on April 25, 1990
Accepted on February 4, 1991