Parameters to describe the growth of male cattle

Abstract

Parameters were estimated for nonlinear growth curves for bulls of five straightbred and 20 crossbred breedtypes produced in two generations of a diallel. The primary intent of this study was to use the estimates obtained for mature size and maturing rate to define male growth in a manner that would be appropriate for use in the Texas Agricultural Experiment Station Beef Cattle Simulation Model. To compensate for potential changes in the model structure and past problems encountered in previous applications of that model, dry matter intake was also examined for female contemporaries of those bulls. The results that were obtained from the nonlinear regressions made on the male growth data indicated that the determination of mature size for males in the model was appropriate, but a discrepancy was indicated for the determination of maturing rate. The magnitude of that discrepancy suggested that it may have arisen due to the drastically different environment imposed on the males relative to their female counterparts. That condition prohibits the direct application of the results of this study to the model. However, such an application can be made when information relating to the composition of these bulls becomes available. Reformulation of the restrictions to intake in the model was achieved through the evaluation of dry matter consumption of the female contemporaries. A comparison with an independent data set indicated that the reformulation was justified. The benefits of that change are that the time required for validations of the model can be reduced and that the descriptive properties of the model have been enhanced.