Abstract
This study was done to investigate the effect of inclusion of ascorbic acid (AA) and Hibiscus sabdariffa in broiler chicken feed on haematological and oxidative stress parameters during the hot-dry season. Sixty day old chicks were used for the experiment, and were assigned to three dietary treatments with 20 birds per treatment and four replicate in a completely randomized design. Treatment 1 was the control with no supplements, treatment 11 was supplemented with AA at the rate of 500 mg/kg in feed and treatment 111 had Hibiscus sabdariffa at the rate of 2.5 % inclusion rate in feed. On the last day of the experiment half of the birds were randomly selected from each dietary group and blood sample (2 ml) was obtained through the wing web and divided into 2 parts; one for determination of haematological parameters while the second part was centrifuged and the resultant serum harvested and stored. The results indicated that the values of PCV, haemoglobin and total erythrocyte count obtained in T1 were all significantly (P < 0.05) lower than the recorded corresponding value in T2 and T3. The recorded values of malondialdehyde obtained in T1 was significantly (P < 0.05) higher than the values recorded in T2 and T3 while the values of superoxide dismutase, catalase and glutathione peroxidase were significantly (P < 0.05) higher than the obtained values in T2 and T3. The fragiligram was shifted more to the left in T3 than the other 2 treatments (P < 0.05).
In conclusion dietary supplementation of AA and Hibiscus sabdariffa calyces alleviated the adverse effects of heat stress in broiler chicken. It is thus recommended that Hibiscus sabdariffa calyces in the diets at the rate of 2.5 % could provide ameliorative effect against heat stress in broiler chicken during the hot-dry season.

Key words: Hibiscus sabdariffa, Broiler chicken, Haematology, Oxidative stress, Hot-dry season