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Genetics of rabbit breeds and populations
Coat colour and hair structure
Groups of breeds by adult size and origin
Local populations and strains
Breeding
characters
Biological
characters
Genes
and the environment
Genetic improvement: selection and crossing
Conclusions
The design of rabbit housing is governed by the behavioural characteristics of the animals and their reactions to environmental temperature and humidity.
RABBIT BEHAVIOUR
Some kinds of behaviour have already been analysed in this book and others have been mentioned briefly. They all have an influence on rabbit housing so they will be summarized at this point. Since the domestication of the rabbit is recent in terms of species evolution (200-3(U) generations at most) the behaviour of the domestic rabbit is still much like that of the wild rabbit. The reactions of wild rabbits will often provide explanations for the problems of housing domestic rabbits and suggest ways of solving them.
Wild rabbits live in sedentary fashion in a territory whose size depends on the conditions of food supply. They mark their territory, their fellows and their offspring with the aid of a gland found in hair follicles under the chin. The bucks also mark off their territory with their urine. The rabbits dig burrows in which they take shelter at the slightest alert. There they live in a 'society". Before parturition' however, the doe digs a special burrow where her young are born and where she comes once a day to nurse them.
This is why domestic rabbits should have durable living quarters, providing either a refuge from disturbances or a peaceful environment that makes a refuge unnecessary. Any new and sudden change (noise, presence, smell) will make the first rabbit in the group to notice the disquieting novelty thump his hind foot to warn his fellows of danger. To prevent panic in the rabbitry the breeder should take care that changes that might upset the animals are avoided.
When a rabbit is put in a new cage he will explore it and then mark it with his smell. The more strange odours there are in the cage the longer this task will take.
The burrow is not only a refuge in case of alert, it is also a rest area during the day, as rabbits are mostly nocturnal. Temperature and humidity are far more constant in the burrow than outside.
Wild rabbits live in colonies in which females outnumber males. Each female, with or without offspring, attacks the young of other does. Bucks act as moderators at this stage. When the young males reach puberty, however, the adult males try to eliminate them as rivals by castrating them.
The method used in rational European rabbit production to prevent such conflicts is to isolate each adult rabbit in an individual cage. Before puberty, young rabbits can be raised in groups. Attempts to rear breeding animals in groups are bound to fail because the does are so aggressive towards the young, especially when the animals' living space is cramped. Females without young can be reared in groups provided each female has at least half a square metre of space for herself.
Ovulation in the does is brought on by mating (see Chapter 3, Reproduction), so one might expect mating to be possible on a quasi-permanent basis. In fact does do have a behavioural cycle of acceptance of the male but unfortunately this varies greatly from one doe to the next. Attempts at servicing often have to be repeated, which means the animals must be moved about a great deal.
The buck is so very territorial that when he is put in a female's cage his first act is to mark this new territory with his smell, while the doe tries to eliminate the intruder. But if a doe is put in a buck's cage the immediate reaction of both animals is sexual. For a receptive doe preparation for mating takes 20-120 seconds, and the act itself less than a second. For servicing therefore it is the doe that should be moved. This is relatively easy because does are calmer and weigh less than bucks (3-6 kg). For mating to be supervised, the animals need to be visible in all parts of the cage. Access to the buck's cage should be simple so that the does can be easily introduced and removed.
With this kind of mating, people have to move the animals physically within the rabbitry and this will influence the planning of the general layout of the unit to limit the distances to be covered. The rather unsatisfactory results obtained with special cages reserved for mating should be mentioned. Many males waste a lot of time marking a mating cage that is impregnated with the smell of their predecessor, and the cage is also a possible site for the spread of diseases.
Before kindling, the doe makes a nest with various materials plus fur she pulls from her abdomen. The wild doe's nest is made at the end of the private burrow she digs for kindling. The domestic rabbit does not usually have the opportunity to do this, so a private area should be set apart for her. In farm rabbitries using straw litter the doe might be satisfied to dig into the straw to make a nest. But producers have noticed that it is preferable to provide her with a nest box approximately reproducing the natural burrow.
A box like this is useful in a farm rabbitry and essential in wire cage production. After the young are born (6-12 per litter), the doe nurses them once every 24 hours for about a month. To allow the motor coordination and heat-regulation capacity of the baby rabbits to develop, the nesting box should be maintained for at least 2 weeks. It should be big enough to accommodate the doe and her litter during nursing.
Rabbits will drink and eat at any time in the 24 hours, though they tend to feed nocturnally. Intake is rather slow, even if the animals' feed is rationed. Feed and water should therefore be available over periods of several hours, whether feed is rationed or ad lib. The feed must not be allowed to get dirty, which is inevitable if it is strewn on the ground (see Chapter 5, Pathology).
From the age of 3 weeks young rabbits begin to eat the same feed as the doe. Their small size allows them to slip easily into forage racks or dry feed hoppers, so this equipment must be designed to keep them out.
HYGIENE, HABITAT AND BREEDS
There would be no point in reiterating here all the rules of hygiene dealt with in other chapters, particularly preventive hygiene. However, the design of the rabbitry will be heavily influenced by some of these rules.
One of the major rabbit diseases in traditional small-scale production using straw litter is coccidiosis. Contamination is via oocysts eliminated with the faeces. Breeders have cut the incidence of this disease by using wire-mesh floors through which the excrement drops.
The wire-mesh flooring system, combined more recently with single, portable, interchangeable cages, has led to considerable progress in disinfecting equipment. Some diseases have been cut down or even wholly eliminated. But not all rabbit breeds can adapt to this type of flooring. Heavy or nervous breeds, in particular, are subject to sore hocks, a bacterial infection developing on the foot pads and irritated by the wire mesh (too much weight per square cm). The risk is greater when the animals are raised in environments with high temperatures (31-32°C), or very high humidity (constant relative humidity above 85 percent), or when the rabbits are frequently under stress, when they thump their hind feet on the ground to warn the other rabbits of impending danger. A mesh floor also cannot be insulated, and rabbits are more liable to respiratory ailments if air flow is not controlled.
Breeders therefore have to make a decision: either they rear New Zealand White or Californian breeds, which have been adapted to mesh flooring, and thus meet modern hygiene standards, or else they rear heavier or more excitable breeds-but then how do they control coccidiosis and other diseases?
As well as these hygiene-linked problems there are other advantages and disadvantages with both mesh floors and traditional straw litter. The mesh floor through which droppings can fall makes possible automatic cleaning or very infrequent cleaning (droppings accumulate under cages). But it also makes the rabbits very dependent on the microclimate or ventilation in the rabbitry. Straw litter, on the other hand, has to be cleaned often (at least once a week) so the producer has to have the material on hand (straw, wood shavings, etc). An advantage is that a cage with a straw litter floor can be put almost anywhere, as the cage itself partly insulates the animals from variations in the external climate.
In Europe today most new production units use solely wire-mesh cages and New Zealand White or Californian rabbits. But this implies that the genetic pool of other breeds is being overlooked. Would it not be possible to design other types of flooring, recognizing that slatted floors have never been very satisfactory'? Whatever the answer, for many developing countries the wire-mesh cage will probably be only a theoretical solution for many years to come, until the special mesh necessary is made available to producers at reasonable prices.
ENVIRONMENT
Temperature is the most important factor as it directly affects a number of elements. Rabbits have constant internal (rectal) temperature so heat production and losses must vary to maintain body temperature (Table 46). They do this by modifying their feed intake level (regulating production), as described in the chapter on nutrition. They use 3 devices to modify heat losses: general body position, breathing rate and peripheral temperature, especially ear temperature (Table 46).
TABLE 46.-EXPORTATION OF HEAT, RECTAL TEMPERATURE AND EAR TEMPERATURE IN ADULT NEW ZEALAND WHITE RABBITS, ACCORDING TO AMBIENT TEMPERATURE
| Ambient temperature | Total release of heat | Release of latent heat | Body temperature | Ear temperature |
| °C | W/kg | °C | ||
| 5 | 5.3±0.93 | 0.54±0.16 | 39.3±0.3 | 9.6± 1.0 |
| 10 | 4.5 ± 0.84 | 0.57 ± 0.15 | 39.3 ± 0.2 | 14.1 ± 0.8 |
| 15 | 3.7 ± 0.78 | 0.58 ± 0.17 | 39.1 ± 0.1 | 18.7 ± 0.6 |
| 20 | 3.s ± 0.76 | 0.79 ± 0.22 | 39.0 ± 0.3 | 23.2 ± 0.9 |
| 25 | 3.2 ± 0.32 | 1.01 ± 0.23 | 39.1 ± 0.4 | 30.2 ± 2.5 |
| 30 | 3.1 ± 0.35 | 1.26 ± 0.38 | 39.1 ± 0.3 | 37.2 ± 0.7 |
| 35 | 3.7±0.35 | 2.00±0.38 | 40.5±0.8 | 39.4±0.7 |
SOURCE: Gonzalez et al, 1971.
If ambient temperature is low (below 10°C) the animals curl up to minimize the total area losing heat and lower their ear temperature. If the temperature is high (above 25-30°C), the animals stretch out so they can lose as much heat as possible by radiation and convection, and step up their ear temperature. The ears function like a car radiator. The efficiency of the cooling system depends on the air speed around the animal. At the same time the animal pants to increase heat losses through evaporation of water (latent heat). The sweat glands are not functional in rabbits and the only controlled means of latent heat evacuation is by altering the breathing rate. Perspiration (the evacuation of water through the skin) is never great because of the fur.
These systems work between 0°C and 30°C, but when ambient temperatures reach (mainly when they exceed) 35°C, rabbits can no longer regulate their internal temperature and heat prostration sets in.
The regulation methods described above, based on observation of adult animals, are applicable to young rabbits from the age of about 1 month, when they can move about and feed themselves and the juvenile coat has grown. Heat regulation of newborn rabbits is somewhat different: they have no fur and cannot correctly adjust their food intake as the doe's milk production is independent of their needs. At birth they have rather good fat reserves which help them maintain body temperature if 2 conditions are met. The surrounding temperature must be at least 28°C (3032°C if possible), and they must have other young to huddle against to reduce heat losses.
At birth, young rabbits cannot modify their body shape by curling up. The only way they can limit heat loss through convection and radiation is to huddle together with the other young in the litter. In fact, if ambient temperature varies during the day the young rabbits will move apart when the temperature is high and huddle back together when it goes down. But a sudden temperature drop may well exhaust their thermoregulation potential before they can get back in the huddle, and they can die of cold 10 cm away from the group. The newborn rabbit is blind and the incomplete myelinization of the nervous system that governs motor control hampers coordinated movement. The producer must make sure the temperature in the nest remains constant to prevent this sort of accident.
Rabbits are sensitive to very low humidity (below 55 percent) but not to very high humidity. This may be explained by the fact that wild rabbits spend much of their lives in underground burrows with a humidity level near saturation point (100 percent).
The rabbit has more to fear from abrupt changes in humidity. Constant humidity is therefore the best solution, and this will depend on the housing design. French breeders find 60-65 percent humidity levels successful, using only auxiliary heating in winter.
While the humidity level does not seem to trouble the rabbit in moderate temperatures, this is not so with temperature extremes.
When the temperature is too high (close to the rabbit's body temperature) and humidity is also high, latent heat can no longer be exported as water vapour as little water can evaporate. The result is discomfort which can be followed by prostration. Very hot spells with near 100 percent humidity can cause serious problems. Unfortunately this often occurs in tropical climates during the rainy season.
When the temperature is too low and humidity close to saturation point, water condenses on poorly insulated walls, especially at heat bridges. Water is a good heat conductor and so the cold becomes more penetrating, causing heat losses in the animals through convection and conduction. Digestive and respiratory disorders often follow. When the surrounding air is cold, excess humidity modifies the secretion and viscosity of the mucus protecting the upper respiratory apparatus.
Air which is too dry (below 60 percent relative humidity) and too hot is even more dangerous. Not only does it upset the secretion of mucus
but the ensuing evaporation shrinks the size of the droplets carrying infectious agents, enabling them to penetrate more easily the respiratory apparatus.
The rabbitry must have a certain minimum of ventilation to evacuate the harmful gases given off by the rabbits (CO2) or the straw litter and excrement (NH3, H2S, CH4, and so on); and to renew the oxygen and get rid of excess humidity (evaporation, the animals' breath) and excess heat given off by the rabbits.
Ventilation needs can vary enormously, depending especially on climate, cage type and population density. Ventilation standards for temperate climates based on several French studies are given in Table 47. This table combines the various parameters (temperature, air flow, humidity) to determine optimum air flow per kg of rabbit liveweight. If there is an imbalance, especially between air flow and temperature, accidents like those illustrated in Figure 21 occur.
It is relatively easy and cheap to measure temperature and humidity, but exact air speed measurement requires sophisticated, expensive, hard-to-get equipment such as a hot-wire anemometer (a revolving-cup anemometer is not sensitive enough). However, the producer can estimate the rate of air flow near rabbits by using a candle flame, as shown in Figure 22.
High ammonia air levels-20-30 parts per million (ppm)-greatly weaken the rabbits' upper respiratory tract and open the door to bacteria such as pasteurella and bordetella. To keep NH3 air levels down, ventilation can be increased. The risk is then overventilation, with all the negative consequences illustrated in Figure 21.
TABLE47.-VENTILATION STANDARDS USED IN FRANCE FOR RABBITRIES ENCLOSED IN BUILDINGS
| Temperature | Humidity | Air speed | Air floss1 |
| °C | % | m/see | m3/h/kg liveweight |
| 12-15 | 60-65 | 0.10-0.15 | 1 at 1.5 |
| 16-18 | 70-75 | 0.15-0.20 | 2 at 2.5 |
| 19-22 | 75-80 | 0.20-0.30 | 3 at 3.5 |
| 22-25 | 80 | 0.30-0.40 | 3.5 at 4 |
Source: Morisse. 1981.
1 Cubic metro of air flow per hour for every kg liveweight.
FIGURE 21.-Effect of air speed (V) and temperature (T°) on health of rabbits (Morisse, 1981)
FIGURE 22.-Estimating air flow with a candle flame (Le Menec, 1982)
A more effective solution is to limit NH3 production from fermenting floor litter (droppings and urine) by removing the litter quickly or keeping it dry. The maximum permissible NH3 content in the air rabbits breathe is 5 ppm.
LIGHTING
Few studies have been made on the influence of light on rabbits, and these are almost exclusively concerned with the duration of lighting and seldom with light intensity. Furthermore practical recommendations on lighting are based more on observations in rabbitries than on experimental findings.
Exposure to light for 8 out of 24 hours favours spermatogenesis and sexual activity in bucks. Conversely, exposure for 14-16 hours a day favours female sexual activity and fertilization. In rational European production all breeding animals of both sexes get 16 hours of light. The slight drop in male sexual activity is amply compensated by good female reproduction rates (acceptance of the male and fertilization).
Performance is more constant in windowless rabbitries with artificial lighting than in rabbitries which supplement sunlight by artificial lighting. Twenty-four-hour light trials caused reproduction disturbances in rabbits. It therefore seems best to limit the duration to 16 hours.
Observations from different rabbitries indicate that breeding does need considerable luminosity, at least 30-40 lux. In fact, many breeders who light their premises for 16 hours a day but not uniformly find that the does receiving the least light have the worst reproduction performance cards. When light distribution is made uniform, reproduction performance picks up.
In European rabbitries lighting is provided by incandescent lamps or fluorescent tubes (neon daylight type). The latter provide the necessary lux at a lower energy cost than incandescent lamps, but their installation cost is much higher. For flat-deck units the power consumption is 3-5 W/m2 with light sources located no more than 3 m from the animals.
Very young rabbits do not really need light, but 15-16 hours per day do no harm. Twenty-four-hour lighting, however, can cause disturbances which are hard to explain, such as diarrhoea unrelated to changes in the rate of caecotrophy. So breeders use either sunlight (in rabbitries with windows) or artificial lighting for 1-2 hours a day to satisfy the young rabbits' needs, at a set time so as not to disturb caecotrophic behaviour. A much weaker light can be used for young rabbits.
Equipment in direct contact with the rabbits or their excrement becomes contaminated by the bacteria, viruses and fungi that surround the animals. Cages, fittings and building walls must be designed so they can be easily cleaned, disinfected or replaced in order that they do not in turn become sources of contamination.
Portable components which can be cleaned outside the rabbitry building are especially recommended. Away from the rabbits stronger cleaning agents and more effective methods can be used-powerful disinfectants, lengthy soaking, prolonged exposure to the sun's rays.
Some materials are easier than others to disinfect. Wood is very hard to clean, but it can be periodically replaced in countries where it is plentiful. Plywood can be disinfected by steeping it in disinfectant solutions. Galvanized iron is easy to clean and disinfect but unlike wood is a poor insulator. Concrete, provided it is smooth, can be cleaned and disinfected, but it is practically impossible to have portable concrete installations because of the weight. Glazed earthenware can also be used for certain accessories (troughs, or even nest boxes).
CAGING
Traditional European rabbitries use straw litter. This material can be replaced by any other dry fibrous product which is not rough to the touch (soft shavings, hay, industrial cotton waste and so on). The cages are either of concrete (lasting 15-30 years) or wood (lasting not more than 2 years). Cages for breeding animals usually have a 60-70 cm x 80-100 cm floor space at least, and are 50-60 cm high. Identical cages are often used for fattening 5-6 young rabbits (to 2.5-2.8 kg). The litter should be replaced weekly to control parasitism.
A variation called "deep litter" is used in slightly taller cages. The floor is covered with a bed (minimum thickness 15-20 cm) of absorbent material (turf, wood shavings) evenly covered with straw. Every 6-7 weeks the whole lot, absorbing layer plus accumulated straw, has to be replaced. This system saves labour in cleaning and has the advantage of the comfort provided by the straw, but it does use a great deal of absorbent material so it is only applicable where this material is both readily available and cheap.
In some regions rabbits are raised on litterless floors (hard earth or wooden planking). The hygienic conditions are nearly always deplorable (uncontrolled local humidity favouring parasitism), despite daily cleaning. This system is not recommended because of the health risks involved.
The solution to the problem of changing litter has been to separate the animal from its excrement as soon as this is dropped. The rabbits are raised above the ground on a wire-mesh or slatted floor. Wire-mesh floors should be thick enough not to injure the pads of the rabbits' feet (diameter 2.4 mm, minimum 2 mm); the mesh should be wide enough to let the droppings fall through (diameter 1-1.3 cm, according to feed) but narrow enough to prevent the feet getting caught in the mesh.
There are good commercial meshes available in Europe. These measure, for example, 25 x 13 mm, 76 x 13 mm or 19 x 19 mm. To avoid injury to the rabbits' feet the wire is welded and then galvanized. Plastic mesh is impractical because no plastic material can withstand the animals' gnawing.
Various kinds of slats have been tried: wood, bamboo, plastic and metal, but the individual slats of the structure have to be spaced about 1.3-1.5 cm apart so droppings can fall through. Problems of comfort (slippery slats) and hygiene (materials which cannot be disinfected) are unfortunately very common. Wherever possible, wire mesh is preferable to slats.
Only lightweight, calm animals or specially selected breeds (New Zealand White, Californian) can be raised entirely on wire-mesh floors. Producers often compromise by raising the male and female breeding animals on litter and the fattening stock on mesh floors. The breeding animals of heavy breeds can be reared on slatted floors and the young on wire mesh; but slatted floors must be cleaned more frequently.
The dimensions of the breeding cages using litter in France are shown in Table 48 (floor generally of wire mesh but sometimes of metal or plastic slats). As may be seen by comparing these figures with the dimensions given earlier for cages using litter, the mesh floor makes it possible to reduce the area of the breeding cages. At the same time the animal density per square metre (fattening animals) can be increased to 16 on a mesh floor compared to 10 on litter. This is because excrement is immediately eliminated, cutting the risk of parasite contamination. Densities exceeding 16 rabbits per m2 reduce growth (Table 49).
TABLE 48. CAGE SIZES FOR BREEDING ANIMALS, IN FRANCE
Front |
Depth |
Height |
|
Centimetres |
|||
| Doe's cage with inner nest box | 65-70 | 50 | 30 |
| Doe's cage with outer nest box | 50-60 | 50 | 30 |
| Buck's cage | 40 | 50 | 30 |
| Cage for future breeding animal | 30 | 50 | 30 |
Source: Fort and Martin, 1981.
TABLE 49.-INFLUENCE OF ANIMAL DENSITY-NUMBER OF RABBITS PER SQ M-ON FATTENING OF RABBITS
| Rabbits per sq m of cage | |||
| 18.7 | 15.6 | 12.5 | |
| Liveweight at 77 days (g) | 2 150a | 2 327b | 2 384b |
| Average weight gain (g/day) | 32.0a | 36.1b | 36.5b |
| Average feed intake (g/day) | 111a | 122b | 122b |
| Intake index | 3.35a | 3.39a | 3.36a |
Source: Martin, 1982.
a,b:on the same line,2 value not having the same letter differ
significantly, to the threshold P=0.05.
Cage systems vary in accessibility, supervision and comfort, as well as in convenience of waste removal. Straw-litter cages will be examined first. These are either single deckers (cages with wooden or plywood framework) or built on several levels (concrete cages, with watertight floor beneath straw litter). The principle is generally the same. Access is by a door in the front of the cage, usually made of mesh, or hardwood latticework that must be replaced rather often. The other walls have no openings. They must be built in such a way that the rabbits cannot gnaw them. A rabbit cannot chew on a flat wall but will slowly but surely gnaw away any protruding part of the cage. Some examples of proper wood construction are given in Figure 23. Obviously, softwoods can be gnawed more easily than hardwoods.
Litter removal can be made more efficient if the rear walls of the cages are designed to swing out, as shown in Figure 24. The cages in the illustrations were built for a colony of Angora rabbits (which have to be reared on litter), but can be used by any rabbitry using litter, whether the cages are of concrete, as in Figure 24, or wood.
For cages without litter, mainly cages with wire-mesh floors, the structure is usually made of metal or wood (the latter out of reach of the rabbits' teeth). Walls are usually entirely in wire mesh, but this is not obligatory. There are 4 main systems: flat-deck, Californian, inclined slope battery and compact battery. Figure 25 illustrates these 4 systems. All have been used in European rational production, which means that none is perfect. However, producers prefer the flat-deck system because it has the lowest rabbit density, thus alleviating the problems which arise when many animals are reared in the same building. The main characteristics of each system are described below.
FIGURE 24.-Swinging rear wall in concrete hutch for waste removal (Thebault et al., 1981)
Flat-deck:. In this system the cages are all on one level. They usually open at the top. They can be suspended by chains or set on feet or low walls. Floor litter drops into pits (ranging in depth from 20 cm to 1.50 m). Shallow pits are cleared daily or every 2 or 3 days and deep pits every 1 to 3 years. The advantages of the flat-deck system are:
The main drawback of the system is the low animal concentration per square metre of building, which increases the investment per animal housed despite the low-cost cages. However, flat-decks are recommended for nurseries. They could also be used for fattening animals, but at a higher investment cost per cage.
California cage. In this system the cages are staggered, one deck higher than the other but not above it. The cages on the lower level open at the top and those on the upper level at the front (poorer access). Floor litter drops beneath the cages and is collected as in the flat-deck system. Advantages of the California system are:
Drawbacks:
Inclined slope buttery. The cages are placed one above the other. Waste slides down asbestos or metal panels into troughs from which it is removed manually with scrapers, or with running water. Cages obviously open at the front. Advantages of the inclined slope are:
Drawbacks:
Compact batteries. Waste can be removed by conveyor belt or vats can be installed beneath the cages and emptied by cable-operated scrapers (manual or electric). As with the inclined slope battery, the cages must open from the front. The advantage of this system is that the maximum density of animals reduces costs per animal housed.
The drawbacks are:
WATERING
A permanent dispenser of clean water is an essential item in each cage, wherever rabbits are not fed green forage alone. Using old cans or glass or earthenware pots as drinkers can create a hygiene problem. Rabbits tend to soil their water, especially if they are reared on straw litter. The drinkers should be fastened so that the rabbits cannot overturn them and so that the breeder can easily clean and refill them once or twice a day.
One possible improvement is an inverted water-bottle drinker. A bottle is inverted over a small trough (Figure 26), which is small enough to restrict pollution. The bottle is big so that it needs to be refilled less often and the breeder can see at a glance whether the animals' water intake is normal.
The best solution is an automatic drinker in every cage (Figure 27). The open drinker guarantees that the rabbits will be watered but it is expensive and there is a high risk of water pollution. A nipple drinker requires some learning on the part of the rabbits and wastes water. Even if there is no leak, the rabbits do not drink all the water that drips out. This can then wet litter or waste. The cost, however, is usually half that of an automatic open drinker. Above all, it ensures that the rabbits will always have clean water. A nipple drinker is the only kind that can be used if the rabbits are fed meal.
FIGURE 26.-Example of inverted water-bottle drinker
Automatic drinkers are fed by water from a low-pressure tank 50-150 cm above cage level. This tank can be used to administer medicine with the water. It is usually filled either by water under pressure (automatic watering) or manually (semi-automatic watering). The tank must be in the shade so that the water will not heat, which would be bad for the rabbits.
FEED TROUGHS AND RACKS
Cages should be fitted with troughs (feed hoppers for grain or pellets, small troughs for feed mashes) or forage racks, or both, depending on how the rabbits are to be fed. Troughs must be easy to clean and disinfect, so they should be detachable.
Figure 28 shows a hopper for grain or pelleted feed. Troughs and racks should be easy to fill from outside the cage without having to open the access door, but the feed must be protected from bad weather and predators. The racks should hold at least I day's ration. the hoppers enough for 2-3 days, and the mash troughs a single ration.
The bars of the rack should be strong enough to withstand the rabbits teeth and keep out the young rabbits. They love to lie on the forage, but they soil it. The feed hopper should also have a trap to keep the young out. The width between partitions in the feed box should be about 7-8 cm for medium breeds. The bars of the racks can be more closely spaced (12 cm) to prevent waste.
FIGURE 27.-Examples of automatic drinkers
THE NEST BOX
The nest box should be considered one of the most important items of equipment in rabbit production. It directly affects the viability of the young in the pre-weaning stage, which is the high-risk mortality period (15-40 percent of liveborn rabbits). The job of the nesting box is to reproduce conditions in the burrow of a wild doe and protect the young against attacks from the outside environment so that they can get through the first few difficult days of life in optimal comfort. To do this the nest box must:
FIGURE 29.-Design for a nest box. In hot climates the top of the box can he made of wire mesh
The nest box is strongly advised for rabbitries using straw litter; it is essential in modern production. The box most recommended to meet these requirements, especially the doe's comfort when kindling and nursing, is a rectangular parallelepiped at least 50 x 25 x 25 cm. If there is a dividing panel to keep the young together, at least 30 x 30 cm must be left on that side so that the mother can nurse them in comfort (Figure 29).
The nest box should be made from materials that are impossible to gnaw, easy to disinfect, insulating, and resistant to moisture. In a well-heated rabbitry or a warm climate, galvanized iron can be used if some other material such as plywood, wood or plastic is used for the bottom. Untreated wood, fibreboard, plywood or plastic are frequently used in Europe. They insulate better than metals, but except for plastic are not always easy to disinfect.
A new type of nest box made of wire mesh with a swinging bottom is now in use in France. It works well and simplifies inspection of the litter. It is also easy to clean and disinfect. It does, however, demand a perfectly controlled environment because the young are exposed.
To comply with the habits of the doe and her young, and to make the breeder's work easier, the box should have the following features:
The doe needs materials in addition to her own fur to make a good nest. Clean straw or soft, untreated wood chips are suitable, and dried grasses can be used. Cellulose cottonwool must never be used.
The nest box can be placed inside or outside the cage. If it is outside it can he fastened to the side of the cage or preferably to the front, to make inspection easier.
