Mortality of Broiler Chickens During Summer Fattening Periods Affected by Microclimatic Conditions

Mortality of chickens during two summer fattening periods L1 and L2 in commonly used halls for chicken fattening in Slovakia have been evaluated in this paper. Effect of microclimatic conditions in housing area on recorded mortality has been analysed. Mortality was assessed in six halls, microclimate parameters and surface temperatures were continually measured only in one of the middle halls. It was documented that high mortality occurred during summer in the last phase (P3) of fattening period due to sudden hot weather waves. Daily mortality rate varied up to 447 birds in evaluated hall 3. During the last third of both fattening periods, it was significantly higher than during the first two phases (P_L1 = 0.0036; P_L2 = 1.4·10⁻⁶). Differences among halls were insignificant (P_L1 = 0.614; P_L2 = 0.413). In L1, average daily temperatures went beyond the recommended temperatures from 21^st to 31^st day. During L2, it was from 29^th to 31^st day and from 36^th to 38^th. The extra high mortality occurred in L1 on 31^st day (447 birds) and during L2 on 36^th day (88 birds), 37^th day (96 birds) and 38^th day (155 birds). High differential temperatures have been recorded and uninterrupted time periods (6 hours or more) with temperature higher than 30 °C and/or the relative humidity (RH) exceeding 70% were occurred during these days. In order to eliminate effect of sudden hot weather waves, modern digitally controlled microclimate regulation technologies (heat pumps, floor cooling, etc.) can be used, supported by data obtained from detailed microclimate analysis documented in this paper.