Intake, selection, digesta retention, digestion and gut fill of two coprophageous species, rabbits (Oryctolagus cuniculus) and guinea pigs (Cavia porcellus), on a hay-only diet

A colonic separation mechanism (CSM) is the prerequisite for the digestive strategy of coprophagy. Two different CSM are known in small herbivores, the 'wash-back' CSM of lagomorphs and the 'mucous-trap' CSM of rodents. Differences between these groups in their digestive pattern when fed exclusively hay were investigated in six rabbits (Oryctolagus cuniculus) and six guinea pigs (Cavia porcellus). Intake, digestibility (by total faecal collection), solute and particle mean retention times (MRT, using Co-EDTA and Cr-mordanted fibres) were measured. Rabbits selected less fibrous parts of the hay than guinea pigs, leaving orts with higher content of neutral detergent fibre [NDF; 721 ± 21 vs. 642 ± 31 g/kg dry matter (DM) in guinea pigs]. They also expressed a lower NDF digestibility (0.44 ± 0.10 vs. 0.55 ± 0.05 of total), a similar particle MRT (15 ± 3 vs. 18 ± 6 h), a longer solute MRT (51 ± 9 vs. 16 ± 4 h), and a lower calculated dry matter gut fill (19.6 ± 4.7 vs. 29.7 ± 4.1 g DM/kg body mass) than guinea pigs (p < 0.05 for each variable). These results support the assumption that the 'wash-back' CSM, exhibited in the rabbits, is more efficient in extracting bacterial matter from the colonic digesta plug than the 'mucous-trap' CSM found in the guinea pigs. Related to metabolic body mass, rabbits therefore need a less capacious colon for their CSM where a more efficient bacteria wash-out is reflected in the lower fibre digestibility. A lighter digestive tract could contribute to a peculiarity of lagomorphs: their ability to run faster than other similar-sized mammals.     

Effect of coprophagy on bioavailability of iron from plant foods fed to anemic rats

Effects of coprophagy and coprophagy preventing device on iron bioavailability were evaluated in two experiments. In Experiment 1, rats were fed diets with FeSO₄, spinach, bran cereal or cornmeal as the iron source. The rats in each diet group were fitted with collars, sham-collars or not fitted with collars (control). In Experiment 2, rats were fed diets with FeSo₄ or green peas as the iron source and were fitted with collars, tail cups, sham-collars or not fitted with any device (control). Preventing coprophagy reduced hemoglobin regeneration efficiency (HRE) of rats fed bran cereal, green peas, spinach or cornmeal diets by 26 (P<.05), 24(P<.05), 22(P<.05) and 11% (not significant), respectively. Preventing coprophagy in rats fed FeSO₄ diet did not significantly reduce HRE. Sham-collaring reduced (P<.05) HRE of rats fed the FeSO₄ diet by 12 and 13% but did not significantly affect HRE in rats fed food iron sources. It was more convenient and effective to prevent coprophagy with collars than with tail cups. Differences in bioavailability between food and FeSO₄ iron due to coprophagy may be explained based on two gastrointestinal nonheme iron pools, complexed and highly soluble.     

Digestive strategies of small hindgut fermenters

Small mammalian herbivores have a limitation in their supply system of nutrients to their energy and protein demands because they need much more energy and protein per unit body mass than larger herbivorous animals. Therefore, small herbivores need to have characteristic strategies in their digestive systems to overcome the limitation of their small body mass compared with larger animals. Although small herbivorous mammals commonly have an enlarged cecum, the pattern of flow and mixing of digesta in the large intestine varies among them. Distinct separation of the larger fiber particles from smaller and liquid contents which are retained in the cecum can be recognized in some species. Coprophagy, practiced by many small herbivores, has nutritional significance providing a source of vitamins, amino acids, and other nutrients which are excreted with feces. Among coprophagous mammals, several species produce two types of feces: soft feces, which are eaten; and hard, which are not eaten. Soft feces contain more water than hard feces and dry matter includes more protein and less fiber. Coprophagic behavior must be supported by the colonic separation mechanism, which operates retrograde transport of fluid and fine particle digesta or bacteria trapped in the mucus, resulting in high density bacteria in the cecum contents, which is successively consumed as cecotroph. These mechanisms must be necessary for small herbivores to survive on the feed in their habitat.     

Investigation on the growth of coprophagy-prevented rats with supplemented vitamin B12

The growth of coprophagy-prevented rats was compared under administration of normal levels of vitamin B12 and supplemented amounts. Two experiments in which supplemented amounts of vitamin B12 were administered were conducted under different conditions. Six rats per group were fed under coprophagy-allowed (conventional feeding) and coprophagy-prevented conditions respectively. In the first experiment, coprophagy-prevented rats were fed only feed containing recommended vitamin B12 level and forced fed hydrous faeces, vitamin B12 and folic acid respectively. In the second experiment, coprophagy-prevented rats were fed AIN-93G at the recommended vitamin B12 level (25 microg/kg diet), at 100 times the level and at 1000 times the level respectively. Body weight, feed consumption and amounts of each faeces type were determined in both experiments. In a comparison of body weight gain, we learned that coprophagy prevention reduced the values, but that there was no significant difference in the forced feeding group in the first experiment. Similar results were recognized in the second experiment. Vitamin B12 supplementation was not able to raise feed intake significantly and hence it obviously was not a severely limiting factor under the respective experimental condition which depressed feed intake.