The effects of intial body size on feeder calves on subsequent performance

The effects of the initial body measurements of length, wither height, rump length and depth plus fat thickness on certain subsequent performance traits of feeder calves were tested to assess their value as predictors of gain and carcass value. Stepwise regression equations were employed to determine prediction equations where initial weight, fat thickness, depth of body, length of body, height at withers, and length of rump would enter as independent variables. They were interim ADG's, first through the fifth month of the feeding period, final ADG, days on feed, final slaughter grade, final fat thickness, and carcass grade. The results of the study were as follows: 1. During the interim period, R² values for prediction equations were low, and initial traits were inconsistent in the control of variation in gains; although height at withers and body length tended to account for a larger amount than the other traits. Height at withers was most important in predicting gain during the first and third months of test, while length of body was most influential in controlling variation in gain during the fourth month. R² values for ADG for the second month were extremely low, possibly due to variation in weights caused by "fill." 2. Final ADG was affected most by wither height, length of body and weight, accounting for for 11.8, 2.1, and 1.5 percent of the variation, respectively. 3. Initial weight, fat thickness and depth contributed most in reducing sums of squares for days of feed with R² values of 0.210, 0.078, and 0.013, respectively. 4. Final slaughter grade was influenced most by initial depth and height at withers, both contributing 2.1 percent to the explained variation, which was far more important than the other independent variables. 5. Initial fat thickness and weight accounted for lid and 2.8 percent of variation in final fat thickness, respectively. From these equations, it appears that initial linear measurements along with weight and fat thickness had very little effect on subsequent feedlot performance with the possible exception of days on feed, which accounted for 31.0 percent of the total variation. Length of rump was of no importance in predicting any of the traits; although it tended to be related to final fat thickness more than height at withers and length of body. As a result this measurement could possibly be eliminated in future studies, based on the findings of this analysis.