Sudden increases in ambient temperature during summer months often catch poultry producers off their guard. It is sudden change in temperature which invariably causes the most physiological damage. Body temperature rises, and feed intakes fall and as a result, growth rate and Feed Conversion Rate suffer. The damage is less evident in very young stock, whilst in fully developed broilers, and particularly the large roaster type males, the damage can be very serious with mortality often doubling, or even trebling normal levels. During both chronic and acute heat stress the rate of panting increases, in an attempt to increase evaporative cooling. Panting leads to an excessive loss of CO2 and consequently an imbalance in the acid-base ratio occurs. This causes a change in blood pH, with a loss in bicarbonate ions, resulting in a reduction on shell thickness, bone mineralization and growth rate. A rise in temperature leads to an increase in water consumption. Whilst the increase can be beneficial as a cooling agent, it also has a down side. An increase in water consumption invariably increases faecal moisture levels. This is indicative of a decline in the intracellular potassium level. Potassium plays a major role in controlling urinary losses in heat stress birds.
Posted on: Wed, 24 Jul 2013 11:59:13 +0000
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