ABSTRACT

The impact of acute heat stress on growth performance and blood chemistry in four strains of broiler chickens were assessed. A total of eight hundred, 28 d old broiler chickens of four strains [Ross (RS), Arbor Acre (AA), Hubbard (HB) and Marshall (MS)] were randomly assigned to either; no heat stress (No-HS) or 30 min of acute heat stress, (30MAHS) at 40±1^oC for 3 consecutive days at 28-30, 35-37, 42-44, and 49-51days of age, during which their performance data were recorded. On the 23^rd day of the experiment, 20 birds per strain were randomly selected in each treatment group for haematology and serum chemistry determination. Data were subjected to a 2 x 4 factorial arrangement in a completely randomized design model. The 30MAHS birds had lower (p<0.05) final body weights, weight gain, feed intake and feed conversion ratio, and higher (p<0.05) mortality than the No-HS birds. The concentrations of leucocytes, lymphocytes, granulocytes, haemoglobin, mean corpuscular volume, packed cell volume, and plateletcrit were higher (p<0.05) in the No-HS birds than in the 30MAHS birds. Serum protein, albumin, total cholesterol, and glucose were lower (p<0.05) in the 30MAHS than in the No-HS birds. Broiler strains affected (p<0.05) growth performance and some blood parameters in the chickens. There were significant interactions (p<0.05) between acute heat stress and broiler strain on the growth performance indices, and some blood parameters. Regardless of heat stress condition, RS had higher (p<0.05) body weight gain, and feed efficiency than the other strains. Nonetheless, the 30MAHS Ross had the highest (p<0.05) mortality while 30MAHS AA had the lowest (p<0.05) mortality. These results evinced that broiler strains respond differently to acute heat stress.