Doctoral Dissertations

Date of Award

12-1982

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Animal Science

Major Professor

Robert R. Shrode

Committee Members

J.B. McLaren, H.V. Shirley, D.R. West

Abstract

To assess the relative influences of sex linkage and maternal effects, sire-son, sire-daughter, dam-son, and dam-daughter correlations of Birth Weight and weaning and post-weaning (to a year of age) Body Weight, Gain, Average Daily Gain, Heart Girth, Body Length, Hip Width, Hip Height, Fat Thickness, Type Score, Condition Score, and Frame Score of 1903 Angus calves and 1126 Polled Hereford calves were calculated after least-squares adjustment to remove variation in weaning and post-weaning traits due to differences in age of dam and age of calf. Sex-linkage effects appear to be important in Weaning Body Weight, Weaning Gain, Weaning Average Daily Gain, Post-Weaning Weight, Life-Time Average Daily Gain, Post-Weaning Heart Girth, and Post-Weaning Hip Width in Angus. None of the traits seem to show any important sex-linkage effect in Polled Herefords. Maternal effects appear to be important only in Post- Weaning Body Length in Angus and Weaning Fat Thickness, Post- Weaning Weight, Life-Time Average Daily Gain, Post-Weaning Type Score, and Post-Weaning Condition Score in Polled Herefords. Sex-linkage and/or maternal effects are appreciable in Weaning Weight, Weaning Gain, Weaning Average Daily Gain, Weaning Heart Girth, Weaning Body Length, Post-Weaning Weight, and Life-Time Average Daily Gain in Angus. However, in Polled Herefords, sexlinkage and/or maternal effects together are important in Birth Weight, Weaning Hip Width, Weaning Fat Thickness and Post-Weaning Type Score. Sex linkage and sex linkage confounded with maternal effects as one value appear to be greater in Angus than in Polled Herefords with respect to the majority of the traits while maternal effects appear to be greater in Polled Herefords than in Angus with respect to most of the traits. The majority of the assessments decrease in both breeds between weaning and post-weaning with respect to sex-linkage effects, maternal effects, and sex-linkage and/or maternal effects with some differences between the two breeds, possibly due to the fact that Angus are earlier maturing than Polled Herefords in both sexes, and the heritability of rate of maturing in Angus appears, from research of others, to be more than twice that in Polled Herefords.

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