Growth and Development Patterns of the Skeleton in Simmental and Cross Young Beef Bulls

Abstract

The age-related carcass-morphology and composition changes and the growth and development patterns of the axial and peripheral skeleton systems and the bones composing them in the Simmental and crossbred young beef bulls have been studied. In order to carry out the survey, the young bulls were divided into three groups of 15 animals each. The first (control) group included the purebred Simmental young bulls. The second (experimental) group was formed of the halfbred and crossbred young stock produced by crossbreeding between the Simmental cows and the Simmental beef bulls of German selection. The third (experimental) group was composed of the crosses of Simmental cows with Charolais bulls. The Charolais crosses had more energy for growth. Thus, their liveweights comprised 431.9, 523.4, and 620.6 kg at the ages of 12, 15, and 18 months, respectively, which were 7.8, 7.5, and 10.2% more than that in their peers of the maternal breed. The crossbred young stock in both groups was distinct for carcass morphology and composition, reaching a more advanced level of the carcass flesh-coverage mass in all the age intervals when compared that to the purebred Simmentals. The age-related changes in the absolute and relative masses of the young-bull carcass bones are caused by different intensities specific to bone growth in the axial and peripheral skeleton systems. For instance, the intensity of bone growth in the axial skeleton system tended to increase in the postnatal period, while the bone growth rates of the peripheral skeleton system decreased. Irregularity in developing the indicated skeleton systems is caused by different intensities specific to growth of certain bones and their complexes. The highest growth rate is usually typical for ribs and the vertebral column, while the slowest growth rate is most common for extremitas thoracica and extremas pelvina. The bone growth rates for the limb proximal structures generally exceed that for the distal bone structures. The age-related differences in the growth rates of certain skeleton structures can cause some changes in ratios between the linear body measurements of the young bulls.