Effect of different periods of chronic heat stress with or without vitamin C supplementation on bone and selected serum parameters of broiler chickens

This study evaluates the effect of different periods of chronic heat stress (CHS) on selected bone and serum parameters of broiler chickens with or without vitamin C administration. Ninety 23-day-old chickens were randomly allocated into seven groups: (1) control, (2) short-term CHS (5 days), (3) short-term CHS+vitamin C (12g/100l drinking water of a 50% product), (4) medium-term CHS (10 days), (5) medium-term CHS+vitamin C, (6) long-term CHS (20 days) and (7) long-term CHS+vitamin C. In heat-stressed groups the temperature was increased to 39 +/- 1 degrees C for 8h/day. At the end of the experiment, blood samples were collected and shank, keel and tibia bones were removed. CHS was not associated with a drastic change in serum Ca and corticosterone, or bone characteristics (both cortical and trabecular bones in radiographical and histological evaluation), or birds' performance. Oxidative stress was present especially with short-term CHS. CHS, especially for short or medium periods, showed a tendency to increase serum vitamin C and administration of this vitamin did not make a significant change in its serum levels although it ameliorated oxidative stress. In conclusion, it seems that CHS is not associated with an appreciable change in broiler performance, bone characteristics, or selected serum parameters; and simultaneous vitamin C administration at the dosage of 12g/100l in drinking water has no beneficial effect apart from reducing oxidative stress especially in short-term chronically heat-stressed birds.