CLIMATE AND ANIMALS
DIFFERENTclimatic conditions favour ag ricultural activities, especially in crop production. Now, what about our livestock. Let us look at the general effects of climate and how they affect the animals’ physiology and how they can add to the general bur den of stress.
Farmers always would like to have good production from their livestock for example cows in milk. Cows which are high yielders, this involves an intense activity of body functions. Food intake, rumen fermentation, di gestion, absorption, liver func tion, chemical synthesis, transportation of nutrients are all increased.
This increased metabolic ac tivity in turn tends to increase the heart rate and oxidation pro cesses. To produce intensively the animal produces a lot of excess heat; like a petrol engine running at high speed.
Thus the ability to lose heat becomes a limiting factor in our situation and the tropics as a whole. This is important espe cially when imported animals are brought in from the temper ate regions into Zambia.
Even though they are im ported into this country they are bred for their good performance under cool or temperate conditions.
High humidity as we experi ence this at certain times of the year further decreases the abil ity of the animal to loose heat. Sweating is less effective because air that is already saturated is not able to receive any more water vapour by evaporation.
Likewise, heat loss via respira tory evaporation is lowered. In the humid situation it is almost impossible to keep high yielding dairy cows.
Adaptation to tropical climate like ours cannot be fully under stood. It may be the ceiling for high yielders is lower in our trop ical situation even if complete adaptations could be achieved by breeding.
Farmers can expect adapta tion to assist in heat loss through the following adaptations:
1. Adaptation by an individual animal over a year or so.
2. Adaptation by breeding new anatomical or physical features.
3. Increased number of sweat glands.
4. Increased capillary network in the skin
5. Large loose fold of skin as we see in our local breeds of cattle such as the Agoni and the Barotse breeds.
6. Smaller size so that the skin surface area/body weight ratio is raised.
Under the Zambian sun a white surface reflects more ra diation than a black surface, so you might suppose white skins would be best for places with a lot of sun.
In fact, the skin needs black pigment to absorb the sun’s rays, carry the heat away and thus prevent burning. Further, animals in the tropics such as in Zambia with unpigmented skins are susceptible to photosensiti zation as well as sun burn.
The ideal coat for our situa tion and the tropics at large is probably: -
1. Skin with black pigment.
2. Hair that is white, grey or silvery (these they are least ab sorbent colors).
3. Hair that is thin (not thick or curly to insulate)
4. Hair that is sleek and shiny, lying flat, making a reflect ing surface
In case of continuous cold, in sulation is the problem, energy needed for maximum productiv ity or growth will be lost as heat.
Coming to rainfall, relative hu midity is usually experienced be cause of moist, heat is lost faster and if the animal gets wet evapo ration comes in all this has to do with increased humidity.
However, heavy rainfall pre disposes the animal to skin dis eases such as Senkobo and so this adds to general stress bur den. Wind will help in the evapo ration and will carry more heat and equally help bring tempera ture down.
In semi-desert areas such as the Western Province would of ten have very hot days with in tense sunshine, followed by very cold nights.
The cooling off does give some relief after the heat, but generally such changes greatly add to the stress burden. Strong winds and rain showers will also worsen the effects of cold and produce more stress.
Finally, adaptation, animals will adapt themselves (become used) to new climate, even if this involves a reduction of produc tivity. It is the newly introduced animal which suffers the greatest stress.
Therefore, farmers should understand the situation we are in concerning the current hot climate being experienced. In farming, farmers sometime have to gamble with nature.