Date of Award
Master of Science
John D. Smalling, Will T. Butts, Jr., W.R. Backus
The production of the maximum pounds of beef at weaning is a subject of utmost importance to Tennessee cattlemen. They have been striving to achieve this goal mainly through increased cow size. Therefore, the objectives of this study were to determine the relationship between cow size as measured by weight, fat and body dimension and the performance of her calf.
Over a five-year period, records were obtained on 411 Angus and 328 Hereford cows and their calves. In Analysis I, included data were taken in 1967 through 1970 on each cow and her calf. These data were used to determine the relationship between cow weight corrected to a fat constant basis and calf performance. These data included weight and fat thickness of each cow taken in the fall of the year and weight and fat thickness for each calf at weaning and at one year of age. Analysis II included data taken in 1969 through 1971. A weight and fat thickness was obtained for each cow and calf in the same manner as in Analysis I, and four body measurements (depth, length, wither height and hook height) were taken on each cow and her calf at weaning. In this analysis year, weaning age, cow age, cow weight and cow fat were held constant in order to determine the relationship between cow size (body measurements) and calf size and performance.
In Analysis I, cow weight was found to have a positive, non-significant effect on weaning weight per 100 lb. increase in cow weight ranged from 7.3 to 12.2 lb. while the increase in cow weight ranged from 2.6 to 25.2 lb. Cow fat was found to significantly affect the weaning weight of bull calves but not the weaning weight of heifers. This relationship between cow fat and weaning weight was negative. A similar trend was found in the relationship between cow fat and yearling weight.
In Analysis II, cow body measurements were, generally, found to have no significant effect on weaning weight. Cow body length and body depth had no significant effect on weaning body length or depth. Cow wither height had a significant effect on the weaning wither height of heifers, and cow hook height had a significant effect on the weaning hook height of bulls.
In this study 57.4, 84.6, 74.9 and 73.1 percent of the variation in weaning weight was explained by variation in cow weight and fatness in Hereford bulls, Angus bulls, Hereford heifers and Angus heifers, respectively. When the three linear cow measurements (length of body, depth of body and height) were added to the model, the coefficients of determination increased by 0.029, 0.033, 5.1 and 0.08 for the four breed-sex groups, respectively.
Murphey, James Farley III, "The Effect of Cow Weight , Fat Thickness and Body Measurements on the Subsequent Performance of Her Calf. " Master's Thesis, University of Tennessee, 1972.