Relationship between production performance, visual appraisal and body measurements of young Dorper rams

The body measurements of 433 young Dorper rams participating in the Free State and Northern Cape veld-ram projects were correlated with their production performance. These measurements included a selection index, body weight (kg), average daily gain (g/day) and scrotal circumference (cm). The performance of the animals in the two projects compared well, although the means in the Free State project were slightly higher. A high phenotypic correlation (0.80) was found between heart girth (cm) and body weight (kg) and a correlation of 0.76–0.79 was found between body length and body weight. Heart girth had the most significant influence on all growth parameters. Shoulder height, which is regarded as a good indicator of frame size, had medium correlation (0.55–0.58) with body weight and low-medium (0.28–0.36) correlation with selection index. The later maturing animals do not, therefore, necessarily perform better than the early maturing ones. Low correlations (0.04–0.11) were found between coat type and the selection index and between masculinity (0.27–0.28) and selection index. The correlation between canon bone circumference and the selection index (0.41–0.45) was higher than the correlation (0.23–0.33) between canon bone circumference and canon bone length. Scrotal circumference had low to medium correlations with growth parameters.