SALAMI, Saheed Ayodeji
University of Ilorin, Ilorin, Nigeria.
Climatic elements have direct effect on the system of animal production, body physiology and animal behaviour, feed supply and quality, proliferation of pests and parasites as well as preservation of animal products (Samson et al., 2011) A number of climatic elements such as temperature, rainfall, humidity, radiant energy, air movement, light, altitude etc. greatly influence and interact with the performance of livestock production. Similarly, they also cause major effects on animal physiology, behaviour and productivity through their individual or separate effects but, more often, by their combinations with other environmental factors. The influence of climate on animal production (including animal body functions, behaviours and productive abilities) may be direct or indirect. In either way, systems of animal husbandry or management are also affected. Direct influence of climate on animal production and husbandry has to do with such influence on the animal itself, while indirect influence is on the animal’s environment each of these shall be examined closely.
The over-riding environmental factor affecting the physiological functions of domestic animals is temperature. Temperature is measured using the instrument called thermometer, which are of various types. All domestic animals are homeotherms or warm blooded. In other words, they maintain their body temperature within a range most suitable for optimal biological activity. The body temperature range is relatively constant and is higher than the environmental temperature. The ambient temperature on the other hand varies with changes in the climatic elements at a particular time. The animal body temperature ranges within certain limits defined as the ‘Comfort Zone’ is a temperature range within which no demands are made on the temperature regulating mechanism (Samson et al., 2011). In this range the animal's heat exchange can be regulated solely by physical means such as constriction and dilation of blood vessels in the skin, ruffling up the fur or feathers and regulation of the evaporation from lungs and skin. For a typical tropical breed of cattle, the ‘comfort zone’ range from 100 C to 270 C while a tropical temperate cattle has between -10 C and 160 C (FAO, 1986). If there is a change in ambient temperature beyond either the upper or lower limit, physical regulation will not be sufficient to maintain a constant body temperature and the animal must, in addition, decrease or increase its metabolic heat production. The body mechanism for regulating animal body temperature is triggered to action to enable the body remains or return to normal (Samson et al., 2011). However, a further decrease or increase in temperature will eventually bring the temperature to a point beyond which not even a change in heat production will be sufficient to maintain homeothermy, hence, thermo-regulating mechanism may begin to fail, resulting in one or more of the following as elucidated by Samson et al., 2011: i.Abrupt rise in rectal temperature.
ii. Decline feed intake i.e. loss of appetite.
iii. Increase in water intake.
iv. Decrease in productive process such as growth and milk/egg production v. Loss in body weight i.e. emaciation.
vi.Change in composition of milk produced.
This partly explains the deterioration of highly productive cattle imported from temperate area to the tropics. However, very young animal, lacking fully developed temperature-regulating mechanisms, particularly the ability to increase heat production by increased metabolism, is much more sensitive to its thermal environment and requires higher temperatures. Other behavioural and physiological responses of animal to excessive high temperature or heat load include: i.Sweating