Role of ascorbic acid in chicks exposed to high environmental temperature.

This study was conducted to determine if ascorbic acid (AA) 1) increases resistance to high environmental temperature in young chickens and 2) alters heat-induced changes in several physiological responses. Groups of male chicks received either a standard ration containing 1,000 mg/kg (ppm) of AA or the ration without AA. Chicks were brooded for 3 wk and then maintained at 22 +/- 0.8 degrees C. At 4 wk of age, both AA-supplemented and control chicks were exposed to 30 min of heating (43 +/- 0.1 degrees C and 40 +/- 2% rh) on each of 3 consecutive h in an environmentally controlled chamber. Chicks were challenged with sheep erythrocytes (1 ml, 10(5) cells, iv) 12 h postheating. Heating reduced plasma potassium, body weight gain, relative bursa and spleen weights, and anti-sheep erythrocyte levels. Heating increased cloacal temperature, plasma protein, corticosteroid levels, and mortality. AA ameliorated many of these stress-related responses.