Significance of coprophagy for the fatty acid profile in body tissues of rabbits fed different diets.

Four groups of eight New Zealand hybrid rabbits were fattened with ad libitum access to the following pelleted experimental diets: ryegrass meal or alfalfa meal fed either alone or with oats meal in a ratio of 1:1. After 25 weeks they were slaughtered and dissected. Fatty acid (FA) profiles of caecotrophs (re-ingested fermentation products of the caecum), perirenal adipose tissue and intramuscular fat in the Musculus quadriceps were determined. With high proportions of branched-chain FA (BFA) and trans FA, and increased proportions of saturated FA relative to the diets, the caecotroph FA profile showed a clear fingerprint of anaerobe microbial lipid metabolism including biohydrogenation. By contrast, the FA profiles of adipose and lean tissue comprised high proportions of polyunsaturated FA (PUFA), whilst BFA and trans FA occurred in much lower proportions compared to the caecotrophs. Thus, coprophagy did not substantially modify the FA composition of the tissues investigated. Use of forage-only diets, compared to the oats supplemented diets, led to extraordinary high proportions of n-3 PUFA (including 18:3 and long-chain n-3) in the fat of adipose (21.3 vs. 6.7%) and lean tissue (15.4 vs. 5.7%). The forage type diet (grass vs. alfalfa) had smaller effects on the FA profiles. Indications of diet effects on endogenous desaturation, chain elongation and differential distribution of functional FA between the two tissues investigated were found.

Demonstrating coprophagy with passage markers? The example of the plains viscacha (Lagostomus maximus).

Coprophagy, or the ingestion of a certain fraction of the faeces, is a well-known strategy of small herbivores. However, the question of whether a particular species actually uses this cryptic strategy or not is not easily answered experimentally. In this study we introduce the use of ingesta passage markers as a tool to verify coprophagy in species where individual observation might be difficult. In two captive adult plains viscachas (Lagostomus maximus), we demonstrate recurrent excretion peaks for both a fluid (cobald-EDTA) and a particle (chromium-mordanted fibre) marker, the most parsimonious explanation for which is faeces re-ingestion. In addition, a literature review of graphical presentations of passage marker excretion revealed such recurrent marker peaks in a large number of studies; however, these observations were rarely explicitly contributed to a coprophagic digestion strategy. The widespread use of semi-logarithmic plots or cumulative marker excretion curves in displaying passage studies makes recurrent marker excretion peaks less evident. We conclude that passage markers offer a comparatively easy way of assessing the incidence of coprophagy. Due to the reported absence of coprophagy in rabbits, a species well-known for using this strategy, on high-protein, low-fibre diets, it is recommended that investigations of the occurrence of coprophagy should be made with animals fed challenging, high-fibre diets.

Behaviors and nutritional importance of coprophagy in captive adult and young nutrias (Myocastor coypus).

To estimate the contribution of coprophagy to protein intake, we observed the behavior, particularly that associated with coprophagy, in adult and young captive nutrias (experiment 1), and analyzed chemical composition and amino acid composition, including diaminopimeric acid (DAP), an indication of bacterial-deprived protein, of soft feces, entire hard feces, and the black part and green part of hard feces (experiment 2). Nutrias practiced coprophagy 48 times per 24 h in adults, and 28 times in young animals, which not only had a 24-h rhythm but also had 1-h or 2-h short-term rhythms. Nutrias ingested food and drank water vigorously after sunset, following which they practiced coprophagy from midnight to morning, before lying down for much of the day. When coprophagy was prevented we sampled soft feces, produced from midnight to noon, which had high (P < 0.05) concentration of crude protein (CP), DAP on a dry matter (DM) basis and 13 amino acids on a 16 g N basis than hard feces, and had a low (P < 0.05) content of acid detergent fiber (ADF). CP was greater in the black part than the green part of hard feces (P < 0.05) although ADF was less (P < 0.05). The chemical composition of the black part of hard feces was not significantly different from that of soft feces. The dry weight of soft feces excreted in experiment 1 was 34.5 g and 9.7 g DM per 24 h in adult and young animals, respectively. Using this value, the contribution of soft feces to CP intake in adult nutrias was estimated as 16%, superior to that obtained in rabbits for a diet with similar ADF concentration. To Met and Lys intake the contribution of soft feces was 26% and 19%, respectively in adult animals. These results suggest that coprophagy is quite an effective manner for nutrias to ingest extra protein.

Problems in estimating the extent of coprophagy in the rat.

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.

Effect of preventing coprophagy in the rat on neutral detergent fiber digestibility and apparent calcium absorption.

The effect of coprophagy on apparent neutral detergent fiber (NDF) digestibility, and calcium absorption was evaluated by housing rats in four types of cages: regular, metabolic, and two anticoprophagy cages: a short linear tube cage which allowed the rat forward and backward movement of about one-half a body length and a long tube cage assembled to form a square which allowed the rat to move in one direction through the tube but not turn around. Three-day weight gains of animals in the regular or metabolism cages were greater than those of rats housed in either anticoprophagy cage. In contrast, average food intake did not differ among the four housing conditions. Wet, but not dry, fecal weights were greater in the two groups of rats in the anticoprophagy cages. Neither fecal NDF (% dry wt) nor apparent NDF digestibility was affected by housing conditions. Apparent calcium absorption was decreased by the anticoprophagy housing. The differences in body weight and apparent calcium absorption suggest that prevention of coprophagy in the rats produces significant changes in the efficiency of food and nutrient utilization. The failure to detect differences in NDF digestibility indicates that coprophagy has little impact on the study of fiber digestibility.

The effects of coprophagy in the adult rat on rate of passage of digesta and on digestibility of food fed ad libitum and in restricted amounts.

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.

Effects of the withdrawal of solid food on maternal milk intake and the development of young rats.

Young rats deprived of solid food will survive on mother's milk only for about seven weeks but their development will become arrested completely. As soon as they receive solid food their development recommences immediately at the same rate as that of control infant rats. However, young rats still continue to take maternal milk for about one more week, which is the result of the gradual extinction of the sucking reflex depending the maturity of the young rats.

The entrainment of caecotrophy-rhythm of the rabbit following 6- and 12-h phase-shifts of the Zeitgeber.

By means of automatic registration of hard faeces excretion the caecotrophy-rhythm of 10 rabbits was monitored. In the animals a negative phase angle difference existed between 'lights on' and the start of caecotrophy in LD 12:12. Five rabbits practised caecotrophy once and 5 rabbits twice/24 h. Following 6-h phase-shifts of the LD-regimen the caecotrophy-rhythm was shifted in the same direction as the Zeitgeber. The time of re-entrainment for advance shifts of caecotrophy is significantly longer than for delay shifts. The inversion of the Zeitgeber causes caecotrophy to be delay-shifted in all animals.

Use of rabbits for GI drug absorption studies.

A novel procedure to control the stomach emptying rate in rabbits is presented. Rabbits were given a special solid diet for 1 week, and then the gastric contents were washed out with saline. Then the rabbits were muzzled to prevent coprophagy during the night. Fifty grams of special soft diet given to the "stomach-emptying-controlled" rabbit transferred exponentially from the stomach into the small intestine and almost disappeared from the stomach within 5 hr. Griseofulvin, indomethacin, or nalidixic acid was administered in a hard gelatin capsule or tablet, with subsequent feeding of a special soft diet. Good correlations were observed between the plasma level-time curves of these drugs in the stomach-emptying-controlled rabbits and in human subjects.