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Utilization of caecal digesta by caecotrophy (soft faeces ingestion) in the rabbit
Livestock Production Science, 8 (1981) 361--366 Elsevier Scientific Publishing Company, Amsterdam - - Printed in The Netherlands
361
UTILIZATION OF CAECAL DIGESTA BY CAECOTROPHY (SOFT FAECES INGESTION) IN THE RABBIT
H. HORNICKE Institut f'~r Zoophysiologie, UniversitZlt Hohenheim, D-7000 Stuttgart 70 (W. Germany) (Accepted May 11 1981)
ABSTRACT HSrnicke, H., 1981. Utilization of caecal digesta by caecotrophy (soft faeces ingestion) in the rabbit. Livest. Prod. Sci., 8: 361--366. As a hindgut fermenter, the rabbit obtains the vitamins and proteins synthesized in the large intestine b y caecotrophy, i.e. the production and preferential ingestion of special soft faeces. This is a higher degree of specialization than coprophagy (reingestion of normal faeces) which is practised by many rodents. Some characteristics of caecotrophy in rabbits are described.
Foregut versus hindgut fermentation Microbial fermentation in the gastrointestinal tract enables herbivores to degrade cellulose to volatile fatty acids. Moreover, vitamins and bacterial protein are synthesized. Volatile fatty acids (VFA), because of their lipid solubility, can be readily absorbed from the fermentation chamber itself and from subsequent gut-sections (Stevens, 1970; Leng, 1978). The digestible energy provided by these fermentation processes can therefore be used independently of the location of the fermentation chamber. The ability to utilize the vitamins and proteins synthesized by the bacteria, however, is different in foregut and hindgut fermenters. Foregut fermenters, such as ruminants and some other herbivores, are able to digest the bacteria in their small intestine. Vitamins and amino acids are thus absorbed rapidly. The hindgut fermenters are less favoured in this respect. The lack of proteolytic enzymes and of transport systems for vitamins and amino acids in the colon prevents effective absorption of these valuable fermentation products.
Functions of coprophagy Hindgut fermenters use different strategies to utilize the nutrients synthesized by bacteria in the caecum (H8rnicke and BjSrnhag, 1980). Many rodents practice coprophagy, i.e. they ingest part of their faeces (Barnes,
0301-6226/81/0000--0000/$02.50 © 1981 Elsevier Scientific Publishing Company
362
1962). The advantages are the digestion of faecal bacteria and the intestinal absorption of vitamins and microbial protein. There are, however, some disadvantages. The volume of reingested faeces competes with food for intake. The concentration of digestible energy and protein is usually lower in faeces than in food. Thus when sufficient protein and energy are available to the animal, coprophagy has an overall advantage only when the diet is deficient in B-vitamins. Finally, hind-gut fermentation means a wastage of nutrients even when coprophagy is practised. Only part of the faeces (30-60% in the rat; Barnes, 1962) can be ingested. The rest must be discarded, which means a loss of vitamins and protein and a low overall digestibility.
Functions of caecotrophy Rabbits and hares have a more sophisticated system of reingestion called
caecotrophy. In comparison to coprophagy it provides some additional advantages (Table I).
Nutrient economy. During certain times of the day rabbits and hares produce and ingest special faeces (caecotrophes or soft faeces} with a high content of vitamins, protein and minerals. During the other hours they excrete hard faeces, low in minerals and high in fiber content. Figure 1 shows the differences in composition between the two types of faeces. The reingestion of caecotrophes only is an advantage in terms of nutrient economy. The digestible products of caecal fermentation are almost completely reingested while the hard faeces contain the more indigestible material. The amount of caecotrophes is considerable, usually one-third of the total (soft and hard) faecal dry matter (Fig. 2). When reingested, the soft faeces provide 5--18% of the dry matter intake and up to 30% of the daily nitrogen intake. The reingested protein is characterized by a high digestibility and an elevated content of essential amino acids. Gastric fermentation. In rabbits and hares the soft faecal pellets are covered by a mucous membrane. They are taken directly from the anus, swallowed TABLE I Some putative functions of coprophagy and caecotrophy
Functions of coprophagy (1) Supply of B-vitamins and vitamin K (2) Supply of essential amino acids (3) Supply of buffer for gastric microflora
Additional functions of caecotrophy (4) Better nutrient e c o n o m y (5) Supply of bacteria for gastric fermentation
363 %
mMol/kg DM 300
+
30
200
20
100
10
Na
K
VFA
P Oz.
Crude
fiber
True protein
0
i---] HF
[]
SF
Fig. 1. Some components of soft faeces (SF) and hard faeces (HF) in rabbits. Na, K, PO 4 and VFA in mM/kg dry matter (DM), after Bonnafous (1973); crude fiber and true protein in g/kg DM, after Kandatsu et al. (1959).
Food +SF
167g-~__ ~ 37 g ~
DM intake 20z. g
",--'~ 57g HF ..~ +37g SF
37g Caecotrophes
9/~g
reingested
Fig. 2. Feed intake and amount of hard faeces (HF) and soft faeces (SF) in six collared New Zealand rabbits (after Dietzel, 1972).
without mastication and stored in the fundic region of the stomach where they act as small fermenters (Griffiths and Davies, 1963). The bacteria, protected against gastric juice by the mucous envelope and maintained at high pH by phosphate buffer, produce amylase which, together with the salivary and food amylases, degrades food starch to maltose and glucose. Both are further transformed by the bacterial metabolism mainly to VFA, lactic acid and CO2 (HSrnicke and Mackiewicz, 1975). The function of these processes remains obscure, since the formation and utilization of VFA and lactic acid are energetically more expensive than the utilization of glucose. The storage of caecotrophe pellets in the stomach thus causes a small decrease in the utilization of feed energy but this may be outbalanced by unknown advantages. Stomach fermentation also occurs in coprophagic rodents, particularly in animals whose stomach has a large area covered with squamous epithelium
364
Stomach Fermentation Rat
Rabbit
J ~flora Autochthonous ~~.~ \,\
Caecalbacteria iGam n ~~l°USme~Is~Pe
Buffer- dependent
Pe[tet- dependent
COPROPHAGY
CAECOTROPHY
Fig. 3. Characteristics of stomach fermentation in the rat and the rabbit (after suggestions made by Moir, 1968).
(GSxtner and Pfaff, 1979). Figure 3 compares the stomach fermentation in a coprophagic animal, the rat, and a caecotrophic animal, the rabbit. In the rat the reingested faeces provide the buffer, while the bacteria are autochthonous, i.e. permanently attached to the epithelium. In the rabbit the caecotrophes provide both the buffer and the active microbes. Without caecotrophy the stomach becomes rapidly devoid of bacteria (Jilge and Meyer, 1975).
Mechanisms of hard and soft faeces formation Both hard and soft faeces originate from caecal contents. During the soft faeces period, caecal contents pass through the colon with only small changes in composition. In contrast, hard faeces are the result of complex absorptive, secretory and motor processes in the colon (Clauss, 1978; Ruckebusch and HSrnicke, 1977). They involve separation of the liquid and solid phases in the proximal colon (Bj5rnhag, 1972, 1981). Larger particles of the ingesta proceed to the distal colon to form the hard faeces. Bacteria and small food particles together with the liquid phase are transported backwards into the caecum where they undergo further fermentation and provide the material for the next caecotrophy period.
Circadian timing The formation of hard and soft faeces alternates in a precise circadian rhythm. Under light--dark conditions caecotrophy usually begins shortly before or after sunrise and continues until the early afternoon. Some animals have two caecotrophy periods; the first then begins around midnight (Jilge, 1979}. In continuous light the rhythm becomes free-running with a period
365
somewhat longer than 24 h (HSrnicke and Batsch, 1977). Under ad libitum feed intake the caecotrophy period usually begins 6--8 h following the maximum of feed consumption. In this way several body functions are phaselinked with the 24 h rhythm of meal pattern and caecotrophy. When the feeding regimen of rabbits is changed from ad libitum intake to feeding for only some hours during the day, the rhythms and their phase relationships are profoundly altered. This disruption of the internal coordination of the cyclical order of body function may have implications for practical rabbit production management.
REFERENCES Barnes, R.H., 1962. Nutritional implications of coprophagy. Nutr. Rev., 10: 289--291. BjSrnhag, G., 1972. Separation and delay of contents in the rabbit colon. Swed. J. Agric. Res., 2: 125--136. BjSrnhag, G., 1981. Separation and retrograde transport in the large intestine of herbivores. Livest. Prod. Sci.~8 : 351--360. Bonnafous, R., 1973. Quelques aspets de la physiologie colique en relation avec la dualit~ de l'excretion f~cale chez le lapin. Th~se Doctorat Sciences, Toulouse. Clauss, W., 1978. Resorption und Sekretion yon Wasser und Elektrolyten im Colon des Kaninchens im Zusammenhang mit der Bildung yon Weichkot und Hartkot. Dissertation, Hohenheim. Dietzel, Felicitas, 1972. Tagesrhythmus der Nahrungsaufnahme und der Ausscheidung yon Kot und Coecotrophe bei Kaninchen in Abh~ngigkeit yon Futterangebot und Beleuchtungswechsel. Diplomarbeit, Hohenheim. Gartner, K. and Pfaff, J., 1979. The forestomach in rats and mice, a food store without bacterial protein digestion. Zbl. Vet. Med. A., 26: 530--541. Griffiths, M. and Davies, D., 1963. The role of the soft pellets in the production of lactic acid in the rabbit stomach. J. Nutr., 80: 171--180. HSrnicke, H. and Batsch, F., 1977. Coecotrophy in rabbits -- a circadian function. J. Mammal., 58: 240--242. HSrnicke, H. and BjSrnhag, G., 1980. Coprophagy and related strategies of digesta utilisation. In: Y. Ruckebusch and P. Thivend (Editors), Digestive Physiology and Metabolism in Ruminants, MTP Press, Lancaster, pp. 707--730. HSrnicke, H. and Mackiewicz, A., 1975. Bedeutung der Coecotrophe f'dr St~rkeabbau und Bildung von D-und L-Lactat im Magen des Kaninchens. In: W.T. Binnerts (Editor), Physiologie der Verdauung, Misc. Pap., Landbouwhogesch. Wageningen, 11 : 93--98. Jilge, B., 1979. Zur circadianen Coecotrophie des Kaninchens. Z. Versuchstierk., 21 : 302--312. Jilge, B. and Meyer, H., 1975. Coprophagy-dependent changes of anaerobic bacterial flora in stomach and small intestine of rabbit. Z. Versuchstierk. 1 7 : 308--314. Kandatsu, M., Yoshihara, I. and Yoshida, T., 1959. Studies and caecal composition in rabbits. Jpn. J. Zootech. Sci., 29: 366--371. Leng, E., 1978. Absorption of inorganic ions and volatile fatty acids in the rabbit caecum. Br. J. Nutr., 40: 509--519. Moix, R.J., 1968. Ruminant digestion and evolution. In: C.F. Code (Editor), Handbook of Physiology, S e c t i o n 6: The Alimentary Canal, Vol. 5, American Physiological Society, Washington, DC, pp. 2673--2694. Ruckebusch, Y. and HDrnicke, H., 1977. Motility of the rabbit's colon and cecotrophy. Physiol. Behav., 18: 871--878.
366 Stevens, C.E., 1970. F a t t y acid transport through the rumen epithelium. In: A.T. Phillipson (Editor), Physiology of Digestion and Metabolism in the Ruminant. Oriel Press, Newcastle upon Tyne, pp. 101--112.
RESUME HSrnicke, H., 1981. Utilisation des produits de la fermentation caecale par la caecotrophie (ingestion des crottes molles) chez le lapin. Livest. Prod. Sci., 8 : 3 6 1 - - 3 6 6 (en anglais). Les lapins utilisent les vitamines et les prot~ines, synth~tis~es par les microbes dans le caecum, par la caecotrophie, c'est-~l-dire par la formation et l'ingestion pr~f~rentielle de crottes molles sp~ciales. C'est un niveau de sp~cialisation plus ~lev~ que la coprophagie (ingestion de crottes normales) pratiqu~e par de nombreux rongeurs. Quelques caract~ristiques de la caecotrophie chez les lapins sont d~crites.
KURZFASSUNG HSrnicke, H., 1981. Verwertung der Blinddarmfermentationsprodukte durch Coecotrophie (Weichkotaufnahme) beim Kaninchen. Livest. Prod. Sci., 8 : 3 6 1 - - 3 6 6 (auf Englisch). Kaninchen nutzen die durch bakterielle Synthese in Blinddarm gebildeten Vitamine und Proteine dutch Coecotrophie, d.h. die Bildung und bevorzugte Reingestion eines speziellen Weichkotes. Dies stellt gegenfiber der yon vielen Nagern praktizierten Koprophagie (Reingestion normalen Kotes) einen hSheren Grad der Spezialisierung dar. Einige Charakteristika der Coecotrophie bei Kaninchen werden beschrieben.
361
UTILIZATION OF CAECAL DIGESTA BY CAECOTROPHY (SOFT FAECES INGESTION) IN THE RABBIT
H. HORNICKE Institut f'~r Zoophysiologie, UniversitZlt Hohenheim, D-7000 Stuttgart 70 (W. Germany) (Accepted May 11 1981)
ABSTRACT HSrnicke, H., 1981. Utilization of caecal digesta by caecotrophy (soft faeces ingestion) in the rabbit. Livest. Prod. Sci., 8: 361--366. As a hindgut fermenter, the rabbit obtains the vitamins and proteins synthesized in the large intestine b y caecotrophy, i.e. the production and preferential ingestion of special soft faeces. This is a higher degree of specialization than coprophagy (reingestion of normal faeces) which is practised by many rodents. Some characteristics of caecotrophy in rabbits are described.
Foregut versus hindgut fermentation Microbial fermentation in the gastrointestinal tract enables herbivores to degrade cellulose to volatile fatty acids. Moreover, vitamins and bacterial protein are synthesized. Volatile fatty acids (VFA), because of their lipid solubility, can be readily absorbed from the fermentation chamber itself and from subsequent gut-sections (Stevens, 1970; Leng, 1978). The digestible energy provided by these fermentation processes can therefore be used independently of the location of the fermentation chamber. The ability to utilize the vitamins and proteins synthesized by the bacteria, however, is different in foregut and hindgut fermenters. Foregut fermenters, such as ruminants and some other herbivores, are able to digest the bacteria in their small intestine. Vitamins and amino acids are thus absorbed rapidly. The hindgut fermenters are less favoured in this respect. The lack of proteolytic enzymes and of transport systems for vitamins and amino acids in the colon prevents effective absorption of these valuable fermentation products.
Functions of coprophagy Hindgut fermenters use different strategies to utilize the nutrients synthesized by bacteria in the caecum (H8rnicke and BjSrnhag, 1980). Many rodents practice coprophagy, i.e. they ingest part of their faeces (Barnes,
0301-6226/81/0000--0000/$02.50 © 1981 Elsevier Scientific Publishing Company
362
1962). The advantages are the digestion of faecal bacteria and the intestinal absorption of vitamins and microbial protein. There are, however, some disadvantages. The volume of reingested faeces competes with food for intake. The concentration of digestible energy and protein is usually lower in faeces than in food. Thus when sufficient protein and energy are available to the animal, coprophagy has an overall advantage only when the diet is deficient in B-vitamins. Finally, hind-gut fermentation means a wastage of nutrients even when coprophagy is practised. Only part of the faeces (30-60% in the rat; Barnes, 1962) can be ingested. The rest must be discarded, which means a loss of vitamins and protein and a low overall digestibility.
Functions of caecotrophy Rabbits and hares have a more sophisticated system of reingestion called
caecotrophy. In comparison to coprophagy it provides some additional advantages (Table I).
Nutrient economy. During certain times of the day rabbits and hares produce and ingest special faeces (caecotrophes or soft faeces} with a high content of vitamins, protein and minerals. During the other hours they excrete hard faeces, low in minerals and high in fiber content. Figure 1 shows the differences in composition between the two types of faeces. The reingestion of caecotrophes only is an advantage in terms of nutrient economy. The digestible products of caecal fermentation are almost completely reingested while the hard faeces contain the more indigestible material. The amount of caecotrophes is considerable, usually one-third of the total (soft and hard) faecal dry matter (Fig. 2). When reingested, the soft faeces provide 5--18% of the dry matter intake and up to 30% of the daily nitrogen intake. The reingested protein is characterized by a high digestibility and an elevated content of essential amino acids. Gastric fermentation. In rabbits and hares the soft faecal pellets are covered by a mucous membrane. They are taken directly from the anus, swallowed TABLE I Some putative functions of coprophagy and caecotrophy
Functions of coprophagy (1) Supply of B-vitamins and vitamin K (2) Supply of essential amino acids (3) Supply of buffer for gastric microflora
Additional functions of caecotrophy (4) Better nutrient e c o n o m y (5) Supply of bacteria for gastric fermentation
363 %
mMol/kg DM 300
+
30
200
20
100
10
Na
K
VFA
P Oz.
Crude
fiber
True protein
0
i---] HF
[]
SF
Fig. 1. Some components of soft faeces (SF) and hard faeces (HF) in rabbits. Na, K, PO 4 and VFA in mM/kg dry matter (DM), after Bonnafous (1973); crude fiber and true protein in g/kg DM, after Kandatsu et al. (1959).
Food +SF
167g-~__ ~ 37 g ~
DM intake 20z. g
",--'~ 57g HF ..~ +37g SF
37g Caecotrophes
9/~g
reingested
Fig. 2. Feed intake and amount of hard faeces (HF) and soft faeces (SF) in six collared New Zealand rabbits (after Dietzel, 1972).
without mastication and stored in the fundic region of the stomach where they act as small fermenters (Griffiths and Davies, 1963). The bacteria, protected against gastric juice by the mucous envelope and maintained at high pH by phosphate buffer, produce amylase which, together with the salivary and food amylases, degrades food starch to maltose and glucose. Both are further transformed by the bacterial metabolism mainly to VFA, lactic acid and CO2 (HSrnicke and Mackiewicz, 1975). The function of these processes remains obscure, since the formation and utilization of VFA and lactic acid are energetically more expensive than the utilization of glucose. The storage of caecotrophe pellets in the stomach thus causes a small decrease in the utilization of feed energy but this may be outbalanced by unknown advantages. Stomach fermentation also occurs in coprophagic rodents, particularly in animals whose stomach has a large area covered with squamous epithelium
364
Stomach Fermentation Rat
Rabbit
J ~flora Autochthonous ~~.~ \,\
Caecalbacteria iGam n ~~l°USme~Is~Pe
Buffer- dependent
Pe[tet- dependent
COPROPHAGY
CAECOTROPHY
Fig. 3. Characteristics of stomach fermentation in the rat and the rabbit (after suggestions made by Moir, 1968).
(GSxtner and Pfaff, 1979). Figure 3 compares the stomach fermentation in a coprophagic animal, the rat, and a caecotrophic animal, the rabbit. In the rat the reingested faeces provide the buffer, while the bacteria are autochthonous, i.e. permanently attached to the epithelium. In the rabbit the caecotrophes provide both the buffer and the active microbes. Without caecotrophy the stomach becomes rapidly devoid of bacteria (Jilge and Meyer, 1975).
Mechanisms of hard and soft faeces formation Both hard and soft faeces originate from caecal contents. During the soft faeces period, caecal contents pass through the colon with only small changes in composition. In contrast, hard faeces are the result of complex absorptive, secretory and motor processes in the colon (Clauss, 1978; Ruckebusch and HSrnicke, 1977). They involve separation of the liquid and solid phases in the proximal colon (Bj5rnhag, 1972, 1981). Larger particles of the ingesta proceed to the distal colon to form the hard faeces. Bacteria and small food particles together with the liquid phase are transported backwards into the caecum where they undergo further fermentation and provide the material for the next caecotrophy period.
Circadian timing The formation of hard and soft faeces alternates in a precise circadian rhythm. Under light--dark conditions caecotrophy usually begins shortly before or after sunrise and continues until the early afternoon. Some animals have two caecotrophy periods; the first then begins around midnight (Jilge, 1979}. In continuous light the rhythm becomes free-running with a period
365
somewhat longer than 24 h (HSrnicke and Batsch, 1977). Under ad libitum feed intake the caecotrophy period usually begins 6--8 h following the maximum of feed consumption. In this way several body functions are phaselinked with the 24 h rhythm of meal pattern and caecotrophy. When the feeding regimen of rabbits is changed from ad libitum intake to feeding for only some hours during the day, the rhythms and their phase relationships are profoundly altered. This disruption of the internal coordination of the cyclical order of body function may have implications for practical rabbit production management.
REFERENCES Barnes, R.H., 1962. Nutritional implications of coprophagy. Nutr. Rev., 10: 289--291. BjSrnhag, G., 1972. Separation and delay of contents in the rabbit colon. Swed. J. Agric. Res., 2: 125--136. BjSrnhag, G., 1981. Separation and retrograde transport in the large intestine of herbivores. Livest. Prod. Sci.~8 : 351--360. Bonnafous, R., 1973. Quelques aspets de la physiologie colique en relation avec la dualit~ de l'excretion f~cale chez le lapin. Th~se Doctorat Sciences, Toulouse. Clauss, W., 1978. Resorption und Sekretion yon Wasser und Elektrolyten im Colon des Kaninchens im Zusammenhang mit der Bildung yon Weichkot und Hartkot. Dissertation, Hohenheim. Dietzel, Felicitas, 1972. Tagesrhythmus der Nahrungsaufnahme und der Ausscheidung yon Kot und Coecotrophe bei Kaninchen in Abh~ngigkeit yon Futterangebot und Beleuchtungswechsel. Diplomarbeit, Hohenheim. Gartner, K. and Pfaff, J., 1979. The forestomach in rats and mice, a food store without bacterial protein digestion. Zbl. Vet. Med. A., 26: 530--541. Griffiths, M. and Davies, D., 1963. The role of the soft pellets in the production of lactic acid in the rabbit stomach. J. Nutr., 80: 171--180. HSrnicke, H. and Batsch, F., 1977. Coecotrophy in rabbits -- a circadian function. J. Mammal., 58: 240--242. HSrnicke, H. and BjSrnhag, G., 1980. Coprophagy and related strategies of digesta utilisation. In: Y. Ruckebusch and P. Thivend (Editors), Digestive Physiology and Metabolism in Ruminants, MTP Press, Lancaster, pp. 707--730. HSrnicke, H. and Mackiewicz, A., 1975. Bedeutung der Coecotrophe f'dr St~rkeabbau und Bildung von D-und L-Lactat im Magen des Kaninchens. In: W.T. Binnerts (Editor), Physiologie der Verdauung, Misc. Pap., Landbouwhogesch. Wageningen, 11 : 93--98. Jilge, B., 1979. Zur circadianen Coecotrophie des Kaninchens. Z. Versuchstierk., 21 : 302--312. Jilge, B. and Meyer, H., 1975. Coprophagy-dependent changes of anaerobic bacterial flora in stomach and small intestine of rabbit. Z. Versuchstierk. 1 7 : 308--314. Kandatsu, M., Yoshihara, I. and Yoshida, T., 1959. Studies and caecal composition in rabbits. Jpn. J. Zootech. Sci., 29: 366--371. Leng, E., 1978. Absorption of inorganic ions and volatile fatty acids in the rabbit caecum. Br. J. Nutr., 40: 509--519. Moix, R.J., 1968. Ruminant digestion and evolution. In: C.F. Code (Editor), Handbook of Physiology, S e c t i o n 6: The Alimentary Canal, Vol. 5, American Physiological Society, Washington, DC, pp. 2673--2694. Ruckebusch, Y. and HDrnicke, H., 1977. Motility of the rabbit's colon and cecotrophy. Physiol. Behav., 18: 871--878.
366 Stevens, C.E., 1970. F a t t y acid transport through the rumen epithelium. In: A.T. Phillipson (Editor), Physiology of Digestion and Metabolism in the Ruminant. Oriel Press, Newcastle upon Tyne, pp. 101--112.
RESUME HSrnicke, H., 1981. Utilisation des produits de la fermentation caecale par la caecotrophie (ingestion des crottes molles) chez le lapin. Livest. Prod. Sci., 8 : 3 6 1 - - 3 6 6 (en anglais). Les lapins utilisent les vitamines et les prot~ines, synth~tis~es par les microbes dans le caecum, par la caecotrophie, c'est-~l-dire par la formation et l'ingestion pr~f~rentielle de crottes molles sp~ciales. C'est un niveau de sp~cialisation plus ~lev~ que la coprophagie (ingestion de crottes normales) pratiqu~e par de nombreux rongeurs. Quelques caract~ristiques de la caecotrophie chez les lapins sont d~crites.
KURZFASSUNG HSrnicke, H., 1981. Verwertung der Blinddarmfermentationsprodukte durch Coecotrophie (Weichkotaufnahme) beim Kaninchen. Livest. Prod. Sci., 8 : 3 6 1 - - 3 6 6 (auf Englisch). Kaninchen nutzen die durch bakterielle Synthese in Blinddarm gebildeten Vitamine und Proteine dutch Coecotrophie, d.h. die Bildung und bevorzugte Reingestion eines speziellen Weichkotes. Dies stellt gegenfiber der yon vielen Nagern praktizierten Koprophagie (Reingestion normalen Kotes) einen hSheren Grad der Spezialisierung dar. Einige Charakteristika der Coecotrophie bei Kaninchen werden beschrieben.