Principal gastrointestinal variables associated with metabolic heat production in pigs: statistical cluster analyses

The purpose of this study was to classify organs/tissues into clusters according to their association with fasting heat production (FHP) by multivariate cluster analysis and to identify primary tissues. A data set consisting of 47 variables and 2256 data points was collected from 48 growing male pigs. Variance was perturbed by varying the daily feed allowance. Cluster analysis was conducted at each of six levels of body dissections, and a final analysis was conducted with all 47 variables. Small intestine, pancreas, liver, and kidneys were consistently assigned to the FHP-cluster; stomach, cecum, and colon to clusters correlated, r greater than 0.5, to the FHP-cluster; carcass, thoracic and offal variables to unrelated clusters. In the final analysis with all 47 variables represented, only variables from the small intestine and jejunum were assigned to the FHP-cluster. It is concluded that the small intestine, which accounts for only 2% of the body weight, is a primal organ system in swine and that pancreas, liver, and kidneys are of similar importance.