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Various research experiments carried out in many countries, especially in France, in the last 15 years or so has resulted in reliable recommendations for the manufacture of rabbit feeds for optimum production (meat, milk) in temperate European conditions.
The experimental technique consists of manufacturing feeds in exact but varied mixes, feeding them to rabbits, and assessing production by weight gain or number and weight of young in a litter. The best feed mixes are thus established and nutrition experts have been able to draw up recommendations for four categories: resting adults (bucks, non producing does); pregnant but not lactating does; lactating does (pregnant or not); and young rabbits from weaning to slaughter agefrom 1 to about 21/2 months.
These standards have been established for the environmental conditions in Europe and are also based on the relative costs of nutrients in those countries. They are reference standards, and can be varied slightly to suit local costs. The upper and lower limits which should not be exceeded are listed at the end of this chapter.
TABLE 20.FEED INTAKE AND GROWTH OF NEW ZEALAND WHITE RABBITS AGED BETWEEN 5 AND 9 WEEKS, RECEIVING AD LIB. A CONCENTRATED FEED RICH OR POOR IN FIBRE AND WITH AND WITHOUT WHEAT STRAW PELLETS 5 MM IN DIAMETER
|Feed rich in fibre||Feed poor in fibre|
|Feed composition (%)|
|Mode of administration||Alone||+ straw||Alone||+ straw|
|Wheat straw (S)||7.4||12.2|
|Total F and S||94.7||95.7||63.4||75.5|
|Gain in liveweight (g/d)||31.7||31.0||22.4||26.6|
Source: Reyne and SalcedoMiliani, 1981.
TABLE 21. RECOMMENDED CHEMICAL COMPOSITION OF FEEDS FOR INTENSIVELY REARED RABBITS OF DIFFERENT CATEGORIES
Components of feed,
Mixed breeding does
|Methionine + cystine||%||0.60||0.60||-||-||0.60|
|Phenylalanine + tyrosine||%||1.20||1.40||-||-||1.25|
|Indigestible crude fibre||%||12||10||12||13||12|
Source: Lebas, 1979; Lang, 1981.
Lactating does need the richest, most concentrated feed. They produce a milk three times richer than cow's milk, at the rate of 100300 g per day, and have few reserves compared to the demand made on them. The next category is growing rabbits (far more research work has been done on this than any other category). Young rabbits are followed by pregnant nonlactating does. Their feed can be slightly less rich than that of young growing rabbits. The last category is bucks, which do not need a rich diet.
Table 21 details the chemical composition of theoretically ideal feeds for each rabbit category. There are 4 broad classes of standards. First, standards on proteins and protein composition (distribution of amino acids). Proteins must supply the elements to build or rebuild rabbits bodies. The indigestible share of fibre serves to provide the slight congestion essential for the proper functioning of the digestive tract. Energy is needed to regulate body temperature as well as for the general functioning of the body. Minerals and vitamins are building blocks for certain parts of the animal (skeleton, etc.), and for the enzymes which use energy to build and rebuild the body proteins continually.
Table 21 also includes a column showing the chemical composition of a mixed feed suitable for all animals in a production unit. Its composition represents a compromise between the requirements of growing rabbits and those of lactating does. The other categories can, in fact, eat a richer feed without suffering any major drawbacks. Further on in the text it will be explained under what circumstances it is desirable to use mixed or more specialized feeds. But first, the various feed requirements are explored in greater depth.
The rabbit's response to the quality of the proteins in its diet has long been a controversial issue which has now been established beyond doubt. Researchers have found that growing rabbits need feed that contains certain amounts of 10 of the 21 amino acids that make up the proteins. These are called the basic or essential amino acids. With 2 additional amino acids which can partially replace 2 of the essential amino acids, here is the full list for rabbits: arginine, histidine, leucine, isoleucine, Iysine, phenylalanine plus tyrosine, methionine plus cystine, threonine, tryptophane and valine.
Studies on the quantities needed have been virtually confined to arginine, Iysine and the sulphur amino acids (methionine and cystine). Expressed as a percentage of the ration the minimum daily requirement is 0.6 percent of Iysine and sulphur amino acids and a least 0.8 percent arginine. The toxicity thresholds of Iysine and arginine are well above the recommended intake levels. For the sulphur amino acids, however, there is a slender margin between the amount the rabbit needs and an excess dose that would diminish its performance.
For the other essential amino acids the recommended amounts have been estimated simply on the basis of regular satisfactory diets. Where these essential amino acids are supplied by protein in the diet, 1516 percent crude proteins should be enough for fattening rabbits. Rabbits will always eat more of a balanced feed containing essential amino acids than the same feed without amino acids.
The optimum dose of crude protein for the breeding doe seems to be 1718 percent for proteins with the same amino acid balance as those needed by growing rabbits. The essential amino acid requirements of does are, in fact, still unknown. An increase of protein content to 21 percent leads to higher milk production but slightly reduces the number of young rabbits weaned in a given period.
At the present stage of knowledge the entire nitrogen intake must be made up of true proteins. So far every attempt to replace true proteins with nonprotein nitrogen such as urea and ammonium salts has failed.
The energy needed for organic synthesizing is usually supplied by carbohydrates and to a lesser extent by fats. Where there is an excess of proteins these also help to supply energy after deamination.
The growing rabbit, like the breeding doe, adjusts its feed intake according to the energy concentration of the feeds offered to it where the proteins and other dietary components are balanced. For a growing New Zealand White or Californian rabbit the daily intake is around 220240 kcal of digestible energy (DE) per kg of metabolic weight (W0.75). For the lactating doe the average amount is 300 kcal DE/kg W0.75 and tops 360 kcal during maximum milk production (15th20th day of lactation). So it is hard to set a strict energy requirement, but it has been shown that intake is only correctly regulated between 2 200 and 3 200 kcal DE/kg of feed.
Because of this, concentrated energy feed must also contain all the other required nutrients in concentrated form so that a smaller volume of feed will supply the rabbit's needs.
The rabbit is known to have a specific need for the essential fatty acid, linoleic acid, but a conventional diet containing 34 percent fats generally supplies this. The only reason for including more fat in the diet would be to raise the energy concentration, as fats provide approximately twice as much energy as carbohydrates for the same weight. Depending on the kind of basic diet (basic energy level, protein content and quality) such an input of fats might or might not be nutritionally useful. In the present context more fat seems uneconomical.
In European feed rations, the poor digestibility of the fibrous parts of raw materials such as alfalfa and straw (digestibility 1030 percent) makes them secondary to starch, for example, in covering energy needs. However, the fibrous components from tender, usually young plants are much more digestible (3060 percent). They can then provide 1020 percent of energy requirements in favourable conditions.
The fibrous parts have another function: as roughage. Content is generally evaluated on the basis of crude fibre, though this analytical technique is far from perfect. To get enough roughage for growing rabbits a 1314 percent crude fibre content seems satisfactory. For lactating does a slightly lower content is acceptable (1011 percent). The more digestible the fibrous parts the higher the total input needed to supply at least 10 percent indigestible crude fibre.
Studies on the calcium and phosphorus requirements of growing rabbits have shown they need much less than lactating does. Does transfer large amounts of minerals into their milk: 78 g a day in full lactation, of which about one quarter is calcium. Any sodium, potassium or chlorine imbalance in the diet can cause nephritis and birth accidents. The risk is particularly high when plants used in the feed have been fertilized with high rates of potassium. Some authors mention improved growth performance with excess intake of copper sulphate: 200 ppm copper. As with pigs, this must be an effect of the growth factor type.
Rabbits require watersoluble (B group and C) as well as fatsoluble vitamins (A, D, E, K). Microorganisms in the digestive flora synthesize sizable quantities of watersoluble vitamins which are utilized by the rabbit through caecotrophy. This intake is sufficient to cover maintenance requirements and for average production as far as the B group vitamins and vitamin C are concerned. However, fastgrowing animals respond favourably to the addition of 12 ppm of vitamins B1 and B6, 6 ppm of vitamin B2, and 3060 ppm of nicotinic acid (vitamin PP) in the diet. The addition of vitamin C will not influence growth, even at 1 per cent of diet. Less research has been done on fatsoluble vitamins, and the recommended intakes have been established empirically.
DEVIATING FROM STANDARD RECOMMENDATIONS
Feeds formulated in accordance with the standards given in Table 21 are satisfactory for intensive production. Rabbits can also be reared on feeds only approximating these standards, but the absolute performance level will be lower, though not necessarily uneconomical. Certain indicative values are given in Table 22. Reducing the protein intake of lactating does to 13 percent of the diet will not affect prolificacy but will reduce the weight of the young at weaning.
For crude fibre, when the intake of indigestible crude fibre is less than 10 percent of the feed ration lethal diarrhoea becomes a risk. Conversely, increasing it to above 12 percent does not wholly eliminate the risk of digestive ailments and, what is more, excessive roughage can reduce the energy value of the feed. Should energy value drop below 2 200 kcal DE/kg performance will suffer, but the animal's health will not be jeopardized.
With regard to minerals, if the feed ration is deficient in calcium and phosphorus lactating does will draw on their body reserves (mainly bone); but their total reserves are limited. Does deficient in calcium and phosphorus therefore cannot be exploited intensively.
Where there are multiple deficiencies it is hard to predict the reaction of the animals. It is best to experiment and measure impact of the feeds available. The standards listed in Table 21 provide a guide for complementary feed rations that will better serve the rabbit's needs.
MANUFACTURE AND STORAGE OF FEEDS
In Europe, rabbits are fed dry raw materials which complement one another to make a balanced feed. Once the best proportions have been established, the raw materials are weighed and put in a blender. They are usually first crushed into meal for a uniform feed mixture. If the mixture were intended for feeding chickens or pigs it could be given to the animals at this stage, but the rabbit has a very low tolerance for the dust inevitably present in meal. This problem is solved by compacting the mixture in a pelleting machine.
The ideal diameter for ordinary feeds is 34 mm, 5 mm being the maximum diameter to avoid waste (Table 23). The pellets should be no longer than 810 mm. The pelleting operation heats the product through friction, which improves nutritional value by some 57 percent compared with the meal mixture.
TABLE 22.DECLINE IN GROWTH WHEN THE LEVEL OF PROTEIN OR CERTAIN ESSENTIAL AMINO ACIDS IN THE FEED DECREASES BELOW RECOMMENDED VALUES, AND MINIMUM ACCEPTABLE LEVELS
|Reduction of proportion in ration||Decrease in weight gain||Increase in feed conversion rate||Minimum acceptable levels|
|Absolute value||Absolute value|
|Proteins (1 point)||3||8.5||+0.1||+3||12|
|Methionine (0.1 point)||2||6||+0.1||+3||0.40|
|Lysine (0.1 point)||5||14||+0.1||+3||0.40|
TABLE 23.INFLUENCE OF PELLET DIAMETER ON GROWTH OF CALIFORNIAN RABBITS AGED FROM 5 TO 12 WEEKS
|Diameter of pellets (mm)|
|Feed consumption (g/d)||117a||122a||131 b|
|Weight gain (g/d)||32.4a||33.7a||32.0a|
|Feed conversion rate||3.7a||3.7a||4.1b|
TABLE 24.EFFECT OF PRESENTATION OF FEED ON GROWTH OF YOUNG RABBITS, ACCORDING TO VARIOUS AUTHORS
|Author||Presentation||Feed intake||Liveweight gain||Feed conversion|
|g DM/d||g/d||in DM|
|Machin et al.,1980||Meal||102||26.5||3.80|
Using certain recipes rabbits can actually be fed feed in meal form (Table 24). What must be avoided at all costs is a very fine meal which would disturb the normal functioning of the rabbit's upper respiratory tract. Though it is a good filter for dust, it clogs quickly. Meal must not be given as feed where rabbits drink from a trough. The water will soon get dirty and the rabbits will immediately stop drinking and eating. A valvetype automatic watering system is recommended where meal is fed.
Feeding tests on mash (60 percent meal, 40 percent water) show it is feasible provided the troughs are kept scrupulously clean (Table 24).
In Europe, depending on the size of the production unit, feed is usually delivered in 40 to 50kg bags or in bulk. Bags are stored in a shed providing shelter from high temperatures and rain, and located near the rabbits but out of their reach. They are stored in piles away from damp ground or walls. The usual solution is a false wooden floor.
The room or shed is designed to hold a 2 months, supply. Deliveries should actually be made monthly, so feed can be used within 11/2 months of manufacture. At delivery, about 2 weeks' supply should be left over from the previous month.
For bulk delivery, feed is stored in silos that are filled from the top and emptied from the bottom. They should be completely emptied and disinfected for bacteria, fungi, etc. at least once a year.
Transport costs and, especially, a desirably fast turnover of feed stocks make mixed feed (see Table 21) appropriate for rabbitries with fewer than 200 breeding does. In units with more than 200 does it is preferable to use 2 feeds: one suitable for lactating and breeding does and one based on the standards for growing rabbits in all other categories. The use of 4 feed types is only feasible in production units with at least 1 000 does.
Types of feed
BALANCED PELLETED FEEDS
The traditional European diet for rabbits used to be cereals, bran and forage (green in summer and dried in winter). In winter, breeders also fed the animals fodder beets or carrots. This style of feeding is definitely on the way out, especially in the big producer countries like France, Italy and Spain.
In modern production systems, which account for most of the output, the animals are given balanced pelleted feeds conforming to the standards already described. A single feed type is generally used for all categories, corresponding to the mixed feed listed in Table 21. In intensive reproduction rabbitries, all rabbits except bucks are fed ad lib. Under less intensive regimes, does receive the same feed ration from the weaning of one litter to the birth of the next. The ration is normally 335 g DM per kg of liveweight per day.
Growing rabbits are always fed ad lib. when raised in a group. One watering point is sufficient for 1015 animals. The watering system must be checked regularly to ensure the animals do not suffer from lack of water due to a defective apparatus. One feeding rack is enough for 10 rabbits, but at least two are needed as a safety measure in case the pellet flow should get blocked. Each feeding place along the rack should be 78 cm long.
Breeders calculate the quantities of feed for total daily consumption for all animals as follows:
Wellrun rabbitries, in France for example, calculate 4 kg of pelleted feed consumed for each kg of liveweight marketed. This calculation includes breeding rabbits. The best rabbitries use only 3.6 kg feed to produce 1 kg live rabbit. This represents a feed expenditure of 5.96.7 kg per kg of carcass. Keeping in mind the protein content of the feed and the carcasses, this means a yield of 190220 g of highgrade animal protein from 1 kg of plant protein, a return of 1922 percent.
Pilot trials in the Federal Republic of Germany have demonstrated that growing rabbits enclosed or penned in a natural meadow receiving no fertilizer can produce 240 kg of protein per hectare (1.2 tonnes of meat) annually in the form of carcasses. This gives some idea of the forage utilization potential of rabbits, though in the trials the rabbits exhibited a modest growth rate (2025 g a day compared with the 3040 g of cageor hutchraised rabbits) and a relatively high feed intake.
Climate and soils in most developing countries, however, are very different from those found in the Federal Republic of Germany. Direct rabbit grazing also poses problems of fencing and risks from predators to the point where this technique cannot be recommended. For this reason the authors have reviewed the various wild or cultivable plants used in both tropical and nontropical regions to feed rabbits reared in confinement. Cereals are intentionally left out as they are needed for human nutrition in most developing countries.
WILD AND CULTIVATED PLANTS SUITABLE FOR RABBIT FEED
The following information only concerns plants that have been positively tested in station and other trials for use as rabbit feed. They are listed under their Latin names in alphabetical order. The countries where they are used are indicated where possible.
A "high" nutrient value means the feed has a higher dry matter content than is required for rabbits. Unless otherwise indicated, nutrient content where shown is expressed as a percentage of dry matter. For detailed chemical compositions, readers should refer to the general documents in the bibliography, particularly Gohl's work on tropical forages published by FAO (1982). Digestibility of the nutrients has not usually been determined for the rabbit specifically. Lacking these data reference should be made to forage digestibility for ruminants, but absolute values cannot be transposed, especially for the fibrous fraction.
Amaranthus This forage has a 20 percent protein content. It has been tried out in Malawi to supplement a concentrate containing 39.5 percent grain maize, 26 percent maize bran, 34 percent groundnut oilcake and 0.5 percent table salt. Reproduction and growth were satisfactory: 20 rabbits per doe per year; growth of 15 g per day from 416 weeks. Amaranthus is routinely fed to rabbits at the Bunda Agricultural College in Lilongwe, Malawi. Modern hybrid varieties conventionally grown for human food can also be used for feeding rabbits.
Arachis hypogaea. Groundnut oilcake is a high protein feed (50 percent). It can be used for feed when not overpolluted by aflatoxins. The whole groundnut can also be fed, but this puts the rabbit into direct competition with people for food so this solution should only be considered under exceptional circumstances. Groundnut tops provide green forage and hay with a high protein content. This is the conventional use at the BoboDioulasso centre in Burkina Faso. The tops can also be used after the groundnuts have been harvested, but their protein content is less: it is about 15 percent before the groundnuts are removed and less than 10 percent after threshing.
The proteins in both the tops and the groundnut cake lack the sulphur amino acids.
Beta vulgaris. Fodder and fodder sugar beets supply much of the winter feed in traditional European rabbit production. Where they can be grown, beets can supply a good percentage of the energy demand. The fibrous fraction has a high digestibility (80 percent). Beet leaves are also good for rabbits. They contain 17 to 18 percent protein, but are very rich in minerals, especially potassium, which can cause digestive problems.
Brachiaria mutica. Fed to breeding does in the Philippines, pare grass has proved far more satisfactory than elephant grass (Pennisetum purpureum) or guinea grass (Panicum maximum). However, its low protein content (1013 percent) requires a nitrogen supplement (legumes, supplementary feed).
Brachiaria ruziziensis. In Burkina Faso this forage plant is part of the basic ration produced at the BoboDioulasso centre for its rabbitry. Like all grasses, however, it has a low protein content (813 percent). For proper utilization it should be supplemented by highprotein feeds. The forage could be grown together with Stylosanthes, for example, for a better balanced feed than either plant can provide alone.
Chamaecrista aeschynomene. This tropical legume is commonly used to feed Creole rabbits in Guadeloupe and Martinique.
Cocos nucifera. Young coconuts are fed to rabbits in the same area as a diet supplement and source of roughage. The coconut milk is drunk by humans, and the husks with the tender meat are given to the rabbits, which are very fond of coconuts.
Cucurbita foetidissima. Growing naturally in the semidesert area of northern Mexico, this member of the gourd family has an enormous root that is 65 percent starch. The crushed root is sundried in 23 days and as much as 30 percent can be added to balanced concentrate in place of grain sorghum for breeding and fattening rabbits. Trials at the University of Chihuahua in Mexico demonstrated no toxic effect.
The tops and especially the fruit are rich in protein (12 to 30 percent), but utilization trials have not yet been run on rabbits. Their very bitter taste, which is unattractive to other animals, is not necessarily an obstacle for rabbits. More tests on the possibilities of this interesting semidesert plant are needed.
Daucus carota. A traditional feed for European farm rabbits, carrots can be grown in many tropical countries. They are used in Zambia, in particular, to feed rabbits. Both leaves and roots have a comparable protein content of 1213 percent, but the leaveslike beet leaves are very rich in minerals.
Eichhornia crassipes. Rabbits will eat the leaves and bulbs of water hyacinth, but only 24 percent of the energy provided by the green plant is digestible. Incorporating 25 percent water hyacinth meal in a balanced feed gives good results. Amounts of 50 percent or more are less satisfactory. The arsenic content of the rabbit meat, especially the liver and kidneys, in water hyacinth trials raised grave doubts on the plant's potential for feeding rabbits where it grows in polluted water.
In rabbitries located near the Congo River in Zaire, breeders use a local water hyacinth of which the rabbits are very fond. In New Caledonia, a local hyacinth called water lily is also a traditional feed, again greatly liked by rabbits. The whole of the plantstem, bulb and roots is eaten.
Gynura cusimba. The leaves of this forage plant contain 27 percent protein. The plant is abundant in Nepal in the dry season. Rabbits like it but cattle, sheep and goats will not touch it. This difference in feed preference is a reminder that observations valid for one species do not necessarily apply to another.
Hibiscus rosasinensis. The branches of these shrubs, which are used as living fences in the Caribbean, can be fed to rabbits, as is now the practice in Haiti, for example. The young shoots contain some 15 percent protein and 16 percent crude fibre.
Indigofera arrecta. This legume grows wild in Mozambique, even during the dry season without irrigation. It is easy to grow from the seeds of the wild plant picked in season. Its high (25 percent) protein content makes it a valuable source of nitrogen for rabbits in Mozambique, especially during the dry season.
Ipomaea batatas. Sweet potatoes are a good source of energy (70 percent starch content) for human consumption and can easily be grown in a family garden. Surplus or specially grown crops could be used as an energy feed for rabbits. The tops when well developed are also a valuable feed because of their high protein content1620 percent. Sweet potato is used as a forage for rabbits in Mauritius, Guadeloupe and Martinique, mainly in backyard rabbitries.
Ipomaea tiliacea. This Convolvulacea grows wild in Guadeloupe and Martinique and is the traditional basic feed for creole rabbits. It is not planted but simply picked from the hedges where it grows wild.
Lespedeza spp. These legumes can provide a proteinrich green forage for rabbits, and could also be dried and fed as hay.
Leucaena leucocephala. This is probably the most studied legume in station rabbit trials. Its attraction is its high protein content (28 percent) and the fact that it can be grown during the dry season. Sowing and tillage are no problem in soils where this plant grows naturally (Mauritius, for example). In the absence of symbiotic bacteria, bacterial seeding can be used (Guadaloupe and Martinique).
The presence of the amino acid mimosine, which competes with tyrosine and phenylalanine, is to some authors a limiting factor for Leucaena leucocephala. They suggest that a prudent top ration of this acacia for rabbits would be 25 percent (Mozambique). But growth trials on the island of Mauritius show that Leucaena can replace 40 and even 60 percent of balanced feeds without adversely affecting animal growth or health (Figure 5). In these trials, even where the acacia was used alone, the authors noted no incidence of diarrhoea or symptoms attributable to mimosine.
Other trials in Malawi used Leucaena as a supplementary fodder for a concentrate feed (described in the paragraph on Amaranthus) with good results for both growth and reproduction. Also tested in Malawi as a maize bran supplement, Leucaena proved satisfactory for growth (60 g a week) and better than Tridax procumbens and, especially, Pen nisetum purpureum. Used as a supplementary feed for broiler chickens, growth rates of 100110 g a week were recorded.
FIGURE 5.Weight gain trends in New Zealand White rabbits aged from 6 to 14 weeks in relation to intake of balanced feed (Ramschurn, 1978)
Despite these encouraging results the problem of mimosine remains. Mimosine toxicity is cumulative and perhaps did not show up in the growth trials, though these covered the entire fattening period. Several continuous trials in Mauritius, Togo and Malawi, using Leucaena at levels of 10 and 20 percent, have not had any ill effects on growth or reproduction. As mimosine is an amino acid, drying the forage does not reduce its toxicity to animals, though no special rabbit trials have been run on this aspect.
Manihot utilissima. Ghana's rabbit development programme includes growing cassava for feed. The inclusion of from 15 to 45 percent cassava meal (87 percent starch and 2.5 to 3 percent protein) in balanced feeds, supplemented by 200 g green forage daily, has given growth and reproduction results comparable to those obtained with the balanced control feed without cassava. But cassava should not be used to feed rabbits except where the human population already has plenty of energy foods. Moreover, cassava meal requires a protein and crude fibre supplement.
However ,cassava peels contain 6 percent protein and 10 percent crude fibre, and the leaves contain 2428 percent protein, so the potential of these two cassava products for rabbit feed should be tested in comparative trials.
Marremia tuberosa. This proteinrich (24 percent) forage is used in Mozambique to feed rabbits. It grows during the dry season.
Medicago saliva. Alfalfa is unquestionably the standard rabbit forage, wherever it can be grown. It is grown under irrigation in Mexico and Mozambique. It does not grow in hot tropical areas such as the Caribbean. Breeding and growing rabbits can be fed solely on green alfalfa. The hay is harder for them to ingest. Alfalfa's rather high saponin content makes it especially palatable to rabbits.
Mimosa pigra. No negative effects were noted in tests run on this thorny plant in Thailand. It was used to replace Brachiaria mutica in rabbit feed. Its 22 percent protein content is comparable to that of Leucaena leucocephala.
Musa spp. Rabbits can be fed on banana rejects. Bananas are rich in energy and poor in protein (56 percent) and must be supplemented. Rabbit breeders use banana rejects in various African countries and in Guadeloupe and Martinique. The leaves can also be used as green forage (Zambia, Guadeloupe and Martinique). Their protein content is 1011 percent of the dry matter. Data are available on the leaves as rabbit feed, but not on the stems. They contain only 1.52 percent protein and with a 70 percent nitrogenfree extract could make a useful energy feed.
Opuntia ficus. The aerial part of prickly pear cactus can be fed to rabbits. At levels higher than 40 percent of the feed ration, however, the risk of diarrhoea arises because the fibrous portion is highly digestible.
Panicum maximum. In various comparison trials with other forages guinea grass made a poor showing mainly because of its low protein content510 percent of the dry matter according to how ripe the grass is. Despite this, guinea grass is part of the basic feed ration for rabbits in Ghana, Guadeloupe and Martinique. Its function is mainly to provide crude fibre and a small amount of energy. There is another use for guinea grass: dried' the plant is sometimes used as straw litter for the nest box, when breeding does are raised on a mesh floor.
Pennisetum purpureum. Feed trials with breeding and growing rabbits using elephant grass gave even poorer results than guinea grass, again because of low protein content (68 percent). A Malawi trial using elephant grass as a supplement for maize bran produced growth rates of only 15 g a week compared to 60 g with Leucaena leucocephala; but it can be used as a source of crude fibre for rabbits, as is done in Guadeloupe and Martinique. A mixed crop where elephant grass supports a climbing legume such as Pueraria is planned in Zaire. The combination gives a much better balanced forage.
The dried stems of Pennisetum can be used as straw litter or bedding in the nest box.
Psilotricum boivinianum. This forage grows without irrigation in the dry season in Mozambique and has a high protein content (2021 percent), making it an attractive forage feed for rabbits.
Pueraria spp. The legumes of this genus, such as P. phaseoloides and P. javanica, are recommended as rabbit feed in different countries of Africa, especially in Ghana. P. javanica is the basic feed of many farm rabbitries in Zaire. Rabbits are very fond of it. Like Stylosanthes, Pueraria remain green even in the dry season.
Saccharum officinarum. Sugarcane can be grown in countries with wet tropical climates and is a good rabbit feed, despite its low protein content (12 percent). In an early trial in Mauritius, roughly chopped sugarcane was successfully used to replace one half the balanced concentrate feed ration with no consequent drop in performance. In a complementary trial, the same authors found that, fed ad lib., rabbits chose to replace up to 40 percent of their balanced concentrate feed with chopped sugarcane. In a similar ad lib. feeding test, Leucaena leucocephala replaced up to 60 percent of the same balanced concentrate feed. In a New Caledonia trial it was shown that rabbits prefer to eat first the dry leaves, then the green leaves and then the cane itself, chopped small.
Setaria spp. These species of forage are used in Mauritius to supplement concentrated feeds for rabbits. Like all grasses, Setaria are poor in proteins.
Solanum tuberosum. Cooked potatoes can very well be used to feed rabbits, but this puts the animals into competition with people for food. Potato peelings are part of the kitchen waste in many countries and can be used in feed. However, apart from the fact that the peelings should be fed cooked not raw great care must be taken not to use the parings of potatoes which have turned green with exposure to light. Laboratory animals stopped growing when they were given 20 g of green potato peelings a day in addition to their normal feed ration.
Sorghum vulgare. Sorghum tops as well as grain are a good rabbit feed. They are used in Ghana and Mexico.
Stylosanthes spp. Legumes of this genus can be grown in all wet and dry tropical climates. In dry areas they virtually stop growing during the dry season, but remain green. Different species have been used for rabbits, including S. gracilis (Ghana, Zaire, Burkina Faso) and S. hamata (Martinique).
Taraxacum officinale. The dandelion is among the wild plants conventionally fed to rabbits in traditional European rabbit production. The use of this composite plant as rabbit feed has also been reported in Togo.
Tridax procumbens. Considered a weed on the Malawi grasslands, the advantage of Tridax is that it grows during the dry season. Its 1213 percent protein content also makes it a good rabbit feed. The plant proved satisfactory as a concentrate feed supplement in Malawi. Growth performance trials with Tridax as a maize bran supplement, however, were poorer than trials with Leucaena leucocephala, though more promising than results from Pennisetum purpureum, probably because of the differing protein content of the three plants.
Trifolium alexandrinum. This Egyptian clover (berseem), typical of the Mediterranean climate, is virtually the only rabbit feed used in the Sudan. Feeding trials in Egypt using the clover alone produced live weights of 1.23 kg at 16 weeks for crossbred Baladi x Flanders Giant rabbits, with an average weekly gain of 67 g. Like all legumes this clover variety has a high protein content.
Vicia spp. Wild vetches, grown alone or interplanted with grasses, can supply a proteinrich forage attractive to rabbits. The plant grows so quickly, however' that the tendency is to use it as hay, unless planting can be staggered for a continuing crop.
Vigna sinensis. These wild peas of Guadeloupe and Martinique supply nitrogenrich green forage and grain. Both V. sinensis and V. unguiculata are used as rabbit feed in these islands.
Zea mays. Although maize grain is needed as food for people in most developing countries, its use as fodder would be feasible in certain regions. The protein content of maize forage is low, so it requires a nitrogen supplement. Maize is used as forage in Burkina Faso, for instance.
This rather lengthy list of plants that have been tested as rabbit feed does not include every usable plant. There are such grasses as the various species of Digitaria, for example, though these are usually poor in protein. Where cabbage can be grown it should be added to the list. Cabbage is a traditional rabbit feed in France. Its 1720 percent protein content is fairly high.
Leaves of trees such as the mulberry could be a potential feed for rabbits. Trials have shown that rabbits will eat mulberry leaves but their nutritive value has not yet been determined. Ash leaves used to be a common feed on farms in France and are still used as feed in Algeria. They contain about 17 percent protein.
AGRICULTURAL AND INDUSTRIAL BYPRODUCTS
The various agricultural and industrial byproducts will not be reviewed here, as lists of byproducts and their composition are usually available for each region. Only a few need special mention. First of all the various tropical oilcakes, such as groundnut, already described, palm nut and coconut. Cottonseed cake should be used very prudently, as rabbits are at least as sensitive as pigs to gossypol.
Brewer's dregs and citrus pulp are possible feed sources, where the processing plants are not too far from the rabbitry. Rabbits can also be fed waste products from pineapple canneries, as in Ivory Coast, but pineapples are poor in protein.
Brewer's draff from the manufacture of barleybased beer and dolo dregs from millet beer can produce good results. In a test conducted in Burkina Faso, dolo dregs were used as 80 percent of a concentrate feed with 10 percent groundnut cake, 6 percent blood meal and 4 percent bone meal. This was fed with a forage supplement of green Brachiaria or dried groundnut tops. Local rabbits grew faster with this feed ( 104 g a week) than with an imported balanced concentrate feed (83 g).
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