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MEKARN Workshop 2008: Organic rabbit production from forages |
Rabbits withstand cold climate and do not withstand hot climate. Hot summer climate threatens rabbit reproduction, growth and even endangers rabbits live. Traditional backyard rabbit farming are normally small in scale and flexible in operation. In summer, farmers would stop mating and breeding or even sell the breeding rabbits to avoid any risk. However, with the rabbit industry development in recent years in china, some large-scale intensive commercial rabbit breeding and processing enterprises like Kangda Food Company Limited, emerged for whom sustained market supply and cost efficiency are among top priority in management. Kanda Food Company breeds about 5000 thousand rabbits, with 120 thousand breeding animals. Such company cannot simply stop rabbit reproduction with seasons change. They must explore and apply, through technical innovations, a scientific management system for scaled rabbit production to ensure normal and safety rabbit reproduction and prevent heat stroke to their production. Efforts targeted at establishing a scientific management system for rabbit breeding in hot climate have been very promise to solve this problem.
Different with other livestock, rabbit has no developed body sweat gland except that on lip and groin, so that it is very difficult for rabbits to depend on skin to do heat dissipation. While the external temperature rises, rabbit can only accelerate heat dissipation by expanding the blood vessel to increase blood flow and the breath frequency. Breathing becomes the main heat dissipation approach of rabbit. When the external temperature rises, rabbit would accelerates breathing frequency for heat dissipation by moisture evaporation, to maintain thermostasis. When the external temperature rises from 200C to 350C, the breath frequency of rabbit will increase from 40 times to more than 200 times per minute and the rabbit live temperature reaches 430C. However, the ability of heat dissipation by breathing is still very limited, and the sustained high external temperature can lead to continuous polypnea of rabbit and affect seriously its health. When the room temperature reaches over 300C, the reproductivity declines obviously. When the room temperature reaches 350C, the rabbits mortality rate rises.
Under high external temperature, rabbit may exhibit heat stress. With breath frequency increasing, it breaths out large amount of CO2, with blood pH value rising sharply, which leads to the respiratory alkalosis, and it will also lead to the running off of body K+, the maladjustment of electrolyte, the collapse of body physique, which endangers rabbit life.
High temperature resulted in decreasing of feed intake of rabbit, resulting in weakening of body physique and disease resistivity and reducing of survival rate. Rabbit feed intake may reduce 30 ~ 50% from heat sensitivity. Especially the nursing does will exhibit serious emaciation ,milk deficiency, which not only affects the health itself, but also affect the growth of their young . Even though they can be able to tide over the high temperature climate, it also leads to high ablactating death rate because of the bad basis of prophase lactation. By comparison in practical production, ablactating survival rate and breeding survival rate during hot summer season is 20% lower than that in other seasons, and ablactating live weight is 300 grams lower at least (Tab 1).
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Table 1: Impact of high temperature to meat rabbit production |
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month |
Ablactating survival rate % |
Birth weight g/piece |
ablactating weight g/piece |
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Sep, Oct, Nov |
90.8 |
60.3 |
863 |
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July, August |
70.0 |
53.8 |
482 |
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Difference |
-20.8 |
-6.45 |
-381 |
High temperature affect the sexuality and sperm quality of bucks, resulted in reducing the conception rate and utilization ratio of breeding rabbits, and in prolonging the empty days and the production cost will be increased. When temperature reaches over 300C, sperm motility of the bucks reduces obviously, with complete die sperm or large number of abnormal sperm. When the temperature reaches 350C, the bucks loses sexuality.
While rabbit body physique is getting poor under high external temperature, pathogenic microorganisms propagate swiftly under high temperature and high humidity, rabbits are susceptible to diseases.
Measures for cooling down in sheds
The rabbit shed's span of large scale commercial production is normally between 10 to 12 meters with relatively high stock density, resulting in poor ventilation and sweltering. The results is remarkable through longitudinal ventilate in decreasing temperature for these sheds, with the fan installed on one side of the shed. When the temperature reaches over 300C, all windows should be sealed up, the fan starts operating for exhaust ventilation. The advantage of forced-air cooling is that it will blow out the animal heat and the moisture air in the shed, their disadvantage being high energy cost which is not economical for small farms.
For rabbit sheds located at inland area with hot and dry climate, installation of water screen combined with longitudinal ventilate can lower shed temperature from 50C to 70C. The advantage of water screen is that it can lower the temperature effectively and purify the air with disinfectant added in the circulating water. The disadvantage of water screen is that it may leads to high humidity that increases coccidiosis and colibacillus infection cases. Another disadvantage lies in the increased energy cost.
It is an effective measure to spray daily deep well water to the roof of the rabbit shed during high temperature time by installing a water-pipe on rabbit shed roof with shower nozzles installed by width of the rabbit shed. Water evaporation will lower the temperature by moisture evaporation.
For simple complete open-sided rabbit housing, it is recommended to build rabbit sheds in the wood or plant fast growing trees between rabbit sheds to keep off direct sunlight and ensure natural ventilation with satisfactory result to lower high humidity high temperature. For semi- open sheds, it is recommended to plant vine which will climb on the top surface of the sheds to keep off direct sunlight and prevent heat conduction.
Measures to improve feed nutrition formulation
Under high temperature, the rabbits lose appetite, reduce feed intake, owing to heat stress, resulting in rabbit undernutrition and prostration, oestrous rate reduction of does and sexuality diminution of bucks. It is not workable to force rabbits to increase feed intake. The only way is to adjust feed formula and increase the energy level of unit feed to satisfy rabbit energy requirement from less feed. In practice, we add appropriate amount of vegetable fat in diet, in substitution of some carbohydrate. Adding 3% vegetable fat to the diet would relieve the rabbit from heat stress. The high unsaturated fatty acid content in vegetable fat helps to achieve better effect in high temperature season. The energy level of rabbit diet should be about 10.2 MJ per kilogram in spring and autumn season. The amount of rabbit feed intake in summer accounts for only 60 % to 70% of that in spring and autumn season. By increasing the energy level to 11.5 MJ per kilogram in summer, better effect will be achieved for reproduction. The experiment by the author in summer time demonstrates that, under normal reproduction condition in summer, with the energy level in diet reaching 11.5 MJ per kilogram, the live weight of the nursing does at 30th day of nursing, with a litter of eight young she nursed, only lost 5% to compare with its live weight at 1st day after kindling.
High temperature will lead to week digestion of rabbit. Adding green forage will help increase cellulose and vitamins in digestive tract, improving rabbit digestion and appetite in high temperature season.
Reduced feed intake of rabbit in high temperature climate will lead to insufficient protein level. Crude protein ratio in diet should be maintained between 16-17%. Increasing essential amino acid (methionine, lysine) to proper level will help to balance daily diet.
Reduced feed intake will cause insufficient vitamins and microelement intake, leading to depressed resistivity to heat stress. Adding proper portion of vitamins and mineral matter in diet will help rabbit to resist heat stress.
Add anti-heat stress additive in feed or water in order to adjust the inner electrolyte balance and enhance the resistivity.
High temperature can cause inner electrolyte balance disorder of the rabbit, so it needs to add the electrolyte to relieve rabbit from heat stress. With the heat stress reaction, H+ concentration reduces, which leads to blood pH value rising and breath alkalosis. By adding 0.1% ~ 0.3%, baking soda in feed, the pH value in blood will decrease, anti-heat stress of rabbit will be released to a satisfactory degree. Adding 0.2% ~ 0.5% KCl in drinking water would meet the potassium requirement of rabbit.
The most sensitive and obvious phenomenon of rabbits of heat stress is shown by hyposexuality and low sperm quality, low conception rate, so that a great number of rabbitries would stop reproduction in summer, which inevitably increases the feeding cost and decreases the utilization ratio of breeding rabbits. Based on our practical experience, following measures could ensure regular mating and reproduction in summer, ideal output target can be guaranteed.
During high temperature days with temperature exceeding 30~C, the breeding bucks should be caged in such area in rabbit shed where free giving air-vent is available. Air-conditioning special for breeding bucks may be installed, the breeding bucks would maintain energetic with regular sperm quality, normal mating and reproduction will be guaranteed. If artificial insemination being adopted, this measure is especially worthwhile.
Heat stress also reduces the oestrus rate of does to a great extend. To ensure the high oestrus rate of breeding does in high temperature climate, contrast tests with different methods have been conducted in Kangda Food, including hormone treatment and different drug treatment. The best result is with the inducing oestrus. Mating after inducing doestrus for 48 hours, more than 80% of the breeding does undergo oestrus. A small number of does that do not undergo oestrus have actually exhibit ovulation. Therefore they should also be mated, their conception rate would be very close to that of the breading does in natural oestrus.
Even though small-scale rabbitry may stop reproduction in high temperature season, they still face the problem of how to care the kitttens in the lay-box in stock when the high temperature season comes. The large scale intensive rabbit farms do not stop reproduction in hot summer season and the number of kits in stock would be even more. During this hot period, the breeding does would reduce feed intake ,with their physique condition getting weak, and their body weight getting lost, the milk getting insufficient, and heat stress also makes the breeding does remarkably inattentitive to their young. Further more, high moisture and high temperature are contributing factors in illness. All these will endanger the growth of the kits, resulting in low ablactating weight, weak physique, small size and increased mortality of the whole litter. The following measures are proved to be effective to ensure survival rate in high temperature season
More than 3000 litters of kits were observed and analyzed from which comes the conclution that to keep average eight kits in each litter in spring and autumn is most suitable. However, the ablactating weight and ablactating survival rate will be reduced obviously if keeping the same number in summer. The ablactating weight and ablactating survival rate will increase if keeps average seven kits in each litter. Considering the breed characteristic in high temperature season, reducing the number of average number of kits in each litter would increase the quantity and quality of the rabbit for sale.
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Table 2: Comparison of baby rabbit number/ litter & weaning numbers in high temperature season |
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average kits per litter |
months |
Weaning survival rate (%) |
weaning number per litter |
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8 |
Sep, Nov, Dec |
90.8 |
7.84 |
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8 |
July |
70 |
5.6 |
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6.8 |
Aug, Sep |
85 |
5.78 |
High temperature and high humidity contributes the factor of outbreak of coccidiosis and other digestive disease. According to our statistics, 80% of mortality of rabbits in 40~70th day from July to August is caused by coccidiosis infection and secondary digestive infection caused by coccidiosis. The following preventive measures are proved to be effective to reduce losses by experiments.
That can restrain the propagation of harmful bacterium, improve the environment of intestines and the immunity of the animal to decrease infection of intestines disease. In high temperature season, rabbit will double the drink, resulted in increased moisture in its intestines which will cause diarrhea of pH value and bacterium maladjustment. Adding tiny organism's preparation will help to adjust the balance of bacterium in intestines effectively and relieve the animal from heat stress.
Mould is active in summer. Feed safety management should be enhanced for the whole feed chain from raw feed material to feed processing, preserving and feeding as well as ingesting of rabbit. Rabbit are very sensitive to mould and mildew toxin. Mould exists widely in most feed raw materials with rapid reproduction. Mildew toxin can lead to shedding of the cecum mucous membrane and anaerobism inner cecum, which would lead to the outbreak of Clostridieum welchii, with mortality rate as high as 30% ~ 80%. Rabbit breeding industry suffered great loss with the outbreak of mildew toxin infection every year. Nearly every large scale, intensive rabbit farm suffered from this disease by different degree, with some farms suffered many times a year. Furthermore, the TMR technology of rabbit feed is just underway and the anti-mould technology is not as advanced as poultry feed industry and pig feed industry, which increased the breeding risk for rabbit industry.
In high temperature seasons, microorganisms propagate swiftly. Disinfecting flow chart and benchmark disinfecting is necessary to ensure a safe and purified environment of rabbit sheds to prevent rabbit from infection.
Chemical disinfecting with operand, quatermary amine salts, acids and phenols antiseptics should be applied regularly, and the chemicals should be changed accordingly to different diseases.
Dilute disinfectant strictly according to the stipulated ratio; clean rabbit houses and fields before disinfecting and careful and thorough spraying requirement is to be observed.
Spray-disinfecting rabbit houses no less than twice a week; wash clean and flame disinfecting cages once every 49 days; spray-disinfecting production field with 2% NaOH at least once a week; keepers must wash hands and disinfecting hands with alcohol before entering rabbit sheds. Rabbit seat plate or cushion and equipment must be washed clean and steeped in disinfectant.
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