Feeds and feeding under tropical conditions for rabbit

One of the advantages of production in tropical countries is that rabbits can be fed forages and agricultural byproducts not suitable for human consumption. In general, if available feedstuffs are suitable for poultry production, then it is more efficient to produce poultry rather than rabbits. The role that rabbit production can play is in the utilization of fibrous by-products that are useful neither for poultry nor swine, and of forages that may be available in insufficient quantities for ruminants. When these feeds make up the bulk of the diet for rabbits, 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 to 20 g per day, in contrast with the 35 to 40 g per day which is commonly observed in temperate regions. The lower result in the former case may be attributed to a number of factors, including heat stress as well as diet.

Only limited data are available on the nutritional value of tropical feeds for rabbits, and even less data exist on feeding systems and programmes. 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, Makhamvera and Kayange (1985) reported on the composition of a number of African forages that have potential as rabbit feeds. The tropical legume forages, in general, have a high content of digestible energy and protein, while the tropical grasses are characterized by an extremely low digestibility (see Table 2).

Thus, the selection of forages can be of major importance. In Indonesia, for example. producers have had very little success with the use of Setaria spp. as rabbit forage. Even though the grass would appear to be a suitable feed, it is almost completely indigestible (see Table 3). Tropical grasses have a cellular structure that resists degradation in the digestive tract. They also 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.

Many more data of the type shown in Tables 2 and 3 are needed on tropical feeds to allow recommendation of the most useful feedstuffs and to dissuade farmers from using forages that are very low in nutritional value.

Many tropical feeds contain toxicants and some tropical legumes contain toxic amino acids or alkaloids. Leucaena, for example, contains mimosine, while cassava contains cyanogens. By using 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. Raharjo et al. (1986a), for example, used a diet in which all of the protein and energy were provided by alfalfa meal and wheat milling by-products, and it was found that production of does over several parities was adequate. Because energy and protein needs are highest during lactation, a concentrate supplement could be used for lactating does, while the weaned rabbits could be raised 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 rancidity, which can reduce palatability, and care should be taken to avoid rancid rice bran in feed.

The amount of forage offered should be close to the amount voluntarily consumed. Fresh forage should be provided at least twice daily and the uneaten material removed before additional feed is offered to prevent spoilage. With palatable forages, the daily intake of fresh forage for a doe or weaned rabbits will be approximately 400 to 500 g per animal per day and the amount of concentrate offered should be approximately 50 g per animal per day. Either a purchased commercial concentrate or a home-made compounded supplement consisting of garden and table refuse may be used. In addition, rabbits require salt in their diet.

The palatability of forages is an important factor in rabbit production, particularly 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 for 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, such as setaria, brachiaria and elephant grass, were found to be less palatable than the legumes.

The leaves of trees in many areas can be used to provide forage in the dry season. Besides the tropical legumes mentioned previously, trees with potential for feeding include the mulberry (Morus spp.), 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.