The Effect of Oxidative Stress and Dietary Vitamin E Supplementation on Fresh Sperm Quality of Ross 308 Broiler Breeder Roosters

Introduction : 

 Oxidative stress is an imbalance between oxidants and antioxidants at the cellular level which leads to the condition of infertility in male. Oxidation of cell macromolecules, cell death by necrosis, apoptosis and damage of tissue structure are the results of another oxidative stress damage. This process eventually leads to a variety of diseases, reduced growth performance and even death (Min et al. 2018). Poultry face a variety of environmental, technological, nutritional, and biological stresses that reduce their productivity and reproductive performance. Most of these stresses at the molecular level are associated with oxidative stress and damage to biologically important molecules (Surai et al. 2019). Qualitative characteristics of sperm, blood testosterone level, and plasma lipid peroxidation are affected by severe oxidative stress (Khan, 2011). Vitamin E is an important known antioxidant and protect cell membrane of sperm cell from damage of reactive oxygen species in male reproductive system of animal. Feeding of this vitamin has beneficial effect on testes weight, semen quality indexes, testosterone and antioxidant enzymes such as glutathione peroxidase and superoxide dismutase in birds and mammals. The objective of this experiment was to investigate the effect of diet vitamin E supplementation on fresh sperm quality in broiler breeder roosters challenged with oxidative-stress.

Eighteen Ross 308 male broiler breeder at 28 weeks of age were randomly assigned into 3 experimental groups including control group, dexamethasone group (subcutaneous injection of 4 mg dexamethasone per kg body weight) and dexamethasone group receiving supplemented diet with of vitamin E (200 mg per kg of feed). Each experimental group consisted of 6 birds. Sperm samples were taken from roosters using abdominal massage method and analyzed for quality characteristics and antioxidant status. Sperm concentration was determined by counting spermatpzoa using hemocytometer. The pooled sperm sample was diluted by using poultry semen extender and then 10 µl of diluted sperm mixed with 10 ml of 3% NaCl. The chambers of hemacytometer filled with 10 µl sperm suspension and allowed to settle for 3 mines.  Numbers of sperm cell in 5 of the large squares of chamber were assessed. Computer assisted semen analyses (CASA) were performed to determine sperm motility, with settings adjusted to detecting domestic fowl according to a previously described method (Froman and Feltmann, 2000). Total, progressive and non-progressive motility (%), as well as immotile sperms were measured. Also, sperm kinematic values including straight line velocity (VSL (µm/s)), curvilinear velocity (VCL (µm/s), average path velocity (VAP (µm/s), amplitude of lateral head displacement (ALH (µm), and beat-cross frequency (BCF (Hz) were measured. Progression ratios were also calculated using the mentioned velocity measurements: straightness (STR = VSL/VAP) and linearity (LIN = VSL/VCL).

The results indicate that dexamethasone-induced oxidant stress caused an increase in MDA levels (5.4) and a decrease in the activity of antioxidant enzymes such as glutathione peroxidase (52.51) and superoxide dismutase (108.62), as well as sperm motility parameters and sperm cell membrane integrity in comparison to the control group. However, when vitamin E was added to the roosters' diet, it improved the negative effects of oxidative stress on sperm motility parameters, antioxidant status (Total antioxidant capacity (1.65), superoxide dismutase (155.10) and glutathione peroxidase (87.77) enzymes), sperm viability (88.05), and sperm cell membrane integrity (89.72) (P<0.05). These findings suggest that dexamethasone injection caused a sharp decline in sperm quality by reducing sperm motility, antioxidant enzyme activity, and plasma membrane integrity, while vitamin E supplementation improved sperm quality by enhancing the antioxidant status and protecting the sperm cell membrane from the damage caused by reactive oxygen species in broiler breeders. Avian sperm are highly susceptible to lipid peroxidation due to their high content of long-chain polyunsaturated fatty acids. Lipid peroxidation produces reactive species that damage sperm membrane function and motility, ultimately reducing the fertility potential of aged roosters. Therefore, the antioxidant defense plays a critical role in maintaining semen quality (Surai et al., 2006).

It can be concluded that the inclusion of vitamin E in diet remarkably improved the sperm motility characteristics and antioxidant status of sperm in broiler breeder roosters challenged with oxidative stress. On bases of this finding it’s recommended to use of vitamin E in the rooster diet to elucidate negative effect of oxidative stress.