by: Robert McCroskey, http://www.easterplanet.ca (previously published in Pan-American Rabbit Science Newsletter 2001, Volume 6(1), 18-20.)
Although being written from one of the few truly temperate climates in North America, this article provides some suggestions for raising and feeding rabbits in hot climates, or in the condition of increasing global warming, by integrating them with other land uses and making use of available agricultural by-products as feed.
Rabbits, like many other traditional farm animals are more suited to cooler climates, they have a low thermoneutral zone around 15°C., commence male sterility at 29°C., become severely stressed over 35°C. and have an average lethal ambient and rectal temperature at 42.8°C. (Harkness 1988, Marai 1999). However, there are possibilities to raise rabbits in hot climates that hinge on other properties of the rabbit, such as small size and their ability to utilize many agricultural byproducts in the feed.
The small size of rabbits and their relatively small space requirements compared to their ability to convert feedstuffs into meat, allows them to fit into areas not usually considered for agricultural production. It is this size and space factor that can allow rabbits to produce in hot climates.
No country regardless of how poor, can afford to waste the solar energy input that falls on their territory. Considering this proposition, along with the low thermal tolerance of the rabbit, it makes no sense to situate a rabbit barn in full sunshine and then try to keep the rabbits cool. Both the solar energy falling on the building along with considerable other energy input is wasted, in trying to generate a synthetic environment, a cost that rabbit production cannot carry. Therefore rabbit production units can and should be located under other productive uses, such as under the shade of date, nut or other trees, under factories or office buildings or residential buildings; or under banks of solar voltaic cells or some combination of these coverings. A rabbit facility can even be graded into a hillside with forage grown over it. A rabbit production unit located under a factory or office building can make use of the exit air from the building which normally has been chilled below the outside ambient temperature for human comfort. Another means of providing cooler air for the rabbitry is to bury large clay drain tiles underground and pull air into the building through the tiles. With the use of yucca extract in the feed, there is no objectionable odour that issues from a rabbit production unit and no major zoonotic diseases that preclude incorporating rabbit production closer to human occupations and housing. These factors help to integrate agricultural production into the urban environment, similar to previous discussions on the AWI (Area Wide Integration) E-Conference (see web site at http://lead.virtualcentre.org/en/frame.htm and click on AWI label).
With shortages of arable land, feed ingredients and water in many countries, rabbits can help with food production by converting many agricultural byproducts into meat. Generally, there is no need to use prime forages for rabbit feeding, and there is no need to use grains that are fit for human consumption. The list of what ingredients can be incorporated into rabbit feed is enormous and growing continuously, so only a few will be mentioned here, for instance: Berseem (clover) fibrous residue can be used at 18 or 36% of a corn-bran-barley-soy diet, while water hyacinth fibrous residues or beet pulp may replace 50% of alfalfa in such diets (El-Adawy et al., 2000); Full fat raw sunflower seeds can be used at 10% in the diet as a source of energy and protein (Abdel-Malak & Homouda, 2000); Barley radicle may partly replaced clover hay, wheat bran and soybean meal up to 30% of the diet (El-Gendy et al., 2000); Peanut hay can replace 100% of clover hay in rabbit diets (Ibrahim 2000a); autoclaved jackbeans can be used up to 28% in the diet, replacing 100% of soybean meal and about 50% of corn grains, while raw jackbeans can be used up to 14% of the diet, replacing about 50% of the SBM (El-Kelawy et al., 2000); Sugar beet tops can be used in the diet up to 10%, replacing part of the clover hay (Tag El-Din et al., 2000); Sweet potato tops can replace all of clover hay, at 30% of diet, and sweet potato roots can replace almost half the yellow corn, up to 15% of the diet (Ali Mervat et al. 1999); economical efficiency of feeding cassava root meal to growing rabbits from weaning and up to 16 weeks of age was considerably higher than that of barley (Abd El-Rahim et al., 1991); up to 40% acacia may be included in the diet of growing rabbits (Abdel-Samee et al., 1992).
There are some advisories on the feeding and diet formulation for rabbits in hot climates with most reports agreeing that higher protein level is beneficial (Abdel-Malak 2000, Zanaty & Ahmed 2000a, Ismail 1999, Taie & Zanaty 1993) but some other reports indicate that lower protein or variation of protein quality was more beneficial (Zanaty & Ahmed 2000b). Perhaps because rabbits adjust their feed intake not just to meet energy requirements but also to meet their protein requirements (Abdel-Malak 2000), excess protein could possibly be reducing feeding activity in hot periods. While making use of the various agricultural byproducts in rabbit feeding, care should be taken to keep the various carbohydrate fractions balanced according to the recommendations of Gidenne (2000).
Of highest concern is maintaining the activity of the rabbit except during times of actual heat stress, at which times they should be made as comfortable as possible with the least human disturbance. Personal observations of rabbit locomotion and behaviour indicate that because of the size and positioning of the caecum within the musculature of the rabbit, locomotion of the rabbit and caecal motility are intimately involved. If this is true, then a more active rabbit is more likely to remain healthy compared to an inactive rabbit.
Some factors which can improve activity of the rabbits:
1) Use adequate cage size. For fattening rabbits, the longest side of the cage should be no shorter than 90 cm. However, many rabbits can share this same cage due to the effects of stocking density, stocking density and cage size have been dissociated to some extent (McCroskey, 2000).
2) Slightly restrict feeding so that the rabbits are eager to eat; often such slight restriction of feeding will encourage more feed consumption than free-choice feeding because of eliminating the boredom effect.
3) Provide straw (barley, wheat or grass) at least once per day, 10 to 50 grams per cage. Provision of straw, which is the background of the rabbit's natural environment, allows them to chew (sharply cut) fibre particles to the size required by their digestive system (McCroskey 1999). Provision of straw also helps prevent boredom and inactivity in the rabbits, while maintaining familiarity with the environmental background construction material for their nests.
4) Provide toys for the rabbits, such as small used tin cans, and change the toys at least every week, to a different size or shape.
5) Generally countries with hot climate are also in short day length, so the extension of day length should be provided by means of a split-day lighting regime, adding the extra 2 to 3 hours of light per day during the night, centred around midnight. This gives a cooler time of the day in which to do feeding, handling, breeding, kindling (about an hour after the lights come on) and puts this energy consumption for supplementary lighting in an off-peak period of the day (McCroskey, 1996).
Abdel-Malak N.Y., Homouda I.A. (2000) Rabbit growth performance and some blood parameters as affected by using sunflower seed in their diets. Eygpt. J. Rabbit Sci. 10(1), 61-73.
Abd El-Rahim M.I., El-Gaafary M.N., Tawfeek M.I., Hoda E. Mohamed (1991) Growth, digestibility, blood constituents and reproductive efficiency of rabbits fed rations containing cassava root meal. Egypt. J. Rabbit Sci. Vol.1(1), 47-60.
Abdel-Samee A.M., El-Gendy K.M., Ibrahim H. (1992) Growth performance and some related physiological changes in rabbits as affected by feeding acacia under subtropical conditions. Egypt. J. of Rabbit Sci. Vol. 2(1), 13-22.
Ali Mervat A., Tag-El-Din T.H., Soliman A.M. (1999) Effect of sweet potato tops or roots in growing rabbit diets on growth performance, digestibility, carcass traits and economic efficiency. Eygpt. J. Rabbit Sci. 9(1), 13-23.
El-Adawy M.M., Borhami B.E., Abdel-Hamid A.E.Y. (2000) Utilization of sugar beet pulp and fibrous residues of Berseem and Water Hyacinth in feeding growing New Zealand White rabbits. Eygpt. J. Rabbit Sci. 10(2) 1-17.
El-Gendy K.M., Bassuny S.M., Shehata A.S., Sarhan M.A. (2000) Using radicel in animal nutrition. 3. growth performance, digestibility and carcass traits of growing rabbits fed different levels of barley radicel with or without methionine supplementation. Eygpt. J. Rabbit Sci. 10(1), 75-88.
El-Kelawy H.M., Abd El-Rahim M.I., Sarhan M.A., Rawia S. Amin (2000) Feed intake, reproductive performance, digestibility and blood metabolites in adult NZW rabbits fed diets containing raw or autoclaved Jackbean seeds (Canavalia ensilformis, L.). Eygpt. J. Rabbit Sci. 10(1), 157-173.
Gidenne T. (2000) Recent advances in rabbit nutrition: Emphasis on fibre requirements. A Review. World Rabbit Sci. 8(1), 23-32.
Harkness J.E. (1988) Rabbit behavior as related to environmental stress. J. Appl. Rabbit Res. 11(4), 227-236.
Ibrahim Sh. A. M. (2000) Clove and cinnamon as growth promoters and detoxificants against cadmium chloride in growing rabbits. Eygpt. J. Rabbit Sci. 10(1), 89-104.
Ismail F.S.A. (1999) Is there any beneficial effect to increase dietary protein for growing rabbits under high temperature conditions? Eygpt. J. Rabbit Sci. 9(1), 87-103.
Marai I.F.M. (1999) Intensive production of rabbits in hot climates. Pan-American Rabbit Sci. Newsletter 4(1), 14-24.
McCroskey R.A. (1996) Lighting programs - A review. Pan-American Rabbit Sci. Newsletter 1(1), 23-36.
McCroskey R.A. (Sept. 1999) Feed particle size and caecal function. Some new perspectives. In: 1st Int. Conf. on Indigenous vs Acclimatized Rabbits, El-Arish, Egypt, Sept. 7-9, 1999.
McCroskey R.A. (2000) Behaviour of the rabbit, A review. Pan-American Rabbit Sci. Newsletter 5(1), 18-31.
Taie H., Zanaty G.A. (1993) Effect of dietary energy to protein ratio on performance, digestibility and carcass quality of growing rabbits. Eygpt. J. Rabbit Sci. Vol. 3(2), 151-162.
Tag El-Din T.H., Al-Samra H. Abo-Egla, Ismail F.S.A., Samy S.S. (2000) Utilization of sugar beet tops in feeding rabbits. Eygpt. J. Rabbit Sci. 10(2), 223-238.
Zanaty G.A., Ahmed B.M. (2000a) Effect of different dietary protein sources and levels on growth performance, nutrient utilization and carcass characteristics of growing New Zealand White rabbits. Eygpt. J. Rabbit Sci. 10(2), 265-280.
Zanaty G.A., Ahmed B.M. (2000b) Effect of different dietary protein sources and levels on growth performance, nutrient utilization and carcass characteristics of growing New Zealand White (NZW) rabbits. Eygpt. J. Rabbit Sci. 10(2), 265-280.