EffEct of ElEvatEd air tEmpEraturE on somE quality paramEtErs of broilEr chickEn mEat* * Iwona Skomorucha, Renata Muchacka, Ewa Sosnówka-Czajka Department of Technology, Ecology and Economics of Animal Production, National Research Institute of Animal Production, 32-083 Balice n. Kraków, Poland abstract the aim of the study was to determine the effect of elevated air temperature in the first period of rearing broiler chickens from two commercial lines on selected quality parameters of their meat. day-old ross 308 and hubbard flex broiler chickens were assigned to 4 groups. Groups i (ross 308) and ii (hubbard flex) were kept under standard thermal conditions throughout rearing, and groups iii (ross 308) and iv (hubbard flex) were exposed to 10°c higher than recommend- ed air temperature from 1 to 21 days of rearing. simplified carcass analysis was performed at 42 days of the experiment. meat ph was measured 15 min postmortem and 24 h after carcass chill- ing. carcass colour and water holding capacity of meat were also determined. it was concluded from the results obtained that heat stress applied in the study decreased the ph of breast muscles, measured 15 min postmortem in broiler chickens from both commercial lines, which was probably associated with a tendency for lower water holding capacity of meat. it can thus be presumed that elevated air temperature in the first period of growth may negatively affect the quality of meat. Elevated air temperature did not have an adverse effect on the dissection results of broilers. the origin of birds influenced most dissection parameters, ph 15 of breast muscles and broiler carcass colour. the dissection results indicate, however, that the body’s reaction to heat stress may vary according to the origin of chickens. key words: broiler chickens, commercial line, meat quality, heat stress High air temperature in broiler houses is recognized as one of the main factors negatively influencing avian productivity (Lu et al., 2007) and meat quality (Akşit et al., 2006; Wang et al., 2009). McKee and Sams (1997) report that heat-stressed birds are prone to disturbances in muscle energy metabolism, with poultry breast muscles that are the site of glycolytic metabolism being particularly susceptible (Sandercock et al., 2001). These authors report that heat stress leads to acid-base changes in blood, affects postmortem glycogen levels in muscle and decreases pH of  This study was conducted as part of statutory activity, project No. 4136.1. Ann. Anim. Sci., Vol. 10, No. 2 (2010) 187–196