Rabbit project planning
strategies for developing countries
(2): Research applications
S D Lukefahr* and P R Cheeke**
*International Small Livestock Research
Center, Department of Food Science & Animal Industries,
Alabama A&M University, P.O. Box 264, Normal, Alabama 35762
**Rabbit Research Center, Department of Animal Science, Oregon State University,
Corvallis, Oregon 97331-6702 (USA)
A marked rise in rabbit project development activities throughout the developing countries has been observed within the past 10 years. This global response may be attributable to an increased awareness of the potential of small-scale rabbit production for the world's majority of subsistence rural and peri-urban inhabitants. There is a tremendous need for descriptive data of rabbit populations. Fortunately, relevant economic, nutritional and sociological parameters associated with rabbit production are now becoming available from certain developing countries, such as China, Egypt, Indonesia, Mexico, Nigeria and Tanzania. Available technical information from developed countries in many instances is not appropriate to locally specific conditions represented in many developing countries. Applied research conducted in developing countries on vital aspects of rabbit production: breeding and genetics, disease control, economics, housing systems, management, nutrition and reproduction, is urgently needed in order to ensure a high potential success rate for rabbit development projects, in terms of achieving favorable economic, nutritional and sociological impact.
Key words: rabbits, family farms, tropics, subtropics, genetics, health, forages, environment, housing, development.
It is generally regarded that rabbits were first introduced into many developing countries by colonial settlers and missionaries. Conventional captive meat rabbit production largely represents, therefore, a relatively recently introduced small livestock activity in many countries in the Third World.
While applied and basic rabbit research conducted in developed countries has yielded numerous reports in the scientific literature, research reports on the various production aspects of rabbit production are limited from the lesser developed countries (LDC's). Results of studies from non-LDC's are generally not appropriate for tropical production systems because environmental factors (eg: climate, diet, housing and management) and genetic stocks relate only to what is typically found in temperate regions.
In order for rabbit development projects in LDC's to be successful, it is imperative that more research be done whereby locally specific conditions, such as economic, social, breeding stock and forage resources, are taken into account.
The purpose of this paper is to address local technology issues and suggest appropriate research which could advance the role of the rabbit as a beneficial agricultural species.
Suitable breeds and selection practices
The progenitor of the domestic rabbit (Oryctolagus cuniculus) is believed to have evolved in the Mediterranean region, extending later into the Middle East and North Africa. Beyond this restricted global area, the rabbit may be truly considered non-indigenous. In general, two types of rabbit can be found throughout the developing world: local strains and "improved" exotic breeds. Local strains, such as the Criollo in Latin America, the Japanese Large White and Sichuan White in Asia, and the Baladi in the Near East and North Africa, may have existed in these geographic regions for decades, even centuries. In most cases they represent an introduced food species, not truly indigenous. For the local strains it is possible that a marked extent of genetic adaptation to a unique environment has gradually occurred over generation time. Such valuable germplasm resources should be properly conserved through government policy. In cases where local strains are in danger of extinction, immediate efforts should be made to preserve such genetic stocks (Lukefahr 1988a).
One highly typical observation of many local strains involves the apparent small body size and low productivity. This may be explained on genetic grounds by: (1) original introduction of small, lowly productive stock; (2) natural selection and (3) absence of artificial selection for increased productivity, or some combination thereof. The first point is straightforward, while the second point implies natural selective advantage for small body size and/or decreased productivity to genetically conform to an adverse environment. Absence of artificial selection refers to a basically non-existent selection program for increased meat producing capacity. Other operative factors, of both genetic and environmental origin, may be involved.
A second general impression is the seemingly wide genetic variability, detected at the phenotypic level, within many local rabbit strains for such characters as coat color, body conformation and size and production. In Cameroon, one local strain expressed some eighteen different coat colors and/or patterns, as observed by the first author, which perhaps reflect the original crossings of several distinct rabbit breeds prior to or following initial introduction to the country. In addition, the presence of important levels of heterosis, favorably affecting performances, may potentially exist, especially where the local strain represents a composite of several original breeds. This specific genetic effect may enhance greater physiological capacity for successful environmental adaptation. Furthermore, heritability levels could, in effect, be significantly increased, according to genetic theory.
While reports to confirm such hypotheses are not conclusively available in the literature, if such wide genetic variability indeed exists within certain local strains for production traits, there would appear to be ample opportunity for achieving impressive genetic progress through applied selection.
Simultaneous genetic improvement for both local adaptation and production characteristics could conceivably be set as the primary breeding goal for government breeding stations and large private rabbit farms. Table 1 provides pertinent information on reported heritability estimates for various production traits in rabbits.
Selection emphasis should be applied to traits of moderate to high heritability, such as individual growth and carcass-related traits. For lowly heritable traits, such as litter size and survival, baseline culling levels (independent culling technique) for low average record productivity should be established.
Unfortunately, a widely observed practice is the indiscriminate crossing of breeds on the unfounded notion that local breeds are genetically inferior. A serious consequence of this practice is the possible loss of local germ-plasm and lowered productivity of imported breeds due to unsuccessful environmental adaptation. In probably all cases, breed evaluation tests (local vs exotic stocks) should be conducted prior to widespread distribution.
Numerous exotic breeds of rabbit have rather recently been introduced into many developing countries. Perhaps the most common imported breeds are the Californian, the Chinchilla, the Flemish Giant and the New Zealand White. Although some decline in fertility has been observed, in general, many exotic breeds of rabbit have been observed to perform relatively well under a diversity of environmental conditions (IFS 1978; Campos et al 1980; Carregal 1980; Damodar and Jatkar 1985), as long as proper feeding, housing, management and health measures were consistently practiced. For the purpose of breed comparisons across broad regions of the developing world, limited data on only two breeds - Californian and New Zealand White - are reported in the scientific literature. Both commercial meat breeds would appear to be potentially suitable for most environments. More basic research is needed in order to make major recommendations as to the appropriateness of certain breeds in specific environments. Currently no breed of rabbit can be universally recommended.
A popular animal breeding practice used in many developing countries is simple upgrading. This involves successive generations of matings of an exotic breed to the locally available strain to increase the proportion of exotic breed inheritance. The early generation crosses may perform better than the local parental strain, in terms of annual meat productivity. For this reason some rabbit projects prefer to distribute crossbred stock to farmers.
|Table 1: Heritabilities of production traits in rabbits|
|Fertility and litter size|
|- Litter size born alive||2.1||Lampo and Van Den Broeck 1975|
|3.0||Rollins et al 1963|
|- Litter size weaned:||28 days||15.0||Matheron and Poujardieu 1984|
|56 days||0.0||Rollins et al 1963|
|- Enteritis and Pneumonia deaths|
|. to 56 days of age||12.0||Rollins and Casady 1967|
|- Survival to 56 days||6.0||Harvey et al 1961|
|- Maternal behavior (nest building)||24.0||Berovides and Fernandez 1982|
|- Milk production||31.0||Patras 1985|
|45.5||Randi and Scossiroli 1980|
|- Average weight per rabbit:|
|21 days||36.0||Leplege 1970|
|56 days||65.0||Leplege 1970|
|- Total litter weight:|
|56 days||0.0||Rollins et al 1963|
|56 days||22.0||Lukefahr 1982|
|-- adjusted for litter size||69.4||Lukefahr 1982|
|- Body weight:||1 day||40.0||Bogdan 1970|
|30 days||17.0||Rouvier 1981|
|56 days||22.6||Mostageer et al 1970|
|60 days||54.0||Patras 1985|
|- Rate of gain:|
|30-70 days||44.0||Rouvier 1981|
|- Feed consumption:|
|30-70 days||32.0||Vrillon et al 1979|
|- Feed efficiency:|
|28-77 days||34.0||Baselga et al 1982|
|- Loin width:||56 days||60.0||Bogdan 1970|
|- Dressing percentage||60.0||Fl'ak (1978)|
|- Hot carcass weight:|
|70 days||61.0||Poujardieu et al 1974|
|70 days||36.0||Rouvier 1981|
|- Meat:bone ratio (hind-leg)||49.7||Varewyck et al 1986|
|- Weight of hind-leg meat||60.0||Fl'ak 1978|
* Source: Complete references cited by Lukefahr (1988b).
From a genetic standpoint, exceptional crossbred productivity, if real, may be attributable to favorable additive and maternal breed effects, heterosis, and/or other more complex forms of gene action. Such improved varieties may be developed into new synthetic breeds of rabbit where capable genetic expertise and related resources are available. To date, an improved breed of rabbit genetically developed under tropical conditions does not yet exist. Research in this promising area is strongly warranted. More sophisticated systems of crossbreeding, such as rotational and terminal crossing, while being more widely practiced in commercial operations in developed nations, are not presently feasible in many instances in developing countries. Furthermore, such advanced systems entail various sectors in the commercial rabbit industry, such as seed- stock and hybrid stock companies, which do not generally exist in developing countries.
In terms of practical stock selection, farmers may avoid undesired inbreeding through routine exchange of herd bucks with other farmers. Selection of offspring from consistently productive and healthy parental stock is recommended to farmers. This involves the regular keeping of basic pedigree and production records. In addition, simple financial records should be maintained.
The current demand among farmers and other project recipients for quality breeding stock in an LDC may be great. In some cases, national or regional rabbit breeding centers (governmental and private) presently provide this valuable service in several developing countries.
Feeds and feeding under tropical conditions
One of the advantages of rabbit production in tropical countries is that rabbits can be fed forages and agricultural by-products that are not suitable for human consumption. In general, if feedstuffs are available that are suitable for poultry production, it is more efficient to produce poultry with these feeds than rabbits. The niche that rabbit production can occupy is in the utilization of fibrous by-products that are not useful for poultry, as well as swine, and forages that may be available in insufficient quantities for raising ruminants. When these feeds make up the bulk of the diet, the use of a small quantity of concentrate feed to improve performance can be justified.
The growth performance of rabbits in studies reported from tropical countries is generally in the range of 10-20 g per day, in contrast to 35-40 g per day commonly observed in temperate regions. Probably a number of factors, including heat stress, are involved as well as diet. An interesting study would be to determine the production of rabbits of the same breed in various tropical locations when fed the same diet as used in American or European studies, to determine the degree to which the poorer performance can be attributed to environment.
Only limited data are available on the nutritional value of tropical feeds for rabbits, and even less data exist on feeding systems and programs. The most extensive compilation of nutritional data on rabbit feeds is that of Raharjo (1987), who evaluated a number of Indonesian forages and agricultural by-products. Ayoade et al (1985) reported on the composition of a number of African forages with potential as rabbit feeds. In general, the tropical legume forages are higher in protein and lower in fibre than the tropical grasses, and are much more digestible (Tables 2 and 3).
|Table 2: Composition of tropical forages (% dry matter basis) (Source: Raharjo et al 1986a).|
|Manihot esculenta (tops)||4804||16.8||28.2||38.9||1.76||0.28|
* Panicum maximum cv Green Panic.
** Panicum maximum cv Guinea.
It is clear from these data that careful selection of forages is an essential first step in developing suitable feeding systems. In Indonesia, for example, producers have had very poor success with the use of Setaria spp. as rabbit forage, even though the grass appears visually to be a suitable feed. The explanation for the poor results is that it is almost completely indigestible (Table 3). Tropical grasses have a cellular structure that resists degradation in the digestive tract; they have a high content of poorly digested constituents such as vascular tissue, parenchyma bundle sheaths and epidermis, and a low content of the more readily digested mesophyll cells. Much more data of the type shown in Tables 2 and 3 are needed on tropical feeds to allow the recommendation of the most useful feedstuffs, and to guide farmers away from using forages that are of very low nutritional value.
|Table 3: Digestibility of tropical forages in rabbits (Source: Raharjo et al (1986a).|
|----------------- Apparent digestibility(%) -----------------|
|Manihot esculenta (tops)||49.9||47.0||42.0||25.6||33.0|
* Panicum maximum cv Green Panic.
** Panicum maximum cv Guinea.
Many tropical feeds contain toxic substances. Some of the tropical legumes contain toxic amino acids or alkaloids (eg: leucaena contains mimosine while cassava contains cyanogens). By the use of a mixture of forages, the concentration of specific toxins can be kept to non-hazardous levels. Thus potentially valuable feeds such as leucaena can be utilized as components of forage mixtures.
Rabbits can be raised successfully without the use of grain in the diet. For example, Raharjo et al (1986b) used a diet in which all of the protein and energy were provided by alfalfa meal and wheat milling by products, and found that production of does over several parities was adequate. Because energy and protein needs are highest for lactation, it might be desirable to use a concentrate supplement for lactating does, and raise the weaned rabbits entirely on forage and agricultural by-products such as wheat bran or rice bran. Rice bran is an excellent energy source for rabbits (Raharjo 1987), and is available in large quantities in many developing countries. However, it is susceptible to development of rancidity, which may reduce palatability. Care should be taken to avoid rancid rice bran in rabbit feeding.
The amount of forage offered should be adjusted to be close to the amount voluntarily consumed. It is desirable to provide fresh forage at least twice daily, with the uneaten material removed before additional feed is offered to prevent spoilage. With palatable forages, the daily intake of fresh forage of a doe or weaned rabbits will be about 400-500 g per animal per day. The amount of concentrate offered should be about 50 g per animal per day. Either a purchased commercial concentrate or a home-mix, compounded supplement consisting of garden/table refuse may be used. In addition, rabbits require salt in their diet.
The palatability of forages is important in rabbit production, particularly in situations when the forages are expected to provide a major part of the daily nutrient intake. Raharjo and Cheeke (1985) and Raharjo (1987) evaluated a number of Indonesian forages in feed preference tests. In general, tropical legumes were preferred over grasses and agricultural by-products, with the exception of gliricidia (Gliricidia sepium), a legume which proved to be unpalatable. Leucaena (Leucaena leucocephala) is a very palatable feed to rabbits, even though it contains the toxic amino acid mimosine. Erythrina (Erythrina lithosperma), another legume, was well accepted. Sweet potato vines were palatable to rabbits in the study of Raharjo (1987), while banana and papaya leaves were poorly accepted. Most of the grasses (eg: Setaria, Brachiaria, elephant grass) were less palatable than the legumes.
Tree leaves can be used in many areas to provide forage in the dry season. Besides the tropical legumes previously mentioned, other trees with potential for feeding include the mulberry (Morus spp.) which is used in India, Brazil and Costa Rica as a forage, and black locust (Robinia pseudoacacia), grown extensively in China for rabbit feed. Ramie is utilized in Brazil, where it is considered a highly palatable and nutritious green feed for rabbits.
Much further research is needed on the nutritional and feeding value of tropical feeds for rabbit production, and the development of optimal feeding systems. Cheeke (1987) has summarized the current information available on the nutrition and feeding of rabbits under temperate and tropical conditions.
Disease control measures
One distinct attribute of rabbit farming is the relatively low incidence of epidemic diseases when a high standard of hygiene and careful management is practiced (IFS 1978). Rabbits do not require routine vaccination or medications to prevent or treat certain diseases. This is an important aspect since in other livestock species the lack of proper drugs is sometimes recognized as a major constraint to successful production.
When a disease does occur local remedies can often be effectively used as treatment. For example, one common disease condition referred to as ear mites (caused by an external parasite, Psoroptes cuniculi) can both be prevented and treated by applying drops of an oil-kerosene solution directly inside the ear canal. Vegetable oil, red palm oil and even clean engine oil may be used. In control of digestive disorders, such as diarrhea and constipation, various medicinal herbs and greens used in Cameroonian tribal cultures have been observed to provide similar therapeutic results in rabbits (Lukefahr and Goldman 1985). Other diseases or maladies, such as abscesses, cannibalism, skin mange and warbles, likewise have been inexpensively controlled using proven local measures.
Owen (1976) observed an apparent trend of lower disease incidence and/or higher productivity levels in rabbit operations managed as small-scale family units as opposed to intensive, commercial units. Management quality per animal may be less in large operations, and the close confinement situation may also impose greater likelihood of rapid disease outbreak, particularly concerning myxomatosis and pasteurellosis. It is imperative, therefore, where large central rabbit operations exist that stringent levels of hygiene and culling of diseased animals, as well as implementing proper quarantine measures, be maintained.
Two diseases of major global concern to rabbit production are coccidiosis and pasteurellosis. While coccidiosis can largely be prevented and treated, this disease often goes undiagnosed to the point where serious physical injury occurs -- liver damage and severe weight loss. Raising rabbits on the ground aggravates the problem due to more direct exposure to the infectious agent. Various sulpha-based drugs have shown good results in controlling rabbit coccidiosis (Aduma 1978). Sanitation is a critical determinant in the control of episodic frequency and morbidity levels due to coccidiosis outbreaks.
Pasteurellosis is a bacterial disease (Pasteurella multocida) which affects nearly all body tissues. Signs of the disease include mucopurulent nasal discharge, pneumonia, dermal abscesses, conjunctivitis, infertility and death. Only limited success is noted with treatment using broad-spectrum and sulpha based drugs. Moreover, only a culture test can confirm definitive exposure to Pasteurella. In well managed rabbit herds, however, the disease may rarely be a problem. Currently, the best means of controlling pasteurellosis is achieved through proper housing design, strict culling of infected animals and/or selection of healthy stock and quarantine. Some laboratories and universities have developed specific pathogen-free (SPF) stock which are pasteurella-free; projects have in some cases established rabbit populations through SPF stock importations. General guidelines of rabbit stock importation, with regard to disease control and sound genetic resource utilization, are highlighted in Table 4.
Table 4: Importation guidelines for successful stock introduction
1. Obtain breeding stock from highly productive commercial sources.
2. Stock certified disease free by licensed veterinarian.
3. Conduct culture test for Pasteurellosis.
4. Treat stock for coccidiosis according to drug dosage recommendations and precondition stock onto a fresh forage-based diet, prior to shipment. Avoid stock from a viral hemorrhagic disease area.
5. Procure documentation of health certification.
6. Ensure broad genetic base per breed (minimum of 15 bucks and 25 does included in shipment).
7. Shipment involves young virgin stock, ideally 3 to 4 months of age. Stock should be shipped during the most favorable season to avoid undue stress.
8. Delay breeding approximately 2 months after time of arrival at point of final destination.
9. Maintain high level feeding and management, including stock quarantine.
10. Closely monitor individual record performances to assess relative adaptation.
11. Retain adequate supply of young replacement stock.
12. Select progeny from proven adapted and productive parental stock.
Pasteurellosis has been detected in certain rabbit projects in developing countries where the common opinion of project managers was that the original imported stock introduced the disease. In one major rabbit project in China, some rabbits were observed as having expressed various outward signs (eg: sneezing, nasal discharge and matted inner forepaws) of a seemingly rare respiratory disease; a team of veterinarians was perplexed as to the definitive cause of the disease. A rabbit specialist consultant later recognized the disease as a classic case of pasteurellosis (Milne 1982). Unfortunately, this scenario has repeatedly occurred in several other countries.
A recent paper from China by Xu et al (1988) reported on the serious outbreak of a new viral disease ("rabbit hemorrhagic disease virus - RHDV") which has become manifested in parts of Asia and Europe, and most recently in North America. The body organs, especially lungs, liver and spleen, are severely affected. To date, no effective treatment is available since the immunological mechanism is not understood. Strict quarantine measures to control further spread of this disease are now underway (Patton 1989).
Throughout the world - developed and developing - there is a great need for veterinarians and extension field workers to become more familiar in the diagnosis, prophylaxis and treatment of rabbit diseases in regions where rabbit projects or enterprises exist. There is an urgent need for applied research in these basic areas of rabbit pathology.
Environmental and housing systems
Like other livestock species, rabbits need protection from adverse environmental conditions, including protection against predators. While ample sunlight and ventilation are important, either of both extremes may well limit production. Air quality is of major concern in the control of respiratory diseases, such as pasteurellosis and pneumonia. Ambient temperature and humidity levels, likewise, are particularly relevant to tropical or arid environments.
Under controlled experimental regimens, Stephen (1981) and Poujardieu and Matheron (1984) investigated varying temperature and humidity stress effects on growth and feeding performances of rabbit fryers. Stephen (1981) observed optimal productivity at 18°C (as compared with 5 and 30°C) and 70% humidity (compared with 60 and 80%) of 37.4 g average daily gain and 4.23 feed efficiency values. Poujardieu and Matheron (1984) reported that changes in temperature and humidity levels were additive on growth response, and that there were no compensatory gains due to previous environmental stress encounters.
It is well established that high ambient temperature can cause infertility in breeding rabbits, bucks being more sensitive than does. Rabbits are apparently more adversely affected by hot as opposed to cold climates. Prolonged exposure to a critical temperature in excess of 30°C is considered the threshold point at which infertility may result. A number of practical measures for alleviating heat stress have been documented by Cheeke et al (1987). Examples of such measures are providing cool water, ample shade, evaporative cooling, proper housing design and location, and usage of young and more potent bucks.
The rabbit's needs for basic shelter to sustain production are modest. It is fortuitous that the building materials required for construction of simple sheds, hutches, nest boxes, hay racks, and feeding and watering equipment are generally abundant in tropical developing countries. This attribute embellishes the overall low-cost feasibility of small-scale rabbit farming as an alternative enterprise (see Table 3 of companion paper by Lukefahr and Cheeke 1990).
Suitable shelter for rabbits might be an outdoor shed, veranda or empty room of the family compound, or a complete hutch (cage with roof and siding). Shed designs should be of narrow width (less than 6 m) with open sides to facilitate natural ventilation. The run of the shed can be of any length. The height of the shed can be designed to mimic a chimney effect to provide cooling through natural air movement (Cheeke et al 1987). The relative position of the rabbitry site should augment favorable environmental conditions. Rugh (1978) discussed several housing systems appropriate to Africa. In semi-desert regions where wood is scarce or costly, rabbit shelters can be constructed out of mud and thatch-grass as reported by Owen (1981). The rabbit dome concept - an underground earthen shelter which offers relief to high daylight temperatures - has merit in arid areas (Gentry 1983; Finzi et al 1988). Floor rearing systems of rabbit production, common to the Near East, however, are usually associated with increased incidence of parasitism (eg: coccidiosis) due to direct floor contamination.
Hutches can represent a variety of forms. Examples of durable and inexpensive building materials include bamboo, raffia palm, bush sticks, woven wood straps, bricks, mortar, etc., which have been reported throughout the developing countries (McNitt 1980; Owen 1981; Cheeke 1983; Lukefahr and Goldman 1985). Basically, each breeding doe unit requires a cage floor area of less than 1 m5, while each fryer unit requires from 0.05 to 0.10 m5. Regardless of the construction material used, the hutch should facilitate a comfortable and clean environment and be under the direct control of the farmer.
Accessory equipment: hay racks, nest boxes and salt, feeding and\ watering containers, can be fabricated from a diversity of products, including refuse items (bottles, cans and tins). Nest boxes made of wood, clay, metal and basket materials are useful in accommodating young litters. Generally, the nest boxes should be supplied with fine-stemmed grass hay, cotton, shredded paper, wood shavings, or other similar insulatory forms to enhance litter survival. Feeding and watering equipment must be readily accessible, voluminous and regularly sanitized. Clean water should always be available.
Rabbit losses due to predators and thieves can be a common threat to farmers. Usage of sturdy, well designed hutches, a protective fence, guard dog, close proximity of the rabbitry to the compound, installment of noisy items (eg: bells, chimes and gongs), spring-loaded rodent-traps, locks and native taboo deterrents are some examples of proven measures of control.
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(Received 15 September 1990)