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.