How extreme temperature is affecting rabbit production in Nigeria

How extreme temperature can affect your rabbit’s production:

Heat is one of the most important climatic factors, which may affect rabbit production in Africa,  especially in Nigeria. The rabbit is very largely dependent on respiratory evaporation for the regulation of its body temperature and this confers only a limited power of adaption to hot climates. Heat is also dissipated by radiation and convection, but these are somewhat restricted by the rabbit's furry covering. Johnson et al..., (1957) reported that short hair and larger ears helped the cooling process in New Zealand White rabbits. According to these workers, growth and development were impaired at ambient temperatures of 28.3°C and above. Generally the higher the ambient temperature the greater was the disturbance of the rabbit's functions.

The temperature of a rabbit's body is best measured by recording rectal (Rectum-final section of the large intestine) temperature. A rectal temperature of 38°C is considered to be within the normal range. Lee et al., 1944 reported that at ambient temperatures above 29.4°C the rectal temperature begins to increase in the rabbit. When the rectal temperature of Angora rabbits reached 39.8°C, the animals became disinclined to move; at a temperature of 40°C they lay down on their sides; and at 41.7°C the rabbits suffered obvious distress but were able to carry out ordinary movements. These rabbits were found to be unable to tolerate ambient temperatures of 37.8°C to 43.3°C for more than 7 hours, within which time the critical rectal temperature of 41.7°C was reached.

Reproduction

There is evidence that high ambient temperatures can impair the reproductive performance of rabbits. In New Zealand Whites a temperature of 32.8°C reduced fertility in the male rabbits, a continuous high temperature being more detrimental than intermittent heat (Oloufa et al., 1951).

In the female, smaller blastocysts and embryos, and an increase in embryo mortality rates were also observed. El Sheikh and Casida (1955) concluded that the maximum 

temperature to which rabbits could be exposed (for 1 hour) without impairing health or sperm motility was 43.3°C at a relative humidity of 30 to 40%. Chou et al., (1974) heated the testes of live rabbits to 43°C for 20 min on three successive days. No spermatozoa were present in the seminiferous tubules up to 30 days after the treatment. However, recovery was complete at about 10-14 weeks following the treatment. Hiroe and Tomitzuka, (1965) observed a marked fall in semen quality in male rabbits subjected to ambient temperature of 30°C for 14 days. These changes in quality were associated with an increase in the pH of the semen, a fall in sperm motility, a decrease in sperm concentration, an increase in the percentage of abnormal spermatozoa and a decline in libido. These workers found that, with the exception of sperm concentration, the changes could be reversed by reducing the ambient temperature. Embryo survival was depressed by heat stress and this was more severe under constant heat stress than under fluctuating heat stress, and was due largely to post implantation losses.

Embryo survival at 12 days post fertilization was lower at 32.2°C than 21.1°C. Shah (1955) reported that severe prenatal losses occur in pregnant does exposed continuously in the first 6 days of pregnancy to environmental temperatures sufficiently high to cause a rise in body temperature of 1.2°C to 1.7°C. Such losses occurred through resorption of embryos following implantation. When laboratory rabbits were exposed to a Sahel- Sudanean dry climate, breeding was only successful for 5 months out of 12 (Tacher, 1970).

Heat has become an issue for breeders, especially in Nigeria as we are recording high temperatures in different parts of the country.

However, extreme temperatures can be tempered by different measures. Trees around the building decrease the amount of heat that enters during the day, by providing shade, and somewhat decrease the amount of heat that escapes during the night through radiation. They also lessen the impact of wind and rain (figure 6 and figure 7). Some fast growing legume trees include Leucaena, Gliricidia, Sesbania, Erythrina, and might even provide some feed for the animals. Besides trees, the roofing material greatly influences the heat inside. Use your own judgment:

corrugated iron is hotter than a straw, grass or tile roof (especially if the roof starts to become rusty).

Roof material and construction in relation with temperature