Biology of the Rabbit
by François LEBAS
Directeur de Recherches honoraire de l'INRA
English revised version of "Biologie du lapin" , translated from French by Cathy R. Martin and Joan M. Rosell
Edition 2020
                                                                                                                                  Les dernières modifications

4 - Digestive system, Digestion and Feeding behavior

         4.1 Some anatomy reminders : situation in adult
        4.2 Digestive development according to age and physiological status
         4.3 Physiology of digestion & cacotrophy
         General diagram of how digestion works in rabbits

   4.4 Feeding behaviour
          Ingestion rate
         Evolution of feed ingestion in terms of age & physiological status
         Ingestion of feed and water depending on the environment
         Feed restriction, feeding behaviour and digestive development
         Feed preferences in the rabbit


  4.1 Some anatomy reminders : situation in adult
      The alimentary canal of an adult (4-4.5 kg) or subadult (2.5-3 kg) rabbit is about 4.5 to 5 metres long. Its position in the abdominal cavity is shown in figure 10. The digestive segments and their main characteristics are described in figure 11

Figure 10 : . Position of the rabbit's viscera in the abdomen . Source: Domini (1967).

Figure 11. Diagram of the different organs in the digestive tract. Source: Lebas et al. (1996a).
      As previously indicated (chaper 3), the teeth grow continuously and their masticatory function is moderate. The salivary glands (parotid, maxillary, sublingual and zygomatic or orbital) produce saliva containing very little amylase (25 µmol of maltose obtained from the starch per mg of salivary protein, compared to 250 or 450 for the pancreatic juice). The amylase content is independent of the starch content of the feed ration or whether the animal has eaten or not (Blas et al., 1988).
      The oesophagus is between the trachea and the spinal column. It allows the alimentary bolus to move from the mouth towards the stomach only. Regurgitation never occurs, even by accident

The stomach is an elongated sac with a mucous lining. The oesophagus is connected to the stomach by the cardia. The "blind" part of the stomach is the fundus (fundus in Latin) and the opposite region is the pyloric antrum (antrum pyloricum), which ends in the pylorus. It is endowed with a powerful sphincter that regulates the transfer of food towards the small intestine.

The wall mainly secretes hydrochloric acid, pepsin and minerals (Ca, K, Mg and Na). The pH is always very acid but varies noticeably during the day, especially in the fundic region (figure 12) The highest pH (the least acid) is observed when there are caecotrophs (pH 3.5) whilst the most common pH is between 1.5 and 2.0. The secretion of pepsin and electrolyte varies in the same way and depends, in particular, on the ingestion rate of caecotrophs (Beauville and Raynaud, 1964; Salse et al., 1982). The stomach content of a 9-week-old rabbit is 90-120 g of fresh matter, depending on the time. The dry matter content varies between 16 and 21 % (Gidenne and Lebas, 1984).

The stomach wall of a very young kit (1 week old) secretes pepsin, the optimum pH àf which is between 1.8 and 2.4, as well as another peptidase, the rennin or chymosin (optimum pH is between 3.4 and 3.8). From 21 days on, the optimum pepsin pH drops to 1.2-1.8 whilst rennin is not found in a 45-day-old or 60-day-old rabbit (Angelo and Srivastava, 1979).

During lactation, endopeptidase is responsible for milk coagulation in the stomach because break of the chain of kappa-casein Pepsin secretion is important only from the age about of 30 days. In contrast, the gastric lipase secreted by a small part of the stomach wall around the cardia reaches a maximum when the kit is 30 days old. It then decreases rapidly between the ages of 30 and 60 days and until 180 days. It cannot be observed in adults. (Bernadac et al., 1991).

Figure 12. Variations of stomach pH in two regions, depending
on the time of observation.
Source: Gidenne and Lebas (1984)
  Small intestine
      The small intestine which follows the pylorus, measures about 3 m in length with a diameter of about 0.8 to 1 centimeter. It is conventionally divided into duodenum, jejunum and ileum, the terminal part. The bile duct which brings bile from the liver, opens at the beginning of the duodenum, immediately after the pylorus. Its opening into the duodenum is regulated by the sphincter of Oddi. Remember that in rabbits bile is secreted almost continuously by the liver, then stored in the gallbladder before it is evacuated in the duedenum. The pancreatic duct (also known as Santorini duct) opens towards the end of the duodenum about 40 cm from the pylorus. On the wall of small intestine, plaques of lymphoid tissue about 1 to 2 cm in diameter are observed in place. These are Peyer's patches. The multiple glands present in the wall of the small intestine secrete numerous enzymes which complement those secreted by the pancreas.
      The content of the small intestine is liquid, especially in the first part and completely empty segments of approximately 10 centimetres are quite normal. The pH, which is slightly alkaline in the first part (pH 7.2-7.5), becomes progressively more acid until it reaches 6.2 - 6.5 at the end of the ileum.
Figure 13: Nycthemeral evolution of caecal pH in young rabbits of 5 weeks and in adult subjects (18 weeks). Source: Bellier et al., 1995. (Ad libituù feeding - ingestion of caecotrophs observed from 4h to 12 h. in young rabbits, and from 8h to14h in adults)

The small intestine ends at the base of the caecum via the sacculus rotondus, which contains the ileocaecal valve.The wall of the later is formed by lymphoid tissue.The caecum forms a second reservoir ( the first is the stomach) and is 40-45 cm in length, with a mean diameter of 3 to 4 centimetres. It contains 100 - 120 g of a homogenous paste, with a mean of 22 % dry matter (DM) and a pH close to 6 (figure 13). The caecal wall is invaginated in the form of a spiral with 22-25 coils, thus increasing the mucosal surface area in contact with the caecal content. The caecal appendix (10-12 cm) is situated at the distal end of the caecum and has a clearly smaller diameter. Its wall is formed by lymphoid tissue.

Very close to the end of the small intestine or the "entrance" to the caecum, is the beginning of the colon, also known as the "exit" . The caecum thus resembles a no exit diverticulum, on the axis small intestine - colon (figure 11 above). Physiological studies show that this diverticulum-reservoir is a place of obliged transit; the contents circulate from the base to the tip, passing through the centre of the caecum and returning to the base, along the wall.

      After the cecum, is the colon of about 1.5 m. It is first characterized by the presence of haustra (small pocket-shaped bulges) over about 50 cm: this is the proximal colon. After a short section of about 1 to 1.5 cm carrying the only striated muscles of the digestive tract and called fusus coli, the wall becomes smooth in its terminal part; this part is called the distal colon. Its last part is called the rectum and ends at the anus. The latter carries the anal glands.
      The digestive tract is relatively more developed in young rabbits than in adults. It reaches its definitive size when the rabbit weighs 2.5-2.7 kg, a weight which is only 60-70 % of its adult weight. Two vital organs release their secretions into the small intestine: the liver and the pancreas. Hepatic bile contains salts and various organic substances, but no enzymes. It indirectly aids digestion. In contrast, the pancreatic juice contains a considerable amount of digestive enzymes which permit protein (trypsin, chymotrypsin), starch (amylase) and fat (lipase) degradation. In addition to their digestive functions, liver and pancreas have very important functions in relation with rabbit's general metabolism
  Conclusion on the anatomy of the digestive tract
Generally speaking, the length of the small intestine (3-3.5 m) must be underlined as well as its low relative content. The importance of the role of the stomach and caecum as reservoirs must also be underlined : 70 - 80 % of the total dry content of the digestive tract is distributed between these 2 reservoirs. Finally, the percentage of water in the digestive content may vary noticeably from one segment to another as a result of secretions from the organism, and water absorption.
  4.2 Digestive development according to age and physiological status.


Between 3 and 5 weeks of age the anterior segments of the digestive tract (stomach and small intestine) become less important, whilst the posterior ones increase significantly (figure 14). From the age of 7 weeks, the organs in the digestive tract develop less rapidly in relation to the live weight of the rabbit, in particular the colon which is always delayed by two weeks. In adult does the importance of the digestive tract decreases at the end of gestation but rapidly increases during lactation until it reaches a relative size similar to that of a 5-7-week-old rabbit, (figure 14), an evolution which demonstrates its plasticity.

Taking into account the evolution of the digestive mass and the relative proportionality existing between the weight of the organ and that of its contents, the slaughter yield systematically improves with age, at least for kits older than 6 weeks (figures 15 and 16). The weight of the raw skin, which is another important element of carcass yield, only increases slightly from 14.5% up to 15.1% of the live weight between 50 and 150 days, whereas the digestive mass decreases in the sames interval of age from 23 % of the live weight at 50 days, to less than 15 % at 150 days (Combes et al., 2000). The evolution of slaughter yield may be a little bit different from one rabbit line to the other ((Figure 16)

Figure 14. Evolution of the relative weight of the digestive tract segments in the rabbit (empty organs, weights expressed in g per kg live weight) according to age between 3 and 11 weeks, and according to the breeding status of the adult doe. Source: Lebas and Laplace (1972 and 1974).
Figure 15. Evolution of the relative weight of the full digestive tract and slaughter yield, in a commercial strain of kits slaughtered between 50 and 150 days (Source: Combes et al., 2000).
Figure 16. Evolution of slaughter yield with the age, in two experimental strains A and B. Note: mean of 30 kits was used for each age (an equal number of both sexes) - mean weight of strain A at 6, 10 and 20 weeks: 1.355, 2.600 and 5.000 g ; mean weight of strain: B at the same ages: 1.455 -, 2.550 and 4.750 g (strain B is more immature). Source: Lebas and Retailleau (1999)
  4.3 Physiology of digestion and caecotrophy
  Digestive transit
      Consumed feed particles swiftly reach the stomach where they find a very acid medium and remain there for a few hours (about 2-4) without undergoing very significant chemical changes. Marked acidification occurs, which causes various substances to solubilise and beginns protein hydrolysis as a result of the action of the pepsin. The stomach content is progressively «injected» into the small intestine in the form of small waves caused by strong stomach contractions. From the moment it enters the small intestine, the content is diluted by the bile flow, the first intestinal secretions and, finally, by the action of the pancreatic juices. Enzymes contained in these secretions enable the release of easily absorbable elements which penetrate the intestinal wall and are transported to the cells via the blood. After remaining in the small intestine for about 1.5 h, the particles that have not been degraded enter the caecum where they remain for some time (2-12 h), during which they are attacked by the bacterial enzymes in the caecum. The elements issued of the degradation by this new method of attack (mostly volatile fatty acids) are released. They then penetrate the digestive tract wall and are absorbed into the blood.

The content of the cecum in turn is evacuated to the colon. Approximately half of the content is coarse and fine feed particles that were not previously degraded. The other half is bacterial bodies that have developed in the caecum at the expense of the elements coming from the small intestine, as well as the remains of digestive secretions also from the small intestine.

  The alternative functioning of the proximal colon: basis of the duality of excretion

Tiil this point , the function of the digestive tract of the rabbit is no different from other monogastrics. However, the dual nature of the functions of the proximal colon is unique. If the content enter the colon early in the morning, it undergoes few biochemical transformations. The colic wall secretes a mucous which progressively envelopes the pellets formed by the contractions of the large intestine wall. These pellets form an elongated cluster, called soft faeces or "caecotrophs". It is a different matter if the caecal content passes into the colon at another time during the day. In this case, the colon contracts in alternating directions; some of these contractions tend to empty the contents "normally" and others send it back towards the caecum. Due to the differences in the power and speed of movement of these contractions, the content is squeezed out like a sponge. Most of the liquid fraction, which contains soluble products and the fine particles (smaller than 0.1 mm, a dimension which includes the bacteria), is brought back to the caecum, whilst the "solid" fraction containing the coarse particles (larger than 0.3 mm), forms the hard faeces which are excreted out of the rabbit (Björnhag, 1972). In fact, thanks to this dual function the colon produces two different kinds of faeces: hard faeces and caecotrophs. Their chemical composition can be seen in table 4 below

Caecotrophs and hard faeces
(drawing from nature)
Twa hard faeces and one lost caecotroph on the soil of a cage in a raising on meadow system
Hard faeces observed under the cage of a little bit perturbated rabbits, some intermadiary soft faeces can bee seen,but no true caecotroph obsrvable
Hard faeces (classical droppings) of wild rabbits, observed in a field


Table 4 : Chemical composition of the rabbit's faeces
Means and variablity for 10 experimental diets, including complete diets and forages (according to Proto, 1980)
Hard faecs
Soft faeces (caecotrophs)
- Dry matter (%)
in % of dry matter
- proteins
- crude fibre
- lipids
- minerals (ash)

Difference between caecotropy and coprophagy clic on the button



If the hard faeces are evacuated in the litter, conversely, the caecotrophs are recovered by the animal as soon as they are released from the anus. To this end, during the emission, during an overall grooming operation, (Faure et al, 1963) the rabbit turns around, sucks up the soft faeces as soon as they come out of the anus, then swallows them without chewing them. Therefore, the rabbit can, without any inconvenience, practice the recovery of caecotrophs even if it is on a wire mesh floor. This is why if a breeder observes cecotrophs under the cages of his rabbits, it means that the animals are disturbed. In case of accumulated litter under wire mesh cages, the hard droppings roll over each other when they reach the ground and thus form "spread" piles. If caecotrophs are not picked up by the animal due to a temporary or permanent stress, the mucus around them tends to "stick" the droppings to each other. In this case, the pile of droppings under the cages (directly below the hindquarters of a rabbit when it is consuming in the feeder) is then of "pointed" shape.


      When everything is functioning normally, large quantities of soft faeces can be found in the stomach, where they account for as much as three quarters of the content (Gidenne and Lebas, 1988). The caecotrophs are digested in exactly the same way as "normal" feed. Bearing in mind the eventually recycled fractions, once, twice, even 3 or 4 times, and depending on the type of feed, the digestive transit of the rabbit lasts about 15 to 30 hours (20 hours on average). The general functioning of the digestive tract is summarized in figure 17.

It is worth remembering that half of the caecotrophs content is made of bacterial bodies and the rest is constuted by partially degraded feed residues and by the remains of secretions from the digestive tract. The bacterial bodies are an important source of proteins of high biological value, together with hydro soluble vitamins. Caecotrophy practice, a priori, is of considerable nutritional value. In a healthy rabbit fed on a balanced diet, caecotrophy provides approximately 15 - 25 % of the daily protein intake and covers the total requirements of vitamins B and C . However, this type of functioning of the digestive tract and the quantities involved limit the quantitative impact on protein nutrition, on the contrary the contribution of caecotrophy to the hydro soluble vitamins supply is essential. The administration of vitamins is often advised, for example during the days following weaning, because of the possible risk of digestive disorders which stop the hydrodulublrd vitamins supply.


This peculiar way of functioning of the digestive tract requires a minimum content of ballast such as crude fibre. In fact, if the feed contains few coarse particles, or is highly digestible, or both, transit to the caecum is very fast but the caecal content stay a long time in this organ, and becomes poorer in elements that may feed the " normal " bacteria living in this part of the digestive tract. So, it seems evident that different other bacteria can proliferate in this poor medium and frequently some of them may be harmful. It is therefore necessary to provide a minimum of ballast in the feed for reduced caecal retention time and promote a rapid transit. Dietary ballast has been in the past, mistakenly associated only with crude fibre in feeds. At present, minimum amounts of ligno-cellulose (ADF) and lignin are recommended, because they better discribed the "ballast" effect of the feeds.



      Figure 18 shows the influence of the amount of fibre ingested (fixed composition), on the feed retention time in the different segments of the digestive tract. It should be remembered that the effects on retention times in the stomach and small intestine tend to compensate each other but the differences between extreme feeds do not exceed 2 hours. On the other hand, a reduced supply of fibre has more effect on the time during which the bolus is retained in the caecum: between 9h 40 min. and 21 h 30 min if the lowest fibres quantity is taken in consideration
Figure 18. Retention time (hours) in the different digestive segments (stomach, small intestine and caecum + colon), after the ingestion of controlled amounts of fibre (NDF): between 26 and 44 g/day. Source: Gidenne (1994).

Caecotrophy regulation depends on the integrity of the digestive microbiota as well as the ingestion rate. The ingestion of caecotrophs starts 8 - 12 hours after feeding in restricted animals or after the ingestion peak in animals fed ad libitum. The ingestion rate in animals fed ad libitum and consequently the caecotrophy rate, are the result of the light period to which they are subjected (see below Feeding behaviour). It should also be pointed out that caecotrophy depends on internal regulation mechanisms which are not completely known today . For example, adrenal gland ablation implies that the animal no longer practises caecotrophy; the administration of cortisone to adrenalectomized animals enables normal caecotrophy behaviour to be resumed. It therefore appears that digestive transit in rabbits is dependent on adrenalin secretions. Stress-related hypersecretion causes hypoperistalsis (which increased retention time , effect similar to the effect of a low fibre diet) and as a consequence promote a high risk of digestive disorders .


      Caecotrophy is observed in young kits (domestic or wild) around 3 weeks old, as soon as they start consuming solids in addition to the mother's milk.

4.4 Feeding behaviour

      Feeding behaviour has been studied mostly in rabbits fed a complete pelleted diets, or in studies on feed preferences using dry or fresh feeds (grains, straws, hay, roots, amongst others). However, various studies of rabbits in semi-freedom and wild rabbits provide a better understanding of the feeding behavior of domestic rabbits raised conventionally in cages or in parks.

  Ingestion rate
      Suckling rabbits

The first feeding of a young rabbit is very usually done during parturition itself. After parturition, the doe herself decides the suckling rate for her kits and she feeds them once a day (Cross, 1952). Suckling lasts 2-3 minutes and the female does not provide direct assistance to the young, she is content to position herself correctly above the litter to give good access to all the teats. Some does occasionally feed twice a day or visit the nest several times, leading "observers" to believe that lactation occurs 4-5 times a day. Multiple suckling is not interesting, as already demonstrated by Zarrow et al. (1965), when growth rate of kits fed by the mother once or twice a day were found to be identical to that of the kits fed during unrestricted visits to the nest.. These results were confirmed more recently for example by Tudela and Balmisse in 2003 who showed that if 2 feedings per day allow the young rabbits to obtain a greater volume of milk (+ 8%), but the total quantity of nutrients obtained is the same since the average weight of the young rabbits at 21 days is strictly identical in the 2 situations as had been previously demonstrated (Table 5).


       Sucklings per 24 h
  Number of observed litters (9 kits /litter)
  Milk production in 24h ( mean of days 2 to 21)
250 g/day
271 g/day
  Average weight of one kit at 21 days
394.3 g
393.9 g
Table 5 : Milk production of rabbit does authorized to feed their litter of 9 kits, once or twice per 24 h. Two consecutive litters observed per doe, milk suckling rhythm was alternated between the 2 successives litters. Source: Tudela and Balmisse (2003).
      Sometimes, if the amount of milk is insufficient, the kits try to suckle every time the mother enters the nest, but she retains the milk. This behaviour is characteristic when milk production is insufficient.

Conversely, if the rabbits are offered to suckle twice a day at 12-hour intervals, but with a different mother, one in the morning and another in the evening, they readily accept. They can then ingest more milk (+ 37% on average, but ingestion is not x 2) and benefit from it for their growth (Table 6). It is therefore effectively the mother who determines the rhythm and the quantity of milk available to the young rabbits.


  Number of rabbit does nursing the same litter
  Test 1 - number of litters (equalized at 8 at birth)
      Milk / kit/ 24 hours (weeks 1-3)
24.6 g/d.
33.6 g/d.

      Average weight of 1 kit at 21 days

300 g
466 g
  Test 2 - number of litters (equalized at 8 at birth)
       Milk / kit/ 24 hours (weeks 1-3)
25.6 g/d.
35.7 g/d.
       Average weight of 1 kit at 21 days
342 g
446 g

Table 6: Average milk consumption and weight at 21 days of young rabbits sucking either only their own mother in the morning,
or sucking their own mother in the morning and a second rabbit doe 12 hours later.
Source: Szendrö et al. (2000)


      During the third week of life, the kits begin to move in a perfectly coordinated manner. They ingest milk, a little drinking water, + a very small quantity of mother's feed if available, + some hard faeces deposed by the mother in the nest at their intention in order to provide an adult rabbit's mictobiota to her kits. During the fourth week, kits ingest more solid feed and water than milk. Changes in feeding behaviour at this period are truly extraordinary: the young rabbit under the mother passes from a single feeding per day to a multitude of solid and liquid meals more or less alternated and distributed irregularly throughout the day, rythm characteristic of the feeding behavior of the adult. It is also during of this 4th week of life that begins the practice of cecotrophy. In fact, in the stomachs of young rabbits sacrificed at 22 days, only milk and feed are found; while in young rabbits sacrificed at 28 days cecotrophs can be identified in the stomach in addition to feed and traces of milk (for details see the article of Orengo & Gidenne, 2005). The preferentially nocturnal ingestion of the solid feed is already marked.
      It is interesting to note that when it begins to consume solid feed, the suckling rabbit has a clear preference for maternal feed even over feed which is better suited to its physiological needs. This suggests a role for the mother in learning to eat feed, but this has not been formally demonstrated. However, by playing on the appropriate flavoring of the "young rabbit" feed, it is possible to encourage them to consume more of it than maternal feed (table 7).
  The 2 free choice feeds => Maternal feed Flavoured "young" feed
 Aroma test N°1 (21 to 35 days)
   Average intake / kit 40.4 g/day 7.9 g/day
   Relative intake 83% 17%
 Aroma test N°2 (21 to 30 days)
    Average intake / kit 8.1 g/day 13.1 g/day
    Relative intake 38% 62%
Table 7: Attempt to flavor the feed intended for young rabbits before weaning :
feed intake by the young rabbits in a situation of free choice
the mother not having access to any of the 2 feeds. Source: Mousset, 2003.
      Feeding behaviour of he weaned rabbit or of adult rabbit
      At the time of weaning, the young rabbits already have 30 to 40 solid or liquid meals per 24 hours (table 8). The total time spent on meals in a 24 hour cycle is, at 6 weeks, more than 3 hours. Then rapidly it drops to under 2 hours. If the rabbit is offered a non-pelleted feed (flour or mash), the time spent eating is doubled. Whatever the animals' age, feed containing over 70 % water (green roughage or roots, for example) at a temperature of 20 ºC, provides more than the required amount of water.
Age in weeks
  Live weight and growth rate
   - weight of rabbits (g)
   - ADG g/day
  Solid feed intake (pellets , 89% DM)
   - g pellets / 24 h
   - N° of meals / 24h
   - g / meal
  Drinking water
   - g (ml) water / 24h
   - N° of drinks / 24h
   - g (ml) water / drink
  Water / Feed ratio

Table 8. Evolution of the feeding behavior of male rabbits between 6 and 18 weeks,
having permanently at their disposal a complete pelleted feed and drinking water, kept in a room at 20 ± 1°C.
Source: Prud'hon et al. (1975).


      The distribution of feed and water intakes is not homogenous during the 24 hours period (figure 19). The proportion of daily feed consumed on an hourly basis during the darkness period is greater than that ingested during the light period, for both solids and liquids. It should be pointed out that consumption is higher just before the lights are switched off in the raising room. In sub adult rabbits (3 kg New Zealand White) with 12 hours of light/24 h., nocturnal consumption represents almost two thirds of that observed in the total 24 hours cycle, due to increased feeding frequency but the amount of each meal is the same, 5-6 g per meal.

Figure 19. Hourly distribution of wáter and pelleted feed consumption over a 24-hour cycle in a 12 week old rabbit.
Source: Prud'hon et al (1975).
      As the rabbits grow, their nocturnal feeding behaviour increases. Feed intake decreases during the light period and the morning,"feeding rest" period between meals becomes longer (figure 20). The feeding behaviour of wild rabbits is even more nocturnal than that of domestic ones

Figure 20. Distribution of daily feed consumption in 2 hours increments, in 6 and 16 week old rabbits.
Average consumption of 80 and 189 g of pelleted feed per day for the 2 ages. Lighting 12 hours a day from 7 a.m. to 7 p.m.
Source: Bellier et al. (1995).
  Evolution of feed ingestion in terms of age and physiological status
      The amount of feed and water ingested depends firstly on the nature of the feed given to the rabbits at a given time, and especially on the digestible protein and energy content: high energy content tends to reduce consumption and high protein content tends to increase it . These amounts also depend on the type of animal, its age and breeding status or on the ambient temperature.
      Consumption of kits depends to a large extent on the animal's age, as well as other factors (figure 21). Using spontaneous consumption in adults as reference, (for example, 140-150 g DM/day, in New Zealand White rabbits weighing 4 kg), it was recorded that the daily consumption of a 4-week-old rabbit is one quarter, whilst its live weight corresponds to only 14 % of the adult's live weight. At 8 weeks the equivalent proportions are 62 and 42 % and at 16 weeks, 100 to 110 % and 87 %.
Figure 21: Evolution between 28 and 133 days of the average daily feed intake of by crossbred rabbits receiving a feed containing 16.5% protein, 34% NDF and 17.7% crude fiber in dry matter (DM) and having an average growth rate of 40 g per day between 28 and 77 days (source : Gidenne and Lebas, 1987).
the figures in blue correspond to the consumption observed at the ages concerned
Figure 22: Comparative evolution of live weight and of feed (pellets) and caecotrophs consumption between weaning and the adult stage (Source Gidenne and Lebas, 2005)
      The rabbit regulates its ingestion according to its energy needs, like other mammals. Chemostatic mechanisms are involved, through the nervous system and blood metabolites linked to energy metabolism. However, in monogastric animals glycemia plays a key role in the regulation of feed intake, while in ruminants plasma concentration in volatile fatty acids plays an important role. Given that the rabbit is an herbivorous monogastric, glycemia seems to play a preponderant role in relation to the concentration of VFA, but the respective role of these two metabolites (glucose vs VFA) on the regulation of ingestion remains today poorly understood.
      Voluntary ingestion is in fact proportional to metabolic body weight (PV0.75, and is approximately 900-1000 kJ ED / day / kg PV0.75 (ED: digestible energy). Chemostatic regulation would intervene beyond a DE concentration of 9 to 9.5 MJ / kg. Below this level, a physical type regulation prevails which would be linked to the state of fullness of the digestive tract.
      The ingestion of caecotrophs increases up to 2 months of age and then remains stable (figure 22). Expressed in fresh matter, it evolves from 10 g/ d to 55 g/ day between 1 and 2 months of age, and represents 15 to 35% of feed intake. However, it is possible that these values are underestimated given the measurement technique used in this work (temporary installation of mini shackles preventing re-ingestion of caecotrophs).
      Spontaneous feed consumption in rabbit females varies during the reproduction cycle (figure 23). Decreased consumption at the end of gestation is marked in all does and in some cases, solid feed intake can stop altogether on the eve of parturition. In contrast, water intake never stops. After parturition, feed ingestion increases rapidly and can exceed 100 g of dry matter per kg of live weight. Water intake is also significantly increased at this time: 200 to 250 g/day per kg of live weight, i.e. up to one liter /day for a 4 kg rabbit doe. When a doe is simultaneouly gestating and lactating, her feed consumption is comparable to that of a only lactating doe, and never exceeds this amount.
Figure 23. Evolution of feed intake in the rabbit doe. Pelleted dry feed, with 89 % dry matter.
Study carried out during gestation and subsequent lactation. Source: Lebas (1975).

  Ingestion of feed and water depending on the environment
      Effect of temperature
      The amount of energy a rabbit uses up, depends on environmental temperatures. Feed intake compensates for this and therefore also depends on the environmental temperature. Laboratory work carried out shows that when temperatures increases from 5ºC up to 30º, the consumption of growing rabbits is reduced from 180 g down to 120 g/day for dry feed, and water ingestion is increased from 330 up to 390 g/day in the same conditions (table 9). A more precise analysis of behaviour shows that when the temperature increases, the number of meals / 24h. (solid and liquid) decreases . For example young New Zealand females go from 37 solid meals at 10º C down to 27 meals /day at 30º C. On the other hand, if the amount of feed consumed in each meal decreases as a result of high temperatures (5.7 g/meal at 10° C and 20° C compared to 4.4 g at 30° C), the opposite occurs for water , the amount consumed each time increases with the temperature increase (from 11.4 up to 16.2 g per meal, at 10 °C and 30 °C).
 Relative Humidity
 Pelleted feed intake
 Water intake
 Water/Feed ratio
 Daily weight gain

Table 9. Feeding behavior of growing rabbits as a function of the ambient temperature.
Consumption and weight gain in g/ day
. Source: Eberhart (1980).
      If the consumption of growing rabbits is affected at 30 °C and above , that of breeding rabbits is equally affected as shown in figure 24. It should be noted that milk production is also affected by heat in the same proportion as the consumption of pelleted feed (at 30°C milk production is 70% of the value measured at 23° C).

Figure 24: Effect of ambient temperature on feed and water intakes, and on rabbit milk production.
(Source: Szendrö et al., 1998)
      A study carried out in Italy by Finzi et al. (1992), shows that if the temperature increases (tests carried out at 20 °C, 26 °C and 32 °C), the ingested feed/water ratio increases significantly, which is nothing new. However, the different ratios between ingestion and excretion also change (table 10). These authors propose using these ratios (the ones easiest to calculate locally), to verify the existence of thermal stress in rabbits. However, this suggestion should be validated before implementation.
Water / Feed
Urine / Feed
Water / Faeces
Urine / Faeces
Table 10. Incidence of environmental temperatures on different traits relative to
ingestion and excretion in adult rabbits
. Source: Finzi et al. (1992).
      Relation Water-Feed

If a rabbit has no access to drink water at all and there is only dry feed available (less than 14 % water), dry feed intake will stop completely within 24 hours. Under these conditions of water lack and depending on the environmental temperature (temperature and hygrometry), an adult rabbit can survive 4 to 8 days without its vital functions undergoing any irreversible alterations. However its weight can decrease by 20 to 30 % in less than a week. If only clean water is freely available a rabbit will survive 3 to 4 weeks without solid feed. As for what is considered as "normal", water ingestion increases 4 to 6 fold in a few days. Sodium chloride distributed in the water (0.45 %) reduces this increase in consumption; but potassium chloride does not (sodium is lost through the urine, not potassium). Rabbits are therefore very resistant to fasting and relatively resistant to lack of water but it should be pointed out that any limitation to the amount of water in relation to the rabbit's needs, means a proportional drop in the dry material ingested, and consequently, alterations in productivity.

In some cases, decreased water ingestion occurs because the animals cannot reach the drinking troughs. Suckling kits sometimes have to climb onto the mother to do this because they are so high up (over 25 cm between the floor of the cage and the waterer). As long as they ingest milk (70 to 75 % water in the milk) and the mother is tolerant, the kits will have no problems with the drinkers. But the situation can become dramatic after weaning, (no more mother to climb on) especially in the case of early weaning (before the end of the 4th week). The risk is further magnified for small breeds.

Figure 25: The dinker must be accessible for the young rabbits: 25 cm maximum from the floor of the cage and close to a wall

      Effect of other environnmental factors
      Other environmental factors have also been studied in domestic rabbits, such as the lighting schedule or housing systems. In the absence of light (24 hour darkness), the ingestion of the growing rabbit is slightly increased in comparison with rabbits subjected to a light program with a 24 hour cycle. In the absence of light, the rabbit organizes its feeding program on a regular cycle of 23.5 to 23.8 hours, with 5 to 6 hours devoted to the ingestion of caecotrophs. In continuous lighting, the feeding program of the rabbit is organized on a cycle of approximately 25 hours, and the total feed intake / 24h is reduced and the growth performance too.

According to Hungarian studies published in 2000, in the reproductive female, a modification of the lighting program, by introducing 2 periods of darkness of 4 hours, on cycles of 12h (light, darkness, 2 cycles/24h) reduces the ingestion and causes an increase in milk production, thus leading to better feed efficiency.


      As mentioned earlier, the type of cage also influences the feeding behavior of the rabbit. Ingestion is reduced if the density of rabbits in the cage rises, possibly due to greater competition between animals for access to the feeder, but also mainly due to reduced mobility of animals and therefore of their nutritional needs (table 11). This density effect is also observed for rabbits reared in individual cages (effect of cage dimension)
 Number of rabbits / cage
 Density : rabbits / m² of cage
- initial weight at 32 d. (g)
- average daily gain 32-68 d.
- consumption 32-42 d. (g)
- consumption 42-55 d. (g)
- Consumption 55-68 d. (g)

- Average consumption 32-38d.(g/d)

- Final weight (kg)
- Final density : kg liveweight / m²



Table 11. Feed consumption and growth of rabbits between 32 and 68 days of age, at a density
of 6 to 10 subjects per cage of 0.354 m²
. Source: Aubret and Duperray (1993); 8 cages per group.

 29-43d (g/d)
 43-57d (g/d)

 57-71d (g/d)

29-71d (g/d)

Table 12. Consumption of rabbits raised in groups of 4 or 30, from 29 to 71 days of age,  at the same density of 15.6 rabbits / m².
: Maertens and Van Herck (2000).

Nevertheless, rearing growing rabbits in very large collective cages (30 subjects in 1.9 m²) authorize more movement for the animals which reduce their daily ingestion compared to that of rabbits reared at a rate of 4 per cage at the same animal density (125 vs 135 g / day). Unlike the effect of the number in the same cage (table 11), the reduction in consumption with large numbers of rabbits in larges cagess at fixed density (15.6 rabbits / m²) is evident even from the start of fattening (table 12).

Finally, the number of places in front of the feeder (1 to 6 places) for a group of 10 rabbits fed ad libitum, does not have a measurable influence on the level of the pellets consumption. It is the same for rabbits rationed not too drastically (at least 70% of consumption at will).

  Feed restriction, feeding behaviour and digestive development
      It may be necessary to limit the amount of feed given to growing rabbits for several reasons. This is for example recommended in the event of epizootic rabbitenteropathy, the ERE named EEL in French (see for example the articles in French which were devoted to this topic in the magazine part of this Website in 2003 or in 2009 or the report of the round table devoted to it by the Association Scientifique Française de Cuniculture in 2007).
      Quantitative rerstriction
      When a limited quantity of food is distributed to rabbits, the daily intake is consumed all the more quickly as the restriction is more marked. For example for rabbits housed in individual cages or in pairs, an allowance representing 85% of the pellets consumed ad libitum, is completely consumed in about 16 hours. If the allowance represents only 70% of the consumption ad libitum, it is completely consumed in just under 10 hours.
      In the case of rabbits conventionally reared at a rate of 8 per cage, a pellets allocation of 85% is completely consumed in 8 hours (98% in 5 hours - figure 26) if only one rabbit can eat at a time (effect of competition) while if two rabbits can eat simultaneously, only 89% of the same allowance are eaten in 8 hours. For more details in French on the feeding behavior of quantitatively rationed rabbits, see the article Tudela and Lebas (2006) in the Magazine section of this Website.
Figure 25. Evolution of the cumulative intake during the 8 hours following a single distribution in the morning at 8h00, of rabbits fed ad libitum (control) or of rabbits receiving only 85% of the ration of control rabbits in a feeder having only one or two consumption stations for the 8 rabbits in the cage. Source: Tudela and Lebas (2006).
      Regardless of the level of restriction, rabbits do not increase their instantaneous rate of ingestion. They increase the duration of each meal, in particular the one following the distribution, and reduce the interval between each meal. The duration of these meals is however limited by the stomach capacity which represents at most only about fifteen grams of pelleted feed for a 2 kg rabbit, knowing that the stomach of a rabbit is never empty before the start of a meal. This situation allows 8 rabbits to eat in turn, even in a feeder with only one eating station. For example, even a 60% restriction does not increase the variability in weight between the rabbits in a collective cage, which means that each of the 8 rabbits was indeed restricted at the same level and that none of them consumed the "neighbor's" share.
      Restriction of access time to the feeder
      At the end of the 1980s, the Hungarian team from Kaposvar under the direction of Zs. Szendrö carried out a systematic study of the amount of feed ingested by growing rabbits as a function of the time allowed for consumption over 24 hours (a duration per 24 hour cycle varying from ½ hour to 16 hours) in comparison with ad libitum fed rabbits (figure 27). So when rabbits have 8 hours a day to consume their ration, they consume about 80% of what rabbits fed ad libitum consume. More drastic reductions in access time result in an almost linear reduction in the quantity of feed consumed, which is reduced to 20% for an access time of only ½ hour/24h.
Figure 27. Feed consumption in 24 hours as a function of the duration of access to the feeder, expressed as a percentage of the control group fed ad libitum. Source of the graph: ASFC 2007

All these results correspond to the average calculated over the entire growing period after weaning. If, on the other hand, the evolution of the effect of the restriction of the access time on the actual consumption is of interest , it was seen that there is an adaptation over time. For example, after 8 weeks of rationning the rabbits arrive, even with only 8 hours of acces, to consume as much as those fed ad libitum. This adaptation over time has been confirmed by more recent works. For example, Foubert et al. (2007) have shown that with an access time limited to 8 hours per day, the effective restriction is 64% then 73% and finally only 83% for each of the 3 consecutive weeks following a weaning at 32 days.

The Hungarian team from Kaposvar also measured the number of meals made by the rabbits according to the number of hours of access to the feeder each day. It appears that, if they have at least 9 hours to consume their solid feed, rabbits systematically realize 30 to 35 meals per day. If they have all the day to eat, they eat at an average rate of 1.3 meals per hour (figure 28). But if the access time is restricted, this number of meals can increase to almost 4 meals per hour, during "working" hours of course. On the other hand, the duration of each meal is not significantly affected by the duration of access to the feeder over 24 hours: 3.2 minutes on average, nad the interval between meals is reduced. In total over the day, 12-week-old rabbits fed ad libitum spend about 1 hour 45 minutes eating, while if they have only 9 or 10 hours to consume their solid feed, they spend only 1 hour 20 minutes approximately.

Figure 28 : Number of meals realized per unit of time in rabbits with limited access to the feeder Source : Lebas (2007)

      Restriction of access time to the waterer

Work carried a lot of years ago out at INRA in France at Montpellier (Prud´hon et al., 1975) has shown that after one week of adaptation, 6-9 week old rabbits can access the waterer for only 10 minutes each day. The 11-14 week old or adult rabbits respectively had a pelleted feed consumption reduced to 86% of that of the control group able to drink at will. Water consumption was reduced to 84% and 76% of control . In a few days following the implementation of a strong restriction of access time to drink (½h/24h), rabbits have a very strong reduction in the consumption of solid food and water (figure 29). The reduction in the time devoted to the consumption of solid food is reduced in the same proportions, suggesting a constant rate of ingestion. Rabbits gradually adapt and stabilize their feed consumption in just over 8 days depending on the age of the animals and of the actual time of access to water.

After some times of adapatation (one or two weeks) rabbits authorized to drink water only for a limited time per 24-hour cycle, increase the frequency of their solid meals immediately after the distribution of water, (4 solid meals per hour compared to 1 only for the control rabbits). The amount of pelleted feed consumed per hour follows the same profile with a peak immediately after the water distribution (figure 30). After this initial peak of consumption, rabbits then have an hourly feed consumption profile quite similar to that of rabbits with permanently available water but with lower quantities

Figure 29: Daily water and feed consumption before and after a restrition of access to drinking water of ½h per 24h.
(Source: Lebas and Delaveau, 1975).
Figure 30 : Evolution over 48 hours of the number of solid meals per hour and of the quantity of pelleted feed consumed each hour in rabbits reveiving water ad libitum (A in green) or receiving water during 10 min /day at 9h00 ( B in yellow-beige). The experimental building was lit from 8h00 to 22h00. Source: Prud'hon et al. (1975).

Under practical conditions, access to water limited to a period of 1h30 to 4h leads to a more marked reduction in water ingestion than the induced reduction in feed consumption, in particular for the shorter periods (Figures 31 and 32). This difference in behaviour results in a reduction in the water / food ratio from 1.74 in rabbits fed ad libitum to 1.54 in those receiving water only for 1 hour 30 minutes or 2 hours per 24 hours.

It should be noted that in case of water restriction, the water / food ratio is always reduced due to a reduction in water intake more marked than that of solid feed. On the other hand, a reduction in the quantity of feed daily allocated with the same magnitude, or even more important, the ingestion of water is on the contrary greatly increased and exceeds that of control animals fed ad libitum. As a result, the water / feed ratio is greatly increased (table 13).

Ad libitum
(control = 100)

1h /day

136 g/d = 100
228 g/d = 100
Table 13 : Effects of limiting the daily duration of access to drinking water or of a reduction in the quantity of pelleted feed distributed every day, on the relative consumption of water and feed. Source: Boisot et al., (2005). Averages per 24h during the 3 weeks following weaning at 31 days.
Figure 31 : Water consumption in function of access to water
Figure 32 : Feed consumption in function of access to water
Relative consumption of rabbits with a access to water only 1.5 to 4 hours per 24h or continuously, but always fed ad libitum
Data of 3 authors, Verdelhan et al. (2004), Boisot et al. (2004) and Ben Rayana et al. (2008). The results are expressed as a percentage of the control groups with a continuous access to water and to pelleted feed.
      Feed restriction and importance of the digestive tract
      As a general rule, any rationing less than 80-85% also tends to reduce the growth rate of the animals. On the other hand, the digestive tract is significantly less affected by feed restriction than the body as a whole, as shown by the data in Table 14. Moreover, if a food restriction systematically promotes an increase in digestive content, the distribution of the latter between the different segments depends largely on the restriction mode selected.
Restriction Mode
  Ad Libitum Quantitative restriction (1)
Distibution periodicity 24h / 24
5d / 7
(= 71% of the time)

Daily distribution
of 71% of control

Distribution of 71%
twice /week

Observed consumption
(% of the control group)

100% 78.9% 70.4% 71.4%
   Slaughter weight (g)
2016 1918 1901 1875
   Average Daily Gain (g / d)
38.1 a 21.3 c 25.7 b 16.6 d
   Empty digestive tract (g)
149 a 142 b 142 b 141 b
   Digestve tract content (g)
220 a 273 b 329 c 316 c
 Digestive content found in the different segments expressed as % of the total digestive content
   - Stomach
37.3 a 33.8 c 40.9 b 39.1 b
   - Small intestine
11.8 a 11.5 a 15.0 b 12.2 a
   - Caecum
40.4 a 45.2 b 35.8 c 40.8 a
   - Colon
10.6 a 9.8 a 8.4 b 7.9 b
(1) Restriction calculated according to a previous experiment with the same pelleted diet
Table 14 : Incidence of various modes of feed restriction on digestive development in rabbits slaughtered on average at 67 days.
Source: Lebas and Laplace (1982). [Commercial complete pelleted feed containing 16.5% proteins and 14.0% crude fiber].

Due to the greater relative development of the digestive mass and especially of its content, the different modes of restriction significantly affect the slaughter yield, but the effect is directly related to the speed of growth as shown by the results of the figure 33.

Figure 33. Slaughter yield (blue dots) and proportion of full viscera (green-yellow squares) in young rabbits slaughtered at 70 days, in function of the growth rate observed during the fattening period, using different types of feed restriction.
Source: Jerôme et al. (1998) . All the rabbits were fed again ad libitum one week before slaughter.
A= control group fed ad libitum continuously
          B= 80 % quantitative restriction, with daily distribution
          C1= access to the feeder limited to 16 h / 24h., at night
          C2= access to the feeder limited to 8 h / 24 h., during the lit period
          D1= access to the feeder prohibited 2 times 8 hours each week, otherwise fed ad libitum
          D2= access to the feeder prohibited for 24 h., once a week, otherwise fed ad libitum

From a practical standpoint, it should be remembered that any restriction, reducing the growth rate, will also reduce the slaughter yield .
  Feed preferences in rabbits
      Feeding behavior of wild non-captive rabbits ("grazing" rabbits)

The wild rabbit can feed on a very wide range of plants. However, it clearly prefers graminaceous (Fescue, Brachypodium, or Digitaria for example) and consumes few dicotyledons if other plants are available. Among the dicotyledons it prefers certain leguminosae (Fabaceae, Mimosaceae, Papillonaceae, ...) and asteracea (formerly Compositae). But it should be noted that if rabbit have the choice, the consumption of carrots (Daucus carotta) is very low. Contrary to popular belief, carrots (roots or leaves) are not among the plants sought after by rabbits.

The proportion of dicotyledons and even mosses can increase during some seasons when plant availability is low. In winter and early spring, grazing by rabbits of young cereals grown can completely compromise a harvest, especially in the 30 to 100 m area from the burrow. When rabbits can choose between winter cereals grown with or without mineral fertilization (phosphorus and / or nitrogen) they clearly prefer cereals without artificial fertilization.

In a situation of choice, the rabbit can be very selective in its feeding behavior. Like many herbivores, it will prefer to ingest the leaves rather than the stem of a plant, and generally young plants or "green and tender" parts rather than dry ones. For example, he will choose a part of the plant with a high nitrogen concentration. Likewise, in a trial conducted in Ireland, rabbits grazed more intensively a particular variety of spring barley compared to 4 other winter barley varieties. This is possibly related to the composition of the plant. However, the differences in the sugar content of the 5 varieties did not fully explain this varietal choice.

At the end of winter, the rabbit has a strong appetite for the buds and young stems of some woody plants. The browsing of very young trees or their shoots can thus completely compromise the regeneration of a forest, or more specifically the regeneration of certain shrubs such as juniper or the Scotch broom (Cytisus scoparius) as is observed in France in Sologne. In winter the rabbit likes to eat the bark of some cultivated trees (not just the young stems), especially apple trees and also peach or cherry trees. The bark of apricot, pear and plum trees is generally less attacked.

In the forest, rabbits clearly prefer deciduous trees, but can also attack the bark of conifers (mainly firs and some types of pines). When the trees are very young, rabbits prefer to eat the apical or lateral shoots of fir trees, rather than those of oaks.

The basic reasons for the rabbit's feed choices remain unclear, even if they are constant. It can only be said that this behavior is under hypothalamic regulation, since lesions of the hypothalamus clearly modify the rabbit's feed choices.

Many experiments have been undertaken particularly in Australia and New Zealand to study the behavior of wild rabbits, with a view to develop baits (the end goal being the extermination of imported wild rabbits in the 19th century). It was observed a lot of variation depending on the type of bait, but also depending on the season. For example, pellets made from milling by-products (middlings + bran) are well consumed throughout the year. In contrast, the acceptability of carrots or oats changes seasonally. The addition of salt (1% or 5% NaCl) or alfalfa meal (15%) in the bait pellets made with wheat by-products significantly reduces their consumption.

Rabbit damages on a young pine tree
      Feeding behavior of domestic rabbits in a free choice situation (rabbit in cage with a choice for their feed)
      Some studies have shown that the rabbit can recognize basic flavors, such as salty, sweet, bitter, sour. He shows a preference for sweet flavors, and chooses for example a feed containing additional sugar or molasses rather than a food of the same composition containing no additional sweeter.
      In captivity, the adult rabbit can sometimes express a "delicate" feeding behavior, with a momentary refusal of ingestion after a change of feed, or a systematic refusal of certain feeds. It is then observed a scratching behavior of the content of the feeder, whether the feed is in pelleted form or in flour.

Figure 34 : Test of free choice consumption of rabbits or rats, between a feed without saponin and a feed containing various levels of saponin (source of bitterness) provided by alfalfa.
: Cheeke (1974).

If a rabbit can choose between a feed with or without an appetite stimulator, it usually chooses the feed with the "apetizer". But, if each of these 2 feeds is offered alone, there is no difference in ingestion, or in growth. The same phenomenon has also been shown with the addition of a repellent in the feed such as formalin.

On the other hand, the rabbit seems to appreciate a certain degree of bitterness in its diet. When rabbits are presented with feeds containing dehydrated alfalfa with variable levels of saponin, and therefore variable bitterness, their choice is fixed on those feeds which have a relatively high degree of bitterness (up to 3 mg/ g of saponin in the diet - figure 34). All these feeds are neglected for example by rats or pigs. On the other hand, if only feeds with a variable rate of saponin (1.8 to 6.4 mg / g of feed) are proposed, feed intake and growth are independent of the saponin concentration.

When the diet contains a toxin, such as aflatoxin, the rabbit totally refuses to consume it, or he ingests it in very small quantities. When an energetic feed (low in fiber) is distributed with a free choice with a fibrous feed, the rabbit generally prefers the first. It is probably the consequence of a specific search for energy sources (rare in nature), which is the regulatory system dominating the ingestion of the rabbit. On the other hand, for the rabbit, this can lead to an increase in the frequency of digestive disorders (lack of fibre and consequently slow digestive transit) and therefore to enhanced health risk, particularly in growing young.

When a rabbit is offered different "normal" types of feeds, its choice for one or the other is often unpredictable. When offered ad libitum dehydrated alfalfa pellets and dry maize grains, the proportion is 65% alfalfa and 35% maize. In the case of alfalfa and oats the proportion is 60/40. However, if the grains of maize are relatively humid (over 14-15 %, which may cause storage problems), the proportion of grain increases to 45-50 %.
      Feeding rabbits on roughages + a complementary concentrated feed may cause problems if the roughage does not taste good. When rabbits are free to choose between concentrated energy feed and fibre (straw, for example), they are incapable of balancing the ingestion of both feeds and growth decreases. If producers find themself in this situation, they must limit the amount of concentrated feed, or the feed that the rabbits prefer. This is what happens in the case of certain green roughages of little nutritional value. As observed by Gidenne (1985), the situation is quite different if the rabbit is offered two concentrated energy feeds, such as complete pelleted feed and green bananas. The growth rate of the rabbits with free choice is similar to that of the control (only complete pellets), and the ingestion of digestible energy is identical to that observed with only pelleted feed. In any case between weaning (5 weeks) and the end of thel (12 weeks), the proportion of bananas consumed dropped from 40% down to 28% of the daily intake of dry matter.
Finally, it should be noted that growing rabbits, which receive a pelleted feed deficient in sulfur amino acids or in lysine, and which simultaneously have a free choice between pure water and for drink a solution of the deficient amino acid, the amino acid solution is clearly preferred to pure water (table 15).
They thus succeed in having a growth similar to that of the control rabbits receiving a balanced diet. It should also be noted that in this test the drinking trough receiving the pure water solution and that receiving the amino acid solution were alternated each day. While some rabbits did indeed change the "preferred" drinker depending on its content, other rabbits did not change their "favorite" drinker but drank little or a lot, depending on the nature of its content, which corresponds to two types of behavioral adaptation.
Amino-acid in water
Préference for water with the amino acid
Lysine 1.6 /Liter

Methionine 1g/L

Methionine  3g/L
Table 15 : Preference rate of growing rabbits fed a feed deficient in an amino acid and optionally as drink pure water and a solution of the deficient amino acid in the feed. Source: Lebas and Greppi (1980).