External form and internal anatomy of Holsteins and Jerseys

Body weights, external dimensions, and postmortem measures of internal body dimensions or weights of organs and glands of Holsteins and Jerseys were used to establish norms, interrelationships of traits, and effects of sire and inbreeding on changes in external form. Sires differed in nearly all measures of external body form. Sire effects increased with advancing age whereas effects of inbreeding (greater than 12.5, 3.0 to 12.4, or less than 3.0% of inbreeding) declined. Skeletal dimensions were smallest in the greater than 12.5% inbred group. Differences due to inbreeding were largest at 3 and 6 mo of age and in first lactation. Body heights and head dimensions were nearer to mature size at 3 and 6 mo than other measures. In both breeds, most rapid development was between 3 and 6 mo, but Jersey matured 1 to 2% faster. Age (2 to 3, 4 to 5, 6 to 10, greater than 10 yr) was significant for most postmortem measurements. Correlations among measures of external form were .30 to .93. Correlations between external form and internal features or between internal dimensions and organs were lower. External and internal features were positively correlated, but few external features showed strong enough association with internal features for use as predictors of size of organs, glands, or digestive capacity.