Search

Changes in coprophagy with age were investigated in male ICR mice during their life span. Sucklings showed coprophagy at 17 to 18 days old, i.e., a few days after they began to excrete feces autonomously. The number of fecal pellets ingested peaked at 5 to 6 weeks old (13 pellets/day) and gradually decreased, thereafter (2.1 pellets at 78 weeks old, 1.5 pellets at 104 weeks old). The diurnal pattern of coprophagy also changed with age. Growing mice showed vigorous coprophagous activity in both light and dark phases, whereas animals over 30 weeks old exhibited less activity in both phases, especially in the dark phase. Feces proved to be abundant in vitamin B12 and folic acid throughout the life span. These results suggest that the frequency of coprophagy changes in association with the nutritional requirements of mice during the process of growth or aging.

Coprophagy was observed in germfree (GF) ICR mice of both sexes, and the results were compared with those of conventional mice. Frequency of coprophagy per animal per day in GF mice was 5.1 in males and 5.8 in females. In conventional (CV) mice, the frequencies were 6.2 in males and 5.3 in females (data from Zoological Science 2:249-255, 1985), with no significant differences compared with GF mice. Coprophagy in CV mice was frequently observed during 6-8 hr after lighting, whereas such close time relationships tended to weaken in GF animals. In a comparison of levels of constituents per unit weight between feces and diet, fecal crude protein and crude fat exhibited lower values than those in the diet. Levels of fecal crude ash and crude fiber were higher than those in the diet, and nitrogen-free extract was almost equal to that in the diet. No essential difference in these tendencies was found compared with CV mice. Levels of fecal vitamin B1, B2, B12 and folic acid were lower than those in the diet. In CV mice, except for vitamin B1, these vitamins exhibited either almost equal or much higher levels compared with those in the diet (data from Experimental Animals 35: 381-386, 1986). From the fact that coprophagy was observed in GF mice, it is suggested that the behavior is inherent in the mouse.