ENVIRONMENTAL PHYSIOLOGY
AGRICULTURAL SCIENCE

ENVIRONMENTAL PHYSIOLOGY

Environmental physiology refers to the effects of the environment on the growth and performance of farm animals. Normal growth and performance are enhanced when climatic factors like temperature, rainfall, wind, relative humidity, sunlight, etc are moderate. Excess or lack of these factors definitely will have a negative impact on the growth and overall performance of farm animals.

 

EFFECTS OF CHANGES IN CLIMATE ON GROWTH

Changes in climate have some effects on the growth of farm animals. These effects include:

  1. Extremes of either hot or cold conditions is unfavourable and reduces the performance of farm animals.
  2. Wind aids the spread of diseases (air borne disease, e.g ., tuberculosis) which cause retarded growth or even death of farm animals.
  3. High rainfall leads to the multiplication of tsetse flies which transmit trypanosomiasis and such disease reduces the growth or even leads to the death of farm animals.
  4. High temperature leads to heat stress in farm animals, e.g .,cattle, poultry and pig.
  5. High relative humidity affects food intake of farm animals.
  6. High intensity of radiation affects food intake of farm animals.
  7. High humidity in poultry houses causes mouldiness of feed,thereby leading to low feed intake and retarded growth.
  8. Moderate wind velocity promotes good ventilation and this enhances the normal growth of farm animals. Extremes of wind have negative impacts on the growth of animals.
  9. Increase in temperature of blood flowing through the brain of birds initiates panting and this in turn leads to water loss through evaporation.
  10. At low temperatures, there is reduced feed efficiency as more nutrients are needed for body maintenance, leading to poor growth.

 

Effects of temperature on:

a) Brooding of chicks:

  1. Temperature of 35 – 39°C provide warmth for the chicks.
  2. Temperature range of 35 – 39°C leads to proper development.
  3. Moderate/ideal temperature makes them to spread evenly and feed well.
  4. High temperature makes chicks to pant and move away and sit with their mouth open.
  5. Low temperature leads to hurdling together which may lead to suffocation and death.
  6. High temperature leads to poor feather development.
  7. High temperature leads to pecking.
  8. There is greater susceptibility to diseases at both high and low temperature conditions.
  9. Both high and low temperatures lead to retarded growth.
  10. Both high and low temperatures lead to poor feed efficiency/utilization.

 

EFFECTS OF CHANGES IN CLIMATE ON REPRODUCTION

Changes in climate have some effects on reproduction of farm animals. These effects include:

  1. Heat stress (i.e ., high temperatures) causes abortion in farm animals.
  2. High relative humidity affects the productivity of farm animals.
  3. High intensity of radiation causes heat stress in farm animals, thus reducing their reproductive capabilities.
  4. High temperature leads to low rate of conception or fertilization in farm animals.
  5. At high temperature, frequency of mating and quality and quantity of semen in breeder birds decrease.
  6. At high temperature, fertility and hatchability in breeder birds decrease.
  7. High temperature decreases ovulation in animals.
  8. Light controls sexual maturity i.e. low light intensity is desirable during rearing of pullets to prevent early sexual maturity.
  9. High rainfall and high humidity cause the chilling of young ones soon after parturition.
  10. High temperature decreases or reduces sexual activities in farm animals.
  11. Egg production is drastically reduced at extremes of temperatures.
  12. High temperature can reduce spermatogenesis of male animals.

 

EFFECTS OF CHANGES IN CLIMATE ON MILK PRODUCTION

Changes in climate have some effects on milk production by farm animals. These effects include:

  1. High relative humidity favours the growth of disease pathogens that can reduce milk production in farm animals.
  2. High intensity of radiation from the sun causes heat stress in animals, thus reducing their milk production.
  3. High temperature causes heat stress, thus reducing the rate of milk production in farm animals.
  4. High temperature and rainfall do not favour the rearing of dairy animals.
  5. High rainfall leads to the multiplication of tsetse flies which transmit trypanosomiasis in diary cows, thereby leading to low milk production.
  6. Extremes of rainfall do not favour the growth of grasses, leading to low feed, intake and less milk production by farm animals.
  7. Milk spoilage occurs at a temperature of 37°C.
  8. Pathogenic bacteria in milk are destroyed when milk is subjected to a high temperature of about 74°C (pasteurisation).
  9. Extremes of temperature affect feed intake, leading to low milk production.
  10. Physiological process are retarded at extremes of temperature leading to low milk production.

 

EFFECTS OF CHANGES IN CLIMATE ON EGG PRODUCTION

Changes in climate have some effects on egg production in poultry birds. The effects include:

a) Temperature

  1. High temperature causes a reduction in feed intake, leading to low egg production.
  2. It reduces spermatogenesis and libido in males.
  3. High temperature causes heat stress, thus reducing egg production.
  4. It may result in death of birds, particularly chicks and layers.
  5. It increases water intake in hot weather and reduces water intake in cold weather.
  6. It is necessary for incubation of eggs.
  7. High temperature leads to decrease in feed efficiency, leading to a low egg production.
  8. Egg storage period is reduced under high temperature.
  9. High temperature reduces hatchability of eggs.
  10. At high temperature, fertility and hatchability in breeder birds decrease.
  11. Extreme temperature leads to decrease in egg quality.
  12. Ideal or moderate temperature leads to better egg production.

 

Control of Heat/Temperatures

  1. Fans or air conditioners should be introduced.
  2. Enough windows or opening for ventilation should be provided.
  3. Windows should be covered with cloth materials to conserve heat.
  4. Vents should be provided at the roof tops.
  5. Poor conductors of heat should be used as roofing sheet. Sun-reflecting sheets can also be used or the roof should be painted with white. Pens should also have ceiling boards under the roof.
  6. Room heaters or lanterns should be used to warm buildings when it is cold.
  7. During construction, keep open parts of buildings away from direct solar radiation (i.e East-west direction).

 

b) Relative Humidity

  1. It is very important in incubation of eggs.
  2. High humidity compounds heat stress.
  3. Low humidity induces rapid water loss from the birds’ body and thus increases their water intake.
  4. High humidity encourages the spread of diseases .
  5. High humidity causes feed to go mouldy.

 

Control of Humidity

  1. This can be controlled by fixing of humidifyers or open trays filled with water to increase humidity.
  2. Free ventilation should be allowed when the humidity is high.
  3. Spilling of water in poultry houses should be avoided to reduce humidity or dampness.

 

c) Light

  1. It controls egg laying in hens.
  2. Duration of lighting controls time spent at feeding which regulates growth and the rate of feathering.
  3. Direct light of high intensity causes stress to the eyes.
  4. Bright light makes the birds active.
  5. Light makes objects visible.

 

Control of light

  1. In short day length, extra illumination should be provided.
  2. A reasonable part of the walls should be made up of wire mesh or glass to promote lighting.
  3. Windows should be covered with dark cloth to reduce light intensity.
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