Feed & Additive Magazine Issue 17 June 2022

ISSUE FOCUS FEED & ADDITIVE MAGAZINE June 2022 43 In adequately ventilated rooms, birds can also lower their body temperature through convection, i.e. heat dissipation; this is caused by air movement and temperature difference between air pumped into the building and the air surrounding the birds. The most important factor is air velocity in the building, which depends on the birds’ external temperature and body mass. The value of that parameter on hot days should be around 2-2.5 m/s for birds kept on litter, and 2 m/s for those in cages. These metrics should provide air exchange levels, on hot days, at 8 m3/h. This calculation is for one kg of live weight and should enable complete air exchange in the building during heatwaves within a minute. Under optimal humidity conditions (40-70%), birds can cool down their bodies through water evaporation from the surface of the mucosa and respiratory tract, which is visible as panting. If the air humidity is too high in the facility, it hinders heat dissipation by the body and creates favourable conditions for growing pathogens dangerous to their health. Panting eliminates on average 540 calories per gram of evaporated water, which should be considered when calculating feed energy demands for hot days. During panting, an excessive loss of carbon dioxide occurs via the lungs, leading to alkalosis – an increase in blood pH value. The frequently used misting or evaporation panels, with constant relative humidity monitoring, enable air cooling without causing excessive damping of the litter. In absolutely no case should the litter, walls or birds be hosed down with water. Heat loss also occurs through conduction, which is when a body comes in contact with cold air, moist and cold litter or a cold water supply system, or while drinking water of a lower temperature than the body or by inhaling cooler air. LIFE-THREATENING HYPERTHERMIA IN BIRDS The above-mentioned mechanisms are often insufficient and result in the overheating of birds. During hyperthermia, a significant acceleration of metabolism occurs with a simultaneous loss of water. This leads to dehydration and disorders of

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