Date of Award
Master of Science
Haley M. Jamison
Robert R. Shrode, Robert S. Dotson
The performance records of 1,534 non-creep fed, purebred Angus heifer and bull calves born during the months of January, February, March and April at Ames Plantation were utilized in this study. These data were collected over a 12-year period (1957-68). Two of the traits of economic importance in Tennessee, average daily gain from birth to weaning and type score at weaning, along with condition grade were studied in these analyses. The objective of this study was to evaluate the influence of sex of calf, age of dam, and month of birth on these traits and to propose adjustment factors to remove from the variables as much as possible of the influence of certain of these environmental effects. Analyses were conducted on all of the data and on data from the first half and last half of the 12-year period. In all analyses, sex of calf had a significant effect (P < .01) on average daily gain from birth to weaning. Male calves gained an average of 0.18 pounds per day more than female calves. The effects of sex of calf on type score were non-significant in some analyses, but in two analyses male calves graded 0.52 and 1,10 points, respectively, higher than female calves. The data indicated also that heifer calves, on the average, had condition grades that were one-third of a grade higher than male calves. Month of birth had no significant effect on average daily gain to weaning. However, the month the calf was born did haye a significant effect (P < .05) on type score in one analysis. The effect of month of birth on condition grade was significant (P < .05) in only one analysis. In all but one analysis age of dam was found to have a highly significant effect on average daily gain from birth to weaning. These data show that a cow's individual performance was lowest at 2, 3, 4 and 12 years of age. In all but one analysis age of dam had a highly significant effect on type score. These data indicate that the maximum type score of a cow's calves was attained when she was within the age range of 3 to 9 years and decreased as she became older. The effects of age of dam on condition grade were significant. Calves of 5- and 6-year-old cows had a higher condition grade than calves of cows of other age groups. While weaning age had a significant (P < .01) effect on average daily gain to weaning, it did not have a significant effect on type score. The relationship between weaning age and type score was negative in three analyses, indicating that as calves became older, the type scores were lower. Weaning age had a significant (P < .01) effect on condition grade in only one analysis. Since the linear relationships in all analyses were positive, one would conclude that as the calf became older than the mean age the condition grade would be higher. The effects of condition grade on type score was significant in only two analyses. The correlation between condition grade and type score was 0.52. This was the highest correlation of any combination of traits studied. In all analyses, condition grade as a continuous variable had a significant (P < .01) positive effect on average daily gain from birth to weaning. On the basis of the amount of variation accounted for and the time of collection of the data used in each analysis, the analyses of the last six years' data were chosen as the appropriate ones on which to base the calculation of additive least-squares adjustments for the effects of sex, month-of-birth and age of dam.
McKee, James Wayne, "Factors affecting variation in the production of beef cattle at Ames Plantation. " Master's Thesis, University of Tennessee, 1970.