Effects of low ambient temperatures and dietary vitamin C supplement on growth performance, blood parameters, and antioxidant capacity of 21-day-old broilers

The study was conducted to determine the effects of low ambient temperature (LAT) and a vitamin C (VC) dietary supplement on the growth performance, blood parameters, and antioxidant capacity of 21-d-old broilers. A total of 400 one-day-old male Cobb broilers were assigned to 1 of 4 treatments as follows: 1) LAT and a basal diet; 2) LAT and a basal diet supplemented with 1,000 mg of VC/ kg (LAT + VC); 3) normal ambient temperature (NAT) and a basal diet; 4) NAT and a basal diet supplemented with 1,000 mg of VC/ kg (NAT + VC). All birds were fed to 21 d of age. Broilers in groups 1 and 2 were raised at 24 to 26 degrees C during 1 to 7 d, and at 9 to 11 degrees C during 8 to 21 d, whereas groups 3 and 4 were raised at 29 to 31 degrees C during 1 to 7 d and at 24 to 26 degrees C during 8 to 21 d. The LAT increased the feed conversion ratio during the whole experimental period (P < 0.01), whereas it increased heart index at 21 d (P < 0.05) and hematocrit and hemoglobin level at 14 d (P < 0.05). Supplementing the diet with VC increased hematocrit, hemoglobin, and red blood cell count at 21 d (P < 0.05). At 21 d, LAT conditions decreased total antioxidant capacity in the serum, liver, and lungs (P < 0.05), and it also increased the levels of VC in the serum and liver, the amount of protein carbonylation in liver and lungs, and the malondialdehyde level in the lungs (P < 0.05). The addition of VC tended to increase the total antioxidant capacity level in serum (P < 0.1). Low ambient temperature resulted in oxidative stress for broilers that were fed from 1 to 21 d of age, whereas no significant effect was found on the antioxidant activity by dietary VC supplementation.