Interrelationships Between Certain Measurements of External Body Form, Internal Anatomy, and Fat Production

Abstract

Summary Correlations between butterfat production and certain measurements of external body form were calculated from data on 216 first-lactation Holstein cows in the Beltsville herd. The correlations between production and cross-section areas of chest or paunch were lower, in most cases, than those between production and other chest or paunch measurements. They were 0.18 between production and area of chest and 0.23 between production and area of paunch. Measurements most highly correlated with production were body length (0.31), height at withers (0.35), and depth of paunch (0.36). Multiple correlation coefficients between different sets of measurements and fat production did not exceed 0.40. Measurements of external and internal anatomy were studied on 146 Holstein cows that had been measured before and after slaughter. Depth of chest was significantly correlated with internal chest depth (0.69), heart weight (0.57), and lung weight (0.32); depth of paunch with liver weight (0.48), stomach weight (0.38), length of small intestines (0.31), length of large intestines (0.37), and length of total intestines (0.36). Height at withers showed significant correlations with heart weight (0.50) and lung weight (0.28); body length with heart weight (0.49) and length of intestines (0.34). Partial correlations, with empty body weight held constant, showed that the correlations between certain external and internal measurements were a result of the common association with body weight. The relationship between size of internal organs and fat production was studied on 115 Holstein cows. Correlations were significant only in the case of length of large intestines (0.29) and length of total intestines (0.25). The correlation between depth of paunch and butterfat production was partitioned into a direct component and a component contributed by the association between depth of paunch and organs of the digestive tract. The contribution of the direct path from depth of paunch to fat production amounted to at least 35% of the total correlation. The findings do not support a general supposition that correlations between external body measurements and production are a result of interrelationships with size of internal organs.