Time dependent impact of reactive oxidants on seminal attributes of murrah bull during cryopreservation and storage

Cryopreservation is an invaluable technique yet it is also known to be detrimental to sperm function and fertility due to cryo-injury and concomitant generation of reactive oxidants. During laboratory manipulation for the cryopreservation and freeze-thaw process, spermatozoa undergo osmotic stress, ionic imbalance, metabolic decoupling, membrane phase transition, destabilization of the cytoskeleton and antioxidant depletion which communally hampers the semen quality.

With the aim of determining implications of cryopreservation and storage, semen samples were collected by artificial vagina technique from 12 Murrah bulls and subsequently examined at 0 hour (before cryopreservation) and at 24 hour, 1 month and 2 month of storage for various seminal attributes. Simultaneously seminal plasma was separated and preserved at -20°C till the analysis of biochemical indicators of semen quality viz., nitric oxide (NO), total antioxidant quantity (TAC) and lipid peroxidation status (TBARS).

A sharp reduction (p<0.01) in the semen quality was observed only at 24 h after cryopreservation except for viability. Significant reduction (p<0.05) in viable counts was observed up to 1 month interval. The capacitated sperm percentage was greater (p<0.01) in the cryopreserved semen as compared to fresh ejaculate. The mean±SE levels of NO (μmol/L), TAC and TBARS (Units/ml) was 2.31±0.27, 0.73±0.04 and 1.11±0.16 respectively in seminal plasma of neat semen stored at -20°C, while the values in the extended seminal plasma after cryopreservation was 2.37±0.31, 0.44±0.03 and 0.65±0.03 respectively. So it can be inferred that most of the damage encountered by spermatozoa is during the initial period of freezing, but the damage associated by various stressors cannot be ignored.