Dietary flaxseed oil and sunflower oil supplementations support heterophil functions, T cells, and antioxidant defence system in laying hens exposed to stocking density stress

Abstract

This study aims to investigate the impact of stocking density stress on heterophil functions, T cells, inflammatory cytokine levels, and antioxidant defence mechanisms. In addition, we aimed to investigate the potential protective effects of flaxseed and sunflower oil supplementations against stocking density stress in laying hens. One hundred and forty-four hens were divided into two groups: stressed and non-stressed hens, which in turn were divided into three subgroups: basic feed, linseed oil and sunflower oil groups. Stocking density stress was induced by a space allowance of 357 cm per hen. Birds in the basal diet group were fed on commercial laying hens' feed, while supplementation groups received 2% of flaxseed or sunflower oils. The heterophil/lymphocyte ratio (H/L) (P = 0.018) and the serum TNF-alpha and malondialdehyde (MDA) levels (P = 0.028) were increased whereas chemotaxic (P = 0.006) and phagocytic activities (P = 0.001) and the serum ascorbic acid level (P = 0.057) were reduced in the stressed hens. Chemotaxic activity (P = 0.014) and oxidative burst (P = 0.001) of the heterophils were increased in the sunflower diet-supplemented hens. Serum TNF-alpha (P = 0.028) and interleukin-1 beta (IL-1 beta) (P = 0.012) levels were reduced by sunflower diet supplementation in the stressed and unstressed groups, respectively. Flaxseed diet supplementation increased the CD4/CD8 ratio (P = 0.031) while decreasing MDA level (P = 0.028) in stressed hens. Glutathione peroxidase (GSH-Px) level was increased (P = 0.007) in the unstressed hens by flaxseed diet supplementation. Flaxseed and sunflower oils positively affected specific and non-specific immune responses, pro-inflammatory cytokine levels, and the antioxidant defence system and alleviated some adverse effects of stress response in laying hens. It was concluded that dietary flaxseed and sunflower oil supplementations were beneficial for stress-exposed hens.