Effect of stocking density on productive performance, behaviour, and histopathology of the lymphoid organs in broiler chickens

Abstract

Abstract Stocking density is one of the most important aspects of management in poultry production and considered a major concern in terms of the welfare of birds. It can also be a factor predisposing to stress and disease in birds. The aim of this study was to assess the effect of three different levels of stocking density on the productive performance and behaviour of broilers, as well as pathologic changes in the lymphoid organs that reflect immune status. Cobb 500 broilers were allocated to three groups with different stocking density: 10 birds/m 2 (Group 1), 15 birds/m 2 (Group 2), and 20 birds/m 2 (Group 3). Body weight was recorded weekly and weight gain was calculated from the data obtained. The behavioural patterns of the birds were recorded. On day 23 of the experiment, three birds from each stocking density group were injected with 10% sheep red blood cells and killed 10 days later. The thymus, bursa of Fabricius, and spleen were removed for histopathologic examination. Higher stocking density negatively affected final body weight as well as cumulative body weight gain. The higher density was also associated with decreased crouching, walking, preening, body care behaviour, and ingestive behaviour. Birds in the high stocking density group showed severe diffuse and extensive necrosis of the bursal follicles as well as atrophy and depletion of the splenic lymphoid nodules. These lymphoid organ disorders suggest that high stocking density compromises the immune response in birds. The negative effect of high stocking density on final body weight would decrease profitability.