The effect of ascorbic acid (vitamin C) on freezability and spermatological characteristics of ram semen diluted by extenders containing different proportions of glycerol

ABSTRACT This study was conducted to investigate the effects of intramuscular » administration of ascorbic acid on spermatological characteristics in rams, and influence of semen diluted by extenders containing different proportions of glycerol and vitamin C on semen frezability and spermatological parameters. In this investigation, six Akkaraman rams were used. Semen was collected by electroejaculator once every three days during one month. Blood samples were taken after semen collections. After the intramuscular administration of vitamin C at a dose of 20 mg/kg/day during 30 days, blood and semen samples were taken similarly once in three days during injections. All ejaculates were evaluated for spermatological characteristics. Vitamin C levels were determined in blood serum and semen samples. In the second part of the experiment, semen collected from the same rams were pooled in a glass tube. Pooled semen were diluted in 1:4 (v/v, semen: extender). It was cooled slowly to 4°C within 2 h. Each of the resulting diluted and cooled 20 semen groups was diluted 1:1 with one extender group containing different proportions of glycerol (0,1,3,5,7%) and ascorbic acid (0,0.5,1,2 mg/ml). Extended semen was packaged in 0.25 ml French straws. The semen was allowed to equilibrate for 4 h before freezing. The straws were frozen in liquid nitrogen vapour. The straws from each treatment were thawed in a water bath at 38°C for 25 s. After administration of vitamin C, significant increases were observed in the average vitamin C levels in blood serum and semen of rams (PO.01), the average semen volume and sperm concentration (P<0.05), but the changes in the average sperm motility and other spermatological characteristics were not significant (P>0.05). There was no significant difference in spermatological characteristics depending on the increase in proportions of vitamin C after glycerolation, equilibration, freezing and thawing. After glycerolation and equilibration, though the increase in the glycerol levels reduced motility (P<0.05), it raised the rate of dead sperm, the rate of acrosomal damaged spermatozoa, and the total rate of abnormal spermatozoa (P<0.05). After freezing and thawing, while the increase in the level of glycerol raised motility, the rate of acrosomal damaged spermatozoa and total rate of abnormal spermatozoa (P<0. 05), it reduced the rate of dead sperm (PO.05).In conclusion, intramuscular administration of vitamin C in rams increased semen volume and spermatozoon concentration. Therefore, intramuscular administration of vitamin C in rams can improve semen quality in breeding season. Although the increase in glycerol levels (0%-7%) in diluted semen had negative effects on spermatological charecteristics after glycerolation and equilibration, the best results were observed in diluted semen groups containing 5% glycerol after freezing and thawing. However the increase in the proportions of vitamin C in extended semen did not change the spermatological characteristics. Keywords : Ram, Semen, Freezing, Vitamin C, Glycerol