How to control thermal stress in rabbits

What are the effects of thermal stress on rabbits? What actions should be taken in the event of hot weather?

Rabbit farming is a common practice in Africa that takes place on traditional farms as well as on more industrialised farms. Regardless of how they are structured, all these farms have to cope with thermal stress in rabbits, which means that the body is not able to maintain a normal temperature to ensure standard metabolic and physiological functions.

In rabbits, temperature-humidity combined together is more important than the temperature alone, because the humidity in the air modifies the temperature felt by the rabbits whose thermal neutral zone is set between 10°C and 25°C.

On farms, it is not always easy to control the ambient air quality. This is particularly true in Africa, where climatic conditions are sometimes extreme (see the table) and the temperature and humidity settings in livestock buildings are often difficult to adjust without appropriate devices (closed building, fans, cooling systems, etc.).

Detrimental effects of hot weather

High temperatures affect both the behaviour and performance of rabbits; therefore, close attention must be paid to these indicators of thermal discomfort.

• It may be possible to observe the following behaviours in rabbits: an increased respiratory rate, the blood vessels in the ears become larger (expand) and more visible and the rabbit may lay down as, by doing so, it can maximise the thermal exchanges.

• Thermal stress has repercussions on various zootechnical levels.

High temperatures, above 30°C, have a significant impact on feed intake, which can drop to 60%. This often results in decreased fertility and milk production in does, which leads to increased nest mortality of young rabbits. Reproduction of adult males and growth of young growing rabbits Male reproduction and growth during the fattening period are also affected.

Thus, the effects of thermal discomfort may be visible in the short term (decreased consumption, mortality, etc.), as well as the medium and long term (fatigued females, economic indicators, etc.).

Several actions to be implemented during hot weather

Certain concrete actions may help limit the impact of very hot weather on the behaviour, health and performance of rabbits.

Atmosphere

• Adjust the fans so that they remove the excess heat as well as the water produced by the animals. Provide an overhead extraction system in order to remove 30 to 40% of the air above the animals.
• Use “cooling” systems to cool the ambient air in the rooms; perform regular maintenance on them to maintain their efficiency.
• Mist the rearing room or, as a last resort, moisten the air inlets and corridors with clean water.
• On traditional semi-open or open-air farms, use fans (spraying water in front of the fan will create a misting effect) and avoid direct sun by providing shade for the rabbits using local materials around the building or cages (straw, shavings, cardboard, tarpaulin, etc.).
• When designing a building with natural flow ventilation, orient the building so that it takes the sun's rays and the prevailing winds into account so as to create a shaded and ventilated atmosphere (without strong air currents), and consider putting in a high roof so that there is more volume in the room.

Management approach

• Feed the fattening rabbits and breastfeed the young rabbits in the evening so that the extra heat produced by digestion takes place during the cooler hours.
• Increase monitoring during births in order to avoid births on the wire mesh.
• Decrease the amount of shavings and hairs in the nests and remove the nests a little earlier.
• Reduce densities during the fattening period.
• Plan to increase doe renewal.

Animals

• A recent study has shown the benefit of “trimming” rabbit hair to reduce the negative effects of high ambient temperature on the performance of growing rabbits. Although unusual, this practice could be used, during extreme conditions, on traditional farms that do not have the possibility of controlling the atmosphere.

Water

• Change the water in the troughs more often so that it stays fresh and does not stagnate.
• Flush the pipes regularly to prevent the growth of algae.
• Use soluble products to support physiological processes (preservation of the respiratory system, liver protection, vitamin C, etc.).
• On traditional farms, make sure to increase the number of water points.

Nutrition

• Adapt the feed specifications to compensate for the decrease in their feed intake (nutritional concentration) while increasing feed palatability.
• During the suckling period, increase the complementary feed intake so as to limit the under-consumption of complete feed as well as fatigue in breeding females and males

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