Specific heat output (SHO) of visceral organs/tissues: the hypothesis and first estimations

It was hypothesized that each organ/tissue has a characteristic specific heat output (SHO; kcal/d.g). Heat output (HO; kcal/d) is defined as the product of the SHO and the weight, g, of the organ/tissue. FHP (fasting heat production) is defined as the sum of HO values of all tissues of fasted animals. FHP and organ weight were perturbed by variations of food intake of 48 young swine before FHP and weights of 36 organ/tissue variables were measured. Cluster analysis was used to group the variables and simplify the analyses and indicated that small intestine, kidneys, liver and pancreas were principal sources of FHP. Regression estimates indicated that the SHO of pancreas and kidneys was high (1.1 to 1.9), that of small intestine, liver and colon was intermediate (.21 to .26), and that of stomach and lungs was low (.11 to .14). All other viscera tissues were assumed to have SHO near that for nonviscera, estimated at .0165 kcal/d.g. Mean values of FHP and empty body weight were 1856 kcal/d and 46,651 g respectively; thus the mean SHO value of all tissues was about .04 kcal/d.g. The SHO values of stomach, intestine, colon, pancreas, kidneys, liver and lungs were in the range 3- to 50-fold greater than SHO of the whole body and in the range 7- to 120-fold greater than the estimated SHO of the nonviscera. These findings indicate that the small intestine, liver and kidneys account for about 60% of HO from viscera or about 30% of total FHP.