Biological and nutritional stressors can compromise the welfare of birds. These are due to changes in the normal levels of biochemical and physiological parameters of the birds which can be measured at different loci to determine the severity of the stresses. This study evaluated the haematological and biochemical traits as stress indicators in three genetic strains of broilers (Arbor Acre, Cobb-500, Marshall) reared at two stocking densities (16 birds per m2 and 18 birds per m2) for 28 days. A total of four hundred and thirty-two 4-week old birds were used in a completely randomized design of 3 × 2 factorial with three replicates of 24 birds each. The blood samples of selected birds collected at 56 days of age were evaluated for hematological and biochemical parameters using standard laboratory procedures. At the haemoglobin, total protein, albumin, triglyceride and cholesterol loci, there were no indications that the three strains were stressed. The MCH, MCHC, WBCs, eosinophils, heterophil/lymphocyte ratio and the corticosterone levels suggested that the birds were under stress at both densities. Most of the haematological and biochemical traits investigated in this study are indicators of stress bio-makers.

Keywords: Arbor Acre, Cobb-500, haematology, biochemical traits, Marshall, stocking density