Improving of frozen-thawed sperm quality in commercial broiler breeder roosters challenged with dexamethasone using diet vitamin E supplementation

Oxidative stress is an imbalance between the free radicals and the ability of the body to counteract or detoxify their harmful effects by antioxidants. Commercial poultry faces a wide range of environmental, technological, nutritional, and biological stresses, which are responsible for low productivity and reproductive performance in poultry. In addition, chronic oxidative stress can deplete antioxidant vitamins and trace elements, impair immune function resulting in significant economic losses to the poultry industry. Most of this stresses at the molecular level are associated with oxidative stress and damage to important biological molecules. High levels of fatty acids are found in the plasma membrane of sperm cells. Fatty acids and other lipid compounds in sperm membranes play an important role in regulating spermatogenesis, sperm maturation, acrosome reaction, capacity building, and membrane fusion. Specifically, sperm lipid peroxidation disrupts these functions and inhibits spermatogenesis. Oxidation of sperm fatty acids leads to the production of free oxygen radicals (ROS), which are normally necessary for physiological processes of sperm, but excessive production of ROS in sperm causes low membrane fluidity, DNA breakdown (directly by attacking the purine and pyrimidine bases), protein damage, and ultimately reduced sperm motility and fertility. ROS cause damage via single and double strand DNA breaks, cross links, and chromosomal rearrangements) vitamin E is one of the most important natural antioxidants and effective in preventing of the spermatozoa lipids oxidation. Consumption of high amounts of vitamin E (200 mg / kg diet) increases its concentration in blood and semen plasma and causes beneficial changes in antioxidant capacity and lipid profile of rooster semen in normal conditions. Therefore, the aim of this study was to investigate the effect of diet supplementation with vitamin E on the quality of frozen-thawed sperm in breeder rooster under dexamethasone-induced oxidative stress.

A total of 18 roosters of Ross 308 broiler breeder at 28 weeks of age were completely randomized with 3 experimental groups and 6 birds in each experimental group. Experimental groups include 1- Normal rooster fed basal diet (control) 2- Roosters treated with subcutaneous injection of dexamethasone 4 mg / kg body weight (DEX) 3- Dex + Vitamin E (200 mg / kg diet). After 2 weeks of habitation period and 3 weeks after experimental treatments, semen samples of roosters were collected twice a week from each rooster using abdominal massage method. Sperm viability was assessed by eosin-negrosin staining. For this purpose, mix 10 μl of diluted semen with 20 μl of dye containing eosin dye (1.67 g), nigrosin dye (10 g) and sodium citrate (2.9 g) in 100 ml of distilled water. The viability of sperm was examined by light microscope (Olympus, Japan) with a magnification of 400 × and sperms that were completely or partially reddish and those did not stain were considered died and live sperm respectively. Qualitative characteristics of sperm including viability, percentage of total (MOT, %), and progressive motility (PROG, %), plasma membrane integrity as well as malondialdehyde content, antioxidant capacity (TAC) and activity of glutathione peroxidase (GPx), superoxide dismutase enzymes (SOD) were evaluated. Statistical analyses were performed using SAS software version 9.1. Duncan’s test was used to compare groups.

The results showed that dexamethasone injection as a cause of oxidative stress, increases lipid peroxidation (9.11) and decreases antioxidant capacity (1.01) of sperm (P<0.05). Total motility (49.16), progressive motility (12.46), survival rate (50.84) and plasma membrane integrity (50.26) significantly decreased by DEX treatment (P<0.05). Dietary supplementation with vitamin E improves total motility (73.63), survival rate (74.12) and plasma membrane integrity (72.74), antioxidant capacity (1.50) and activity of glutathione peroxidase (73.58), superoxide dismutase (144.95) and reduction of malondialdehyde (4.61) compared to the other two groups (P<0.05). Progressive motility (26.33) was highest in the control group compared to the other two groups and Lateral Head Displacement (16.08) was higher in the dexamethasone group than the other experimental groups (P<0.05). These positive effect vitamin E on sperm quality could be due to its antioxidant properties.

It can be concluded that dexamethasone injection increases lipid peroxidation and decreases sperm quality. Addition of vitamin E to the broiler breeder rooster’s diet under oxidative stress condition improves the quality of frozen thawed sperm. Therefore, it is recommended to supplement the diet of broiler breeder roosters with vitamin E under oxidative stress conditions.