Masters Theses

Date of Award

8-1978

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Science

Major Professor

Will T. Butts, Jr.

Committee Members

J. W. Holloway, E. W. Swanson

Abstract

Data from 391 Hereford feeder heifers were utilized to study the relationship among objective body measurements, sale weight, subjective scores, subsequent performance, and carcass traits. The animals were also used to compare variance of carcass and performance traits of animals lotted into similar groups on the basis of weight and grade or multivariate indexes utilizing objective body measurements. Calves were fed a silage plus limited concentrate or a standard growing-finishing ration depending on their respective year-allotment system group. Pens of heifers were slaughtered when the mean fat thickness of the heifers within a pen (6 animals per pen) reached 12 millimeters. The heifers were photographed, weighed, and sonorayed for subcutaneous fat thickness upon arrival at the farm. These data along with the weight of the heifers at the time of purchase mads up objective measurements. Subjective scores were obtained from the evaluation of the animals by a single grader before the initiation of the test. These data made up the variables which were used in the two sets of prediction equations, Predictions of performance and carcass traits made by utilizing sale weight and the objective or subjective scores revealed that the amount of variation explained in the dependent variables was similar for the objective measurements or the subjective scores. The objective scores consistently explained a slightly higher amount of variation due to the inability of estimated backfat to replace the variation explained by somoscoped backfat. These prediction equations were adjusted for the mean carcass fat to reduce the variation introduced by selling the animals on a pen mean backfat basis. Comparison of the variances in carcass and performance traits of cattle lotted by weight and grade versus multivariate indexes revealed that the indexes were successful in reducing the variation in fat-related traits but not in carcass quality grade or final weight. Variation in the fat-related carcass and performance for the silage-limited concentrate ration group was reduced, and variation for this group was greater for final weight and carcass quality. All traits showed consistently less variation in 1972 than in 1973.

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