Factors Affecting Efficiency to Weaning in Angus, Charolais, and Reciprocal Cross Cows

The purpose of this study was to gain understanding of the variables affecting efficiency of cows and production of their calves to weaning. Specific effects of cow size, condition and milk production on efficiency were examined along with reproductive performance of the experimental females to determine net weaning efficiency. An attempt was also made to examine traits that could be used in practical situations to detect differences in cow efficiency. Considerable research has been conducted to evaluate post weaning efficiency of nutrient utilization, but due to expense and time requirements individual feeding of cows and their progeny has been limited. Methods employed to individually feed cows in drylot have been feeding according to metabolic weight (Klosterman et al., 1974; Turner et al., 1974), feeding to maintain equal fatness by visual appraisal (Carpenter et al., 1974) and feeding low energy rations ad libitum (Kress et al., 1969; Onks et al., 1974). Various problems have been encountered with use of such methods. In the projects reported here, an attempt was made to simulate pasture nutrition levels in the feeding of drylot cows