Growth of the Parts of the Alimentary Tract of the Rat, and the Small Intestine of the Sheep, Relative to Growth in Live Weight.

Abstract

The dry weight of stomach, small intestine, caecum and colon was obtained from male and female rats from 8 to 184 days old weighing from 18 to 400 g. The length of the colon and small intestine was also measured. The length and dry weight of the small intestine of 35 merino sheep from birth to aged or 3 to 40 kg liveweight were also measured. Regressions between the logarithms of gut measurements and logarithms of the liveweights were calculated. The gut measurements were length, length/kg liveweight, DM, DM/kg liveweight and DM/m for the tubular small intestine and colon, and DM and DM/kg liveweight for the saccular stomach and caecum. For the rat, 2 relations were required to describe the data from all organs. A change in percentage increase or decrease relative to percentage liveweight increase occurred at about 70 to 80 g liveweight or 37 to 44 days old. This is the age range at which increase in metabolic rate relative to liveweight declines to about one-quarter of its previous rate. It is unlikely that there is a causal relation between the maturation of sex hormone output and gut growth and metabolic rate. One allometric regression coefficient adequately described growth of the small intestine of the sheep relative to weight gain.