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Four rats were housed in cages with mesh floors; another four rats were housed in tubular anti-coprophagy cages, in which they could not turn round to reach their own faeces. Both groups were fed for 6 d on a low-protein diet containing fermentable carbohydrates and 15NH4Cl. At the end of the experiment the rats were killed and their carcasses were homogenized, lysine was isolated by ion-exchange chromatography and its 15N enrichment measured by isotope-ratio mass spectrometry. The 15N enrichment in the lysine of the microbial fraction of faeces and the total amount of lysine in the body were also determined in order to estimate the amount of microbial lysine absorbed. The 15N enrichment in body lysine of non-coprophagic rats was not different from that previously measured in rats given unlabelled NH4Cl, but in coprophagic rats it was significantly higher. The daily absorption of microbial lysine by the coprophagic rats accounted for 20·7 (SE 2·55) mg/kg body weight0·75 but was only 0·5 (SE 1·04) mg/kg body weight0·75 for the non-coprophagic rats. This value was not significantly different from zero. The utilization of microbial amino acids via coprophagy resulted in a higher weight gain (adjusted for intake) in the coprophagic group (15·5 g/6 d) than in the non-coprophagic rats (3·1 g/6 d). It was concluded that, in rats, the utilization of microbial lysine occurred exclusively via coprophagy.

sWe developed a new type of anal cup for prevention of coprophagy and determined whether the absorption of Ca and Mg and the stimulatory effects of feeding fructo-oligosaccharides (FO) on theabsorption of Ca and Mg were altered by prevention of coprophagy in rats. Rats were fed on a FO-free diet or a diet containing 50 g FO/kg for 2 weeks with or without prevention of coprophagy. FO-feeding increased the apparent absorptive ratio of Ca and Mg in rats with or without prevention of coprophagy. However, in the FO-fed groups the absorptive ratio of Mg in rats with prevention of coprophagy was higher than in rats withont prevention of coprophagy. The Ca content of the femur was higher in rats fed on the FO-diet than in rats fed on the FO-free diet both with and without coprophagy. In conclusion, FO-feeding increased the absorption of Ca and Mg in rats both with and without coprophagy. Moreover, prevention of coprophagy enhanced the absorption of Mg in rats fed with FO. Coprophagy has to be considered when the effects of luminal fermentation or mineral absorption are examined in rats

Male rats were fed on either a non-purified rodent diet (JS) or cholesterol-free purified diets containing wheat bran (WB) or oat bran (OB). Some animals were allowed normal access to their faeces for coprophagy (coprophagy +), while in others coprophagy was prevented by placement of a plastic cup over the anus (coprophagy −). Direct ingestion of faeces from the anus was observed in the former groups. Food intake was unaffected by diet or coprophagy status and body weight gain was unchanged with OB − and JS − but was significantly lower with WB −. Plasma cholesterol was highest with WB and equally lower with OB and JS and was unaffected by coprophagy status. Plasma triacylglycerols were highest with OB and were unaffected by coprophagy status. Caecal digesta mass was highest with JS, intermediate with OB and lowest with WB. Digesta mass was unaffected by coprophagy status with WB and JS but was higher with OB −. Digesta moisture content was lowest with WB + but highest with WB −. Digesta volatile fatty acid (VFA) concentrations were similarly lower with OB + and OB −, but were significantly lower with JS − and WB − than in the corresponding coprophagy + group. In all groups digesta butyrate concentrations were reduced by coprophagy prevention. Pools of total VFA, acetate and butyrate in the digesta were highest with JS. Pools of total VFA in digesta were highest with JS +, OB + and OB − and lowest with WB + and WB −. The propionate pool was highest with OB −, intermediate with OB +, and equally low in all other groups. The pool of butyrate was highest with JS + and lowest with OB −. Effects of oats and wheat on plasma cholesterol in the rat do not seem to be mediated through faecal re-ingestion.

The quantity of re-ingested faeces was calculated by comparing faecal dry matter of unrestricted rats and coprophagy-restricted rats after correcting for differences in food intake. Due to high day-to-day variations of produced and re-ingested faeces it was not possible to calculate precisely the extent of coprophagy of an individual rat at a particular day with this difference method. Reliable quantitative estimates require at least two rats and a collection period of 7 d. When fed on a nutritionally complete diet, rats re-ingested 0-11 % of their faeces. When fed on low-protein diets (66 g egg albumin/kg) or diets diluted with 200 g cellulose/kg, coprophagy was not significantly increased. A high re-ingestion rate (6–25 %) was observed with thiamin and pantothenic acid deficiencies. After re-ingestion of faeces had been prevented for 1 week, the amount of faeces re-ingested during the subsequent week without tail-cups was increased twofold. It is concluded that rats are able to regulate the amount of faeces eaten precisely according to their requirements.

1. Refection, resulting in an increased supply of riboflavin to riboflavin-deficient rats through coprophagy, was demonstrated on a sucrose-based diet when sensitive biochemical tests of riboflavin status were employed: these included measurements of NAD(P)H2:glutathione oxidoreductase (EC1.6.4.2); succinate:(acceptor) oxidoreductase (EC1.3.99.1) and NADH:(acceptor) oxidoreductase (EC1.6.99.3).2. The use of tail-cups to eliminate coprophagy, and hence refection, resulted in a more rapid and reproducible progress into severe deficiency.3. The occurrence of refection on a sucrose-based diet may account for hitherto unexplained differences between previous publications on the biochemical effects of riboflavin deficiency.

1. The abilities of cattle, sheep, goats, equines and rabbits to digest mature timothy (Phleum pratense) hay were compared. Apparent digestibilities were partitioned into true digestibility, metabolic faecal output (MFO) and fibre digestibility. The aim of the study was to determine the relative effects of fermentation site (among groups) and of body-weight (within groups) on the efficiency of digestion.2. The ruminants were superior to equines, which were in turn superior to rabbits, in digesting fibre components of the hay. A large individual variation in digestibility was noted only for the equines. Increasing body-weight was associated with higher digestibility in ruminants, but no such trends were seen in the non-ruminants.3. The MFO expressed as a proportion of dry matter intake gave similar values for all groups (0·085–0·118). As a proportion of available microbial substrate originating from the feed, the values were found to be 0·167 for the ruminant, 0·425 for the equines and 2·13 for the rabbits. The value for the rabbits shows that their lower tract microflora must obtain energy from non-fibre components of the feed. No appreciable digestion of the generated microbes by the host was suggested by the values obtained for the equines.

1. Two sows were housed in farrowing crates with slotted floors and fed daily with approximately 200 μCi 198Au from 3 d before farrowing until their piglets were 21 d old.2. The sows' faeces became radioactive but their milk remained free of radioactivity. The piglets' mean (±SE) whole-body radioactivity was equivalent to 8·5 ± 0·9 g (range 3·8–15·5 g) of faeces. This is probably a measure of their daily intake of faeces.3. The possibility of using this natural coprophagia to prevent piglet anaemia has been demonstrated on two commercial piggeries by feeding the sows a diet containing 2000 mg Fe/kg.