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Integration of microbiota in a host begins at birth and progresses during adolescence, forming a multidirectional system of physiological interactions. Here, we present an instantaneous effect of natural, bacterial gut colonization on the acceleration of longitudinal and radial bone growth in germ-free born, 7-wk-old male rats. Changes in bone mass and structure were analyzed after 10 days following the onset of colonization through cohousing with conventional rats and revealed unprecedented acceleration of bone accrual in cortical and trabecular compartments, increased bone tissue mineral density, improved proliferation and hypertrophy of growth plate chondrocytes, bone lengthening, and preferential deposition of periosteal bone in the tibia diaphysis. In addition, the number of small in size adipocytes increased, whereas the number of megakaryocytes decreased, in the bone marrow of conventionalized germ-free rats indicating that not only bone mass but also bone marrow environment is under control of gut microbiota signaling. The changes in bone status paralleled with a positive shift in microbiota composition toward short-chain fatty acids (SCFA)-producing microbes and a considerable increase in cecal SCFA concentrations, specifically butyrate. Furthermore, reconstitution of the host holobiont increased hepatic expression of IGF-1 and its circulating levels. Elevated serum levels of 25-hydroxy vitamin D and alkaline phosphatase pointed toward an active process of bone formation. The acute stimulatory effect on bone growth occurred independently of body mass increase. Overall, the presented model of conventionalized germ-free rats could be used to study microbiota-based therapeutics for combatting dysbiosis-related bone disorders.

Guinea pigs are assumed to practice caecotrophy to a higher degree than rats. Studies from leporids suggest that through the practice of caecotrophy, hindgut fermenting species could build up microbial fatty acids (FA) in body tissues. We hypothesized that microbial FA would be detectable in the body tissue of guinea pigs and rats, and this to a higher degree in guinea pigs. Twenty-four rats and guinea pigs were fed with four different pelleted diets (lucerne-, meat-, meat-bone-, insect-based) in groups of six animals for 8 weeks. Perirenal adipose tissue differed in FA composition between the species in spite of the common diets. FA typically associated with microbial activity (saturated FA (SFA; typically 18:0), monounsaturated FA (MUFA; typically trans-fatty acids TFA), and odd- and branched-chain FA (Iso-FA)), were all detected. Guinea pigs had higher SFA levels than rats except on the lucerne diet. Concentrations of 18:0 were higher for guinea pigs on the meat and bone diet. Iso-FA concentrations in guinea pigs exceeded those of rats on all diets. FA profiles with a microbial fingerprint appear-although in low proportions-in the body tissue of both species, and this seemingly to a higher extent in guinea pigs. With respect to whether consumption of rodent meat rich in microbial FA has particular effects on human health as shown for ruminant products, microbial FA concentrations are probably too low to cause any distinct effects.

A behavioural animal model of faecal continence and/or incontinence would be of value in experimental studies of the mechanisms by which sacral neuromodulation can effect continence mechanisms in humans. The aim of this behavioural study was to establish whether the rat, an obligate coprophagic species, exhibits patterns of faecal continence. Standard rat cages were modified to consist of a food and drink area, a nesting area and an empty latrine area. Three floor pressure pads were connected to hour meters to record the time spent in each area over the course of 4 days. The door to the latrine was open for 2 days and closed for another 2 days to create a physical barrier that could only be surmounted by climbing over a partition. In the first 2 days, most faecal pellets (74 ± 20 %; p

A sensitive and reliable biomarker has yet to be identified for marginal copper deficiency in humans. The need for such a biomarker is critical, because increased cases of human copper deficiency evolve following bariatric surgery and other secondary factors besides diet. Four experiments were devised to induce marginal copper deficiency through copperdeficient (CuD) diets (5 wk for mice and 4 wk for rats). In Expt. 1 and 2, male postweanling mice were raised in either solidbottom plastic cages (Expt. 1) or stainless steel hanging cages (Expt. 2) and compared. Postweanling rats (Expt. 3) and adult mice (Expt. 4) were also studied using stainless steel cages. Copper-adequate controls were fed a semipurified diet containing 9 mg Cu/kg. CuD rats exhibited the most severe changes in biomarkers due to copper limitation, including major reductions in plasma ceruloplasmin (Cp) and erythrocyte superoxide dismutase (Sod1) and augmentation in copper chaperone for Sod1 (CCS). The CuD mice in Expt. 2 were more deficient than the CuD mice in Expt. 1, likely due to coprophagia differences. In fact, the CuD mice in Expt. 1 had unaltered Sod1 or Cp levels. Importantly though, these marginally deficient mice and CuD adult mice that had no changes in Cp activity or liver copper level had robust augmentation of CCS. Erythrocyte CCS was the only consistent biomarker to change in copper deficiency for all dietary groups, suggesting that CCS may be an excellent biomarker for human confirmation of marginal copper deficiency. J. Nutr. doi: 10.3945/jn.111.150755.

Amino acid, mineral and vitamin levels in hydrous faeces obtained from coprophagy-prevented rats were examined. Two experiments were conducted with rats of different age, 4 weeks and 10 weeks. Six rats each were fed under coprophagy-prevented and coprophagy-allowed (conventional feeding) conditions, respectively. In the first experiment using 4-week-old rats, amino acid values were determined for hydrous faeces and usual faeces obtained in the above-mentioned conditions. In the second experiment using 10-week-old rats, mineral values were determined for both types of faeces. Vitamin values were determined in both experiments. In a comparison of amino acid values and their patterns, specific kinds of amino acids in hydrous faeces were not recognized as growth factors. Sodium and potassium levels in hydrous faeces were significantly higher than those for usual faeces, but those levels were 1/(18-20) of those derived from feed. Although cyanocobalamin and folic acid levels in hydrous faeces were two to three times higher than those for usual faeces, folic acid supplements from coprophagy were 1/8 of those derived from feed. Cyanocobalamin supplements from hydrous faeces were five times larger than those from feed. Therefore, it appears that cyanocobalamin was supplied by the ingestion of hydrous faeces and that this cyanocobalamin supports conventional growth in rats.

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.

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 less than .05), 24(P less than .05), 22(P less than .05) and 11% (not significant), respectively. Preventing coprophagy in rats fed FeSO4 diet did not significantly reduce HRE. Sham-collaring reduced (P less than .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.

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.

Starvation potentiates the hepatotoxicity of a variety of small molecules, including chlorinated hydrocarbons and nitrosamines, through the induction of CYP2E1. A change in CYP2E1 expression during starvation may also alter the pharmacokinetic profiles of xenobiotics. Northern blot and Western blot analyses revealed that hepatic CYP2E1 was not induced during starvation in rats placed in metabolic or wire-bottom cages in contrast to the induction of CYP2E1 in animals housed in solid-bottom cages. We studied the effect of coprophagy on the expression of hepatic CYP2E1 during starvation. The extent of coprophagy was 24% in fed rats. Fecal matter of starving rats was reduced to 14% of control and starving rats re-ingested ~1.6 g of feces per day. The effect of fecal matter on CYP2E1 expression (i.e., 1.6 g/kg/day for 3 days) was assessed in fed or starving rats. Starving rats gavaged with fecal matter for 3 days resulted in a 3.5-fold increase in the level of CYP2E1 mRNA, while fed rats gavaged with feces failed to show an increase in the mRNA. The increase in the CYP2E1 mRNA level accompanied the induction of CYP2E1. Starving rats gavaged with methanol extract of feces (500 mg/kg/day for 3 days) showed a 3.3-fold increase in CYP2E1 mRNA level in the liver. These results provide evidence that CYP2E1 is not induced by starvation without coprophagy, raising the contention that the mechanistic basis for CYP2E1 induction by starvation should be reevaluated.

Coprophagy can be minimized by fitting rat cages with metal grids which allow faecal pellets to pass through to the floor of the cage. When bedding was omitted overnight, the extent of coprophagy could be estimated from the weight of the droppings on the cage floor or the weight of the gastrointestinal (GI) tract removed from rats housed with or without grids. The effect of coprophagy was also demonstrated by the elevation of serum urea nitrogen in rats that consumed faeces. Therefore, precautions against coprophagy, or their absence, should be specified in all experimental protocols and reports.

Four diets were prepared in which cooked potatoes provided approximately 0.8 of the dry matter (DM) and all the polysaccharides. The potatoes were either boiled conventionally (unprocessed) or prepared by rehydrating a commercial ‘instant’ potato product with boiling water. The diets were fed to rats (six per diet) immediately after preparation or after storage at 4° for 48 h and observations made on site and extent of digestion and large bowel (LB) fermentation. All diets were equally well digested (overall means 0.95 and 0.96 for DM and organic matter (OM) respectively) with a significant proportion of this digestion occurring in the LB. More OM flowed to the LB with the ‘instant’ (0.18 of intake) than with the unprocessed potato diets (0.13 of intake) and was associated with markedly different fermentation patterns. When compared with rats fed on the unprocessed potato diets, those given ‘instant’ potatoes had smaller caecums with much shorter transit times, lower caecal pH, higher total volatile fatty acid (VFA) concentrations and a greater molar proportion of butyrate in these VFA. Storage of the diets for 48 h at 4° had relatively smaller effects on these variables. Possible mechanisms for the observed effects and implications for tissue metabolism and health are discussed. In addition, a simple and apparently novel method for quantifying coprophagy is proposed.

Previous fecal collection cups with tape fixation frequently led to serious necroses of the rat tail due to strangulations, and did not allow for growth of the tail. A recently developed new model gives space for rapidly growing tails and is securely fixed by a cannula perforating both fecal collection cup and tail. It is transparent, cheap to be made, and easy to empty and was tested in 118 animals for two and four weeks. In no case the cup did loosen or had to be removed due to infections, strangulations or any local problems.

Male rats which ingest feces of lactating females produce anal excreta which is attractive to pups. This excreta is as attractive as that of lactating females and more attractive than the excreta of males eating a diet of lab chow only. Anal excreta of males which consume feces of lactating females is more attractive to pups than excreta of males that consume feces of nonlactating females. These results suggest that group or colony odors may develop from rats eating feces of other colony members and that infant rats may be more attracted to adults that have an odor which is similar to the maternal odor than adults which have different odors.

Five to 20 mg of saponins obtained from alfalfa tops or roots were introduced intragastrically in rats also receiving oral and intravenous ring-labeled cholesterol. The saponins were tested before and after partial acid hydrolysis. Absorption of cholesterol was determined by estimation of fecal sterols and by a dual isotope technique involving assay of plasma radioactivity. Alfalfa top saponins (nonhydrolyzed) reduced absorption of cholesterol. Acid hydrolysis of alfalfa top or root saponins enhanced their ability to inhibit cholesterol absorption.

A sleep-inducing substance Factor S (FS) has been identified as a member of the muramyl peptide family of molecules which constitute the cell wall of bacteria. FS-like substances are unable to be synthesized by mammals suggesting that the symbiotic bacteria of the gastrointestinal tract are a prime source of FS. The present paper considers the relationship between the ontogenesis of Slow Wave Sleep (SWS) and the colonization of the intestine with strictly anaerobic bacteria. The practice of coprophagy in rats and rabbits is considered as an efficient method of FS ingestion during the sleep period.

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.

In previous work identification of urinary metabolites of 4'-deoxypyridoxine which had been oxidized in the 5'-position and long-term dilution of labeled urinary metabolites with unlabeled molecules suggested possible microbial contributions. In the current studies germfree guinea pigs were able to convert 4'-deoxypyridoxine to 4'-deoxy-5-pyridoxic acid demonstrating that the ability to oxidize the 5'-position is not restricted to microorganisms. Labelling curves for urinary pyridoxic acid in rats continuously fed [14C]pyridoxine since weaning were similar in conventional and germfree animals indicating that any vitamin B-6 synthesized in the intestinal tract was not readily absorbed and metabolized. Therefore, coprophagy did not make a detectable contribution to vitamin B-6 metabolism in rats receiving a nutritionally complete diet. The difficulty in achieving comparable labeling in adult animals is probably due to very slow turnover of portions of the vitamin B-6 pool and not to microbial production of vitamin B-6. The total pool calculated from the radioactivity in the germ-free rats averaged 16.2 +/- 0.8 nmol vitamin B-6 compounds/g body wt. Only 10% of the ingested label was recovered in the feces. In addition, only about 50% of the label excreted in the urine appeared as 4-pyridoxic acid in rats. These observations suggest that it may be difficult to quantitate the total urinary and fecal excretion of ingested vitamin B-6 without using tracers.

Previous data have demonstrated that thyroid gland thyroxine secretion rate in suckling rats is high and correlated with the hormonal needs of the young. Non-hormonal iodine metabolism is more elevated in the young than in the adult. The object of the present work was to measure rates of iodine transfer in 10-day old families of rats equilibrated with 125I or not. Reciprocal iodine exchange between mother and young occurred in such a way that the dam recovered about 60 p. 100 of the iodine lost in the milk. Moreover, a large store of extrathyroidal iodine was constituted in the young, particularly in the pelt.

2 novel methods of coprophagy prevention were used in iron-deficient rats to measure their effect on haemoglobin regeneration during the feeding of ferrous sulphate or several soya proteins. Neck collars produced considerable weight loss and depression in food intake compared to aluminium anal cups which were tolerated well. Both methods of coprophagy prevention reduced iron availability from a range of soya proteins and ferrous sulphate and it is suggested that the practice of coprophagy in iron-deficient and possibly iron-replete rats may overestimate iron (and possibly other mineral) absorption (retention) studies.

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.

Chronic, five times weekly administration of lidocaine (60 mg/kg, i.p.) to rats resulted in the progressive development of abnormal eating behavior and seizures. Experimental rats became omniphagic, eating significantly more feces, straw, and gauze than controls. Following an average of 15 lidocaine injections unassociated with seizures, animals began to have major motor convulsions, which then increased in frequency and duration. A pharmacological kindling mechanism is suggested for the progressive effects of lidocaine on behavior and seizures.

The rate of passage of digesta and the digestibility of a nonpurified diet were studied in adult female rats prevented from coprophagy on alternate weeks by confinement to their normal feeding tunnels in metabolism cages. In food-restricted rats a decrease in the time for the first appearance in the feces of a digesta marker was noted when prevention of coprophagy was followed by permitting rats to feed on their feces while being maintained on a restricted food intake, as compared to control rats permitted coprophagy throughout. The prevention of coprophagy had no effect on the rate of passage of digesta along the small intestine. The prevention of coprophagy had no effect on the apparent digestibility of dry matter, organic matter, energy or protein when the rats were fed ad libitum. However, when rats had lost 20% or more of their body weight by restricted feeding, digestibility of the measured constituents of the food offered in restricted amounts increased, but this effect was abolished when coprophagy was prevented.

Rats were gavaged with 144CeCI3 and either prevented from or allowed to practice coprophagy. Whole-body retention data varied widely and, in some instances, resulted in highly erratic patterns and enhanced gastrointestinal tract absorption of gavaged 144Ce in copraphagy-allowed rats. Greater whole-body retention of 144Ce was observed in coprophagy-allowed animals kept in solid plastic shoe box-type cages than in those kept in wire-bottom cages, owing to their continued access to the radioactive feces excreted within the first days after 144Ce gavage. Potential influences of coprophagy on results of experiments involving toxic materials are discussed.

Fifty-nine male Sprague-Dawley rata were subjected to an end-to-side portacaval shunt and compared with appropriate controls. During the first ten days after the operation, the liver weights decreased from an average of 4.2 to 2.3% of the body weight and thereafter remained at this level. Testicular atrophy also occurred regularly but only after the tenth postoperative day. Three weeks after the operation, the body weight of shunted rats had decreased by an average of 20%, whereas sham operated controls gained 17%. These changes were related to food intake and coprophagy. Hyper-ammonaemia developed gradually and levelled off at about 500 (μg/100 ml. Other alterations were more variable in severity. Spontaneous motor activity decreased to 12–77% of the preoperative value and was significantly correlated with changes in body weight. The electrocorticographic pattern was characterized by an average increase in rapid waves to 205% after five to six weeks, whereas the slow waves remained unchanged. These studies have established a standard of reference for further investigations with this animal model.

The effect of coprophagy prevention and antibiotics on acetyl- choline levels of kidney, brain and small intestine in weanling rats fed choline- deficient diets was studied. It was found that 5 to 6 days of dietary choline deficiency resulted in decreased concentration of acetylcholine in kidney (64% ), brain (28% ) and small intestine (30% ). Coprophagy prevention or the inclu sion of antibiotics in the diet maintained the tissues' acetylcholine at normal or near-normal levels in the choline deficient rats. These results are similar to those which have been obtained by others in germfree rats. J. Nutr. 101: 25â€"28, 1971.

SUMMARY A description is given of an inexpensive metabolism cage, in which powdered diets can be fed without measurable loss. Coprophagy is completely eliminated in rats fitted with a new design of tail cup, and in this way total collections of faeces and urine are readily achieved. Cups of a similar design have been fitted both to young male and to adult female rats, and use over periods of several weeks has revealed no ill effects. Reproducible estimates of dietary protein quality have been obtained with collection periods as short as 48 to 96 hours, and growth rates are quite good in adequately and uniformly heated rooms. 67 The principal purpose of screen-floored metabolism cages for nutritional studies in mammals is to allow urine and faeces to be quantitatively and separately collected, and several types of cage for rodents have been marketed or described. Not only is such equipment relatively expensive, but it frequently involves the excreta coming into contact with a considerable area of cage surface during the collection and separation process. This inevitably leads to loss of excreta by oxidation and deamination through spreading out on large surfacesin contact with the atmosphere. The use of tail cups in rodents partly avoids this problem. Without cups coprophagy is only slightly reduced by caging on screen as opposed to solid floors. Barnes, Fiala, McGehee & Brown (1957) estimated that 50-65 per cent of faeces are ingested by rats on screen floors. Coprophagy not only delays the ultimate excretion of compounds of dietary origin (or their products), but may alter the quantitative utilization of a nutrient and allow some diet to be utilized in a form chemically modified by the intestinal flora. This flora in turn may be changed as a result of coprophagy (Fitzgerald, Gustafsson & McDaniel, 1964). The consequences of these effects are that the degree of dietary utilization may be altered and the time required to obtain a given degree of precision in metabolic studies may be extended in the coprophagous animal. Furthermore, the

Dogs excrete most of an i.v. dose of 14 C-indomethacin unchanged in their feces. Monkeys extensively metabolize the drug to deschlorobenzoylindomethacin and excrete it in urine, and rats, without coprophagy, excrete the major metabolite, desmethylindomethacin, equally in urine and feces. 14 C-indomethacin constitutes the major radioactive species in plasma, liver and kidney of rats and monkeys. In both species, a new lipid-soluble metabolite of indomethacin was observed. The half-life of the drug in plasma varied among the three species ranging from minutes in monkeys and dogs to hours in rats. In rats, plasma clearance of indomethacin by liver, although low, was thirty times the clearance rate by kidney, and the reabsorption of indomethacin from the intestine was extensive. Desmethylindomethacin, the major metabolite, was cleared from plasma equally by liver and kidney and was not reabsorbed from the intestine of rats. Consequently, this metabolite was distributed equally in urine and feces. Indomethacin was extensively and rapidly secreted in bile by dogs, eventually excreted as unchanged drug in their feces, and minimally metabolized to deschlorobenzoylindomethacin, which was excreted in urine. Monkeys were similar to dogs in that the liver was more than ten times as effective as the kidneys in clearing total radioactivity from plasma. However, they differed from dogs in that all drug species were maximally reabsorbed from the intestine. These differences in the plasma clearance of indomethacin and its metabolites by liver and kidney and in the entero-hepatic circulation of these drug species were sufficient to account for the species differences in the distribution and excretion of indomethacin.

pH measurements were recorded from the mucosal surfaces of the rat forestomach and glandular stomach following stimulation of acid-secretion by pentagastrin. Animals containing a normal gastric bolus showed lower forestomach acidity (pH 4.3, cf. 3.2) as did coprophagic animals that contained a fecal gastric bolus (pH 6.0, cf. 3.6). Animals without a gastric bolus showed higher forestomach acidity (pH 2.3, cf. 3.0). It is concluded that the presence of a food bolus is prerequisite to maintenance of lower forestomach acidity in rats.

The purpose of this study was to determine the prevalence of coprophagy in rats with differing iron status and its effect on the measurement of iron absorption from test meals with and without bran. Two experiments were performed using radioisotope-labelled microspheres added as a non-digestible marker for the ingested faeces and the diet and 59Fe added as a marker for the non-haem iron in the test meal. In this study, coprophagy occurred at group mean rates of between 5 and 22% and was independent of the iron status of the rats or the presence or absence of bran in the diet. The relative absorption of iron, measured as the retention of 59Fe from a single meal, was affected to the same extent in groups with the same iron status, if it was affected at all. Thus comparisons of iron absorption from diets with and without bran should not be affected by coprophagy.

When a diet containing raw soybean was fed to rats, there was an increase in the synthesis of pancreatic protein, presumably exocrine protein, as evidenced by an increased uptake of [35S]cystine. There was also an increased transsulfuration of methionine sulfur as indicated by labeled sulfur transformation from methionine to cystine. This same pattern of events was produced in rats receiving a casein-containing diet when 50 mg of crystalline trypsin inhibitor was administered by gavage. However, if coprophagy was prevented, the increased uptake of [35S]cystine and [35S]methionine transsulfuration under both dietary conditions was blocked. It was found that prevention of coprophagy was without effect upon these two processes if supplementary dietary cystine was provided or if a dietary protein source with adequate cystine, i.e., heat-treated soybean, was provided. It was concluded that by practicing coprophagy, sufficient fecal cystine was being returned to the upper intestinal tract to permit some synthesis of pancreatic exocrine protein and with this stimulation of synthesis, transulfuration could proceed. This assumes that the biosynthesis of cystine is dependent upon the availability of sufficient cystine to permit active protein synthesis. In another situation where cystine requirement is high, namely, the rapidly growing rat, a limited amount of cystine was fed by providing a 12% casein diet. Either supplementary cystine or methionine was provided and it was found that both amino acids gave optimal growth in conventional rats, but when coprophagy was prevented, optimal growth was achieved only with the cystine-supplemented diet.

An attempt was made to prevent coprophagy in iron-deficient rats using plastic anal cups. Considerable damage to the anal cups occurred as a result of gnawing over periods up to 4 days. Haemoglobin iron determinations in rats with and without cups suggested that the cups had been partially successful in preventing recycling of dietary iron, and that coprophagy may be a significant factor in interpretation of haemoglobin regeneration studies on rodents.

Rats treated orally with direct brown 95, a benzidine-based dye, widely used in dyeing of textiles, plastics, paper and other materials, showed 2 peaks of excretion of mutagenic products in urine, one between 6 h and 18 h after administration and one about 30 h later. Prevention of coprophagy by fitting neck collars resulted in the disappearance of the second peak. Oral administration of carminic acid resulted in a biphasic excretion of this dye in the feces, due to coprophagy. The excretion pattern of mutagens in urine after administration of direct brown 95 corresponds with the excretion pattern in the feces of orally administered carminic acid.

Several methods for measuring cholesterol absorption in the rat have been compared. After administration of an oral dose of labeled cholesterol ((14)C or (3)H) and an intravenous dose of colloidal labeled cholesterol ((3)H or (14)C) the ratio of the two labels in plasma or whole blood 48 hr or more after dosing compared closely to the ratio of areas under the respective specific activity-time curves. The area ratio method is independent of a time lag between the appearance of oral and intravenous label in the bloodstream. Both measures of cholesterol absorption agree fairly well with a method based on measuring the unabsorbed dietary cholesterol in a pooled fecal sample. The plasma isotope ratio method gave more reproducible results than the fecal collection method when the measurement was repeated in the same animals 5 days after the first measurement. Cholesterol absorption was overestimated by the use of Tween 20-solubilized labeled cholesterol for the intravenous dose. The plasma disappearance curves of injected labeled colloidal cholesterol and cholesterol-labeled chylomicrons infused intravenously over a 3.5-hr period in the same animal coincided within experimental error from the first day until 75 days after injection. The plasma isotope ratio method for cholesterol absorption gave the same results in rats practicing coprophagy as in those in which this practice was prevented. The addition of sulfaguanidine to the diet lowered cholesterol absorption as measured by the plasma isotope ratio to the same degree as that measured by the fecal collection method.

Coprophagy (ingestion of maternal faeces) was found in young laboratory rats between the ages of 16 and 28 days. The degree of this activity during the given period was not constant; a multiple increase on about the 25th day was followed by an abrupt drop and complete cessation coincided with the time of spontaneous weaning. Coprophagy did not appear in prematurely weaned young (at 16 days) which were given faeces and was protracted in undernourished young whose weaning time was prolonged. Young weaned rats without having ingested maternal faeces displayed relative hyperphagy for solid food. This early hyperphagy had later consequences for the feeding behaviour of adult males, which looked for food and consumed it more intensively in a new environment and also hoarded it. Defensive behaviour was not affected.

The role of sucrose in the colonization of S mutans strain 6715 in conventional Sprague-Dawley rats was studied. A diet with 56% sucrose favored the oral colonization of the test strain compared to diets with 56% glucose or fructose or to laboratory chow as determined by recoveries from extracted teeth ground in tissue grinders. S mutans strain 6715 cells became well established in all rats fed a high sucrose diet with cell inoculums ranging from 10(8) to the lowest effective dose of 10(5) CFU once orally administered; in rats on nonsucrose diets, inoculation with even the highest dose only infrequently resulted in the establishment of S mutans strain 6715. Sucrose- and glucose- grown cells appeared to behave similarly. Colonization of S mutans strain 6715 occurred in all rats fed diets with a sucrose content ranging from 56 to as low as 1%. The establishment of S mutans strain 6715 on the teeth of rats fed diets with a sucrose concentration of 0.1 or 0.01% was impaired and comparable to the diet containing 56% glucose. In rats fed a high glucose diet, uniform establishment and persistence of the test strain occurred after frequent inoculations with about 5 X 10(8) CFU. The colonization under these conditions appeared to be independent of the intestinal canal as a bacterial cell source. These data suggest the possibility that S mutans can establish itself in the human mouth in the absence of dietary sucrose. In rats fed a high glucose diet and inoculated with 10(7) CFU or less, the cells gradually disappeared from the teeth; in contrast, the test strain implanted well in rats fed the sucrose favors firmer attachment of initially weakly attached cells via in situ new glucan synthesis. S mutans strain 6715 also appeared to have some affinity for teeth in the absence of dietary sucrose that may be of ecological significance. Once firmly established in rats fed a high sucrose diet, S mutans strain 6715 maintained itself in high numbers on the teeth after a switch to a high glucose diet during a 14-week period.