Preweaning body measurements of beef calves and traits of their dams as predictors of calves' postweaning and lifetime performance

Author

William Lester Brown

Date of Award

12-1969

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Animal Science

Major Professor

Robert R. Shrode

Committee Members

Charles S. Hobbs, L.M. Josephson, Robert L. Murphee, Don O. Richardson, Charles C. Trigpen

Abstract

Body measurements, body composition traits and certain performance traits of 74 Angus bull and 84 Angus heifer calves, recorded at three different observations up to weaning, were studied to assess their value as predictors of postweaning ADG, lifetime ADG (ADG from birth until the end of test), final condition scope and fat thickness (measured ultrasonically when the postweaning feeding period was terminated). n These calves were born from January 17, 1968, to April 26, 1968. A stepwise regression procedure was employed to construct prediction equations. Traits that could enter the regression equation as independent variables included heart girth, back length, loin length, rump length, total length, type score, condition score, weight and age. Also, fat thickness measured ultrasonically over the twelfth and thirteenth ribs at weaning was considered among the independent variables.

Coefficients of multiple determination (R²) for the equations to predict the dependent variables tended to be larger when the independent variables were the calves' weaning traits rather than preweaning or interim traits. It was concluded that if the dependent variables are to be predicted from calf traits observed at only one time of observation, that observation should be taken at an average age of about 220 to 225 days (weaning). Various combinations of the weaning body measurements and body composition traits explained significantly (P < .05) more variation in postweaning ADG, lifetime ADG, final condition score and final fat thickness than was explained by weight and age alone. For bulls, the increases in R² were 0.239, 0.113, 0.155, and 0.207, respectively, for the dependent variables enumerated above. In the case of heifers, the increases in R² were 0.277, 0.089, 0.105, and 0.1A6, respectively. Hence, it appears from these results that body dimension measurements and estimates of fatness can be used effectively to improve the predict tion of calf performance and subsequent body composition over conventional methods utilizing only calf weight and age.

The addition of traits of the dam (weight and condition score and linear, squared and cubed forms of change in weight and condition of the dam from April, 1968, until time of observation of calf) to the regression equations, after entering the calf traits, generally did not result in significant increases in the R² values for predicting postweaning and lifetime ADG. These cow variables tended to be slightly more important as predictors of final condition score and fat thickness of the calves. It is doubtful that the additional precision in predicting future performance and body composition of calves obtained by considering these traits of the dams, is large enough to warrant the extra effort and expense necessary to obtain these data.

Recommended Citation

Brown, William Lester, "Preweaning body measurements of beef calves and traits of their dams as predictors of calves' postweaning and lifetime performance. " PhD diss., University of Tennessee, 1969.
https://trace.tennessee.edu/utk_graddiss/8030