Page 70 - Agriculture_Form_Three

Agriculture for Secondary Schools

decreases the birth weight of lambs. When temperatures are below 7 °C at breeding
time, ewes show improved reproductive efficiency. Similarly, goats are affected by
temperature, humidity and rain. In hot climates, goats need shelter from intense
heat during the day. In humid areas, they need protection from prolonged heavy
rain. Excessive wetting from rain can cause pneumonia and an increase in parasitic
infestation in goats.

In poultry, the environmental temperature vary with age. Chicks should be started at
35 °C in the first week after being hatched. The temperature is reduced gradually to
24 °C by the fifth week. Broilers and young turkeys reared at ambient temperatures
below 18 °C are heavier than similar stock reared within the 18 - 35 °C range, but
their feed utilisation will be less. Laying poultry produce the greatest number of
eggs and the largest sized eggs at 13 - 24 °C. The best feed utilisation is achieved
from 21 - 24 °C. With increasing environmental temperature, there is a decrease in
feed intake and alterations in behaviour. Within the temperature range of 5 - 30 °C,
there is a reduction of about 1.6 % in feed intake for every 10 °C increase in ambient
temperature. Above 24 °C, there is a reduction in egg production and egg size. A
continued rise in temperature to 38 °C or more may prove lethal. High humidity
at high temperatures creates conditions that are more likely to be lethal because of
breakdown in body cooling through respiration.

Rabbits are affected most by sun and heat, wind, rain and draughts. Sunlight is
of benefit to breeding stock and the growing young, but it will also fade the coat
of coloured rabbits and discolour a white one. While rabbits enjoy the sun, they
must have a chance to get out of the direct rays. Because of their thick fur coats,
they tolerate cold better than extreme heat but they are susceptible to chilling from
draughts. Rabbits also need protection from rain and dampness.
As far as microbiological environment is concerned, disease remains a major
profit-limiting factor in livestock production. Sanitary control measures should be
incorporated in any housing design so that a good hygienic standard can easily be
maintained. Livestock which are well fed and watered and in good condition will
not easily be attacked by diseases. Good housing management can remove or reduce
the effects of adverse environmental factors such as climatic stress, which otherwise
would weaken the animal’s body natural defence. New born stock should always
receive colostrum, that is, first milk, which contains antibodies. It takes time for an
effective immune system to develop in an animal and therefore good hygiene is of
special importance in housing young animals. Pens, in particular those for giving
birth, should be constructed in easily cleaned and disinfected materials and should
not have corners and recesses where manure and dirt can accumulate.

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