There are certain climatic factors that affects animal production, Therefore we are going to discuss about those direct effects of climate change on animal production and ways to handle them below
The Tropical Environment and its Moderating Factors
The tropical region lies between the latitudes (tropics) of Cancer and Capricorn in the north and south of the Equator.
By its geographical location, the region is expected to be uniformly hot all year round, but this is not so, A number of environmental factors moderate the hotness of the region such that several micro-climates (mini pockets of climatic condition) are created in certain places by factors such as distance away from the equator (the decree of latitude), altitude (height above sea level), soils and contours vegetation, ocean currents, wind, rainfall and distribution of land and water.
Differences between one micro-climates and another are noticeable by variation in such climatic elements as temperature, rainfall and to a lesser extent, humidity are the climatic elements of greatest influences in moderating conditions in a micro- climate.
Similarly, they also cause major effects on animal physiology, behavior and productivity through their individual or separate effects but, more often, by their combination with other environmental factors.
The influence of climate on animal production (including animal body functions, behavior and productive abilities) may be direct or indirect. In either way, system 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.
Direct Effects of Climate on Animal Production
It must be noted from the unset that responses of individual animal to certain climatic condition vary between individual animals of the same breed.
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 regulating mechanism. For a typical tropical breed of cattle, the ‘comfort zone’ range from 10 to 27 while a tropical temperate cattle has between -1 and 16.
If there is a change in ambient temperature beyond either the upper or lower limit, the body mechanism for regulating animal body temperature is triggered to action to enable the body remain or return to normal.
However, thermo regulative mechanism may begin to fail, resulting in abrupt rise in rectal in temperature, decline feed intake, an increase in water intake, a decrease in productive process such as growth and milk/egg production and perhaps a loss in body weight.
Sometime the composition of milk produces may be affected. This partly explains the deterioration of highly productive cattle imported from temperate area to the tropics.
Other behavioral and physiological responses of animal to excessive high temperature or heat load include sweating, panting, wallowing in mud or pool of water, reduction in physical exercise and mating activities.
Let us examine a few of these effects of temperature on animal conducts.
Effect of Climate Temperature on Grazing Activity
(a) The Effect of High Air Temperature on Cattle is Reflecting in their Grazing Behavior: Studies have shown that length of day time grazing is related to the ambient temperature, and reduction in heat load improves grazing behavior.
Herders in semi- arid and arid area have adopted the act of grazing at night to improve both intake and length of grazing in hot seasons to enable them adapt to their climatic considerations.
Fast growing broiler birds are often fed in the night and sprinkled with droplets of water in the day as means of alleviating heat load to improve feed intake and overall production.
(b) Effect of Temperature on Growth and other productive Performance:
High ambient temperature depress appetite and reduce feed intake and grazing time which may also diminish production as measured by growth, milk yield and milk solids production.
Experimental evidence has shown that there is a partial correlation with growth rate when body weight is constant. However, under good management conditions where feeding and management are adequate, high ambient temperatures do not appreciably affect growth rates.
Temperate type sheep in the tropics of Australia that are exposed to high air temperature often have a low lambing percentage and give birth to small weak lambs that have a high post-natal mortality.
Lambs born in early summer and reared through hot summer are usually smaller at birth than lambs born in the cool months of early dry season. In poultry light breeds and young chicks are more resistant to heat than heavy breeds and adult birds.
High temperatures predispose laying birds to abrupt decline in egg production.
(c) Effect of Temperature on Milk Yield and Composition: Studies have indicated the effect of temperature on milk yield, butter fat and solids – not – fat. All these are depressed by high temperature, but usually by indirect effect of temperature on changes in feeding.
As much as between 44 per cent and 55 percent differences in milk yield and butter fat production were noticed between twin heifer reared under sound tropical and temperature management conditions with increasing air temperatures appetite is depressed food intake lowered, and heat production reduced.
The exact mechanism of temperature effect on milk and milk composition is not known. Either the high temperature directly affects appetite, thus decreasing feed intake productivity and heat production or the need to reduce heat production forces down appetite and hence lower feed intake.
The direct effect of temperature is further appreciated in a study that define optimum temperature(°C) for milk production 21-27 in Jersey and Holstein 29-32 in Brown Swiss and higher in tropical breeds of cattle.
Similarly, milk constituents namely; butter fat, chloride, lactose and total nitrogen are affected when temperature rises above 27-30.
(d) Effect of Temperature on Reproduction: Air temperatures do not seem to affect reproduction cycle of cows, but bull fertility is markedly influenced. High testicular temperatures adversely affect spermatogenesis and hormonal system.
Seminal degeneration and temporary infertility have been 33°C over a length of time. Both sizes of egg and thickness of its shell decline when laying fowls are exposed to high temperatures.
Egg productivity decline has been experienced in poultry farms in Nigeria. However incubation and brooding are favored under high temperature.
As stated earlier, it is difficult to separate or single out the effect of temperature, precipitation and humidity on animal production. Evaporation is one of the important channels of heat loss.
It depend on ambient air temperature, the amount of available moisture in the atmosphere (humidity), area of evaporating surface and the degree of air movement.
The amount of available moisture partly affects the rate of evaporative heat loss from the skin and respiratory system of an animal.
High humidity adds to the heat load of the animal by depressing evaporative heat loss with declining effect on feed intake and productivity as demonstrated under temperature effects.
(3) Solar Radiation
The quantity of solar radiation received in tropical region differs profoundly from the temperate. For tropical breeds of animal, solar radiation effects are scarcely noticeable because of their skin and eye that are pigmented.
When temperate breeds are exposed suddenly to solar radiation of the tropics they suffer from sun burns or skin cancers, epithelioma (eye infection from solar radiation) and other photosensitive disorders.
Solar radiation correlate with air temperature and thus partly contributes to the ambient temperature which is a principal climatic element affecting animal production.
Climate Management system adopted in the tropics are a means for minimizing adverse effects of solar radiation such as grazing in the night, clipping of excessive hair, grazing under shades in the day time etc.
Solar radiation may contribute or may even create a more severe heat stress.