Abstract
Semen processing and manipulation generally result in loss of sperm motility and sperm velocity due in part to oxidative stress. In this study we investigated the vulnerability of South African indigenous unimproved buck semen to oxidative stress induced by an oxidative stress inducing agent, namely, hydrogen peroxide (H2O2). Semen ejaculates were collected from four superior South African indigenous unimproved bucks in a total of ten collections and then each duplicate was treated with different concentrations of H2O2 in presence or absence of Dithiothreitol (DTT). Sperm motility and velocities were determined using the computer aided sperm class analyser (CASA). SYBR-14 and propidium iodide (PI) Live/Dead assay kit was used to determine cell viability and Yo-Pro-1 plus PI Apoptosis kit was used to determine apoptosis. Statistical analysis was performed on the data using SPSS version 17.0 for Windows (SPSS Inc., Chicago, IL). South African indigenous unimproved buck raw semen motility was between 97% with 98% viability and 0% apoptotic cells. Comparisons of the untreated controls at 0 and 3 hrs incubations revealed that after 3 hrs there was overall a decrease in the number viable cells with the majority of remaining cells exhibiting circular movements accompanied by high progressive (PM) and rapid (RAP) motilities. In treated South African indigenous unimproved buck semen, H2O2 marginally increased total motility (TM) with few apoptotic sperm cells while retaining high viability. Also, H2O2 increased straight line distances travelled of more than 4 fold as compared to untreated controls with no circularly moving cells. Moreover, inclusion of DTT, an antioxidant, had minimal effects on TM, RAP, curvilinear velocity (VCL), straight line velocity (VSL), linearity (LIN) and wobble (WOB) but positively affected PM, average path velocities (VAP), apoptosis and viability. Our Pearson’s correlation data revealed that only straightness (STR) was highly positively affected by H2O2. Overall, the South African indigenous unimproved buck semen resisted deterioration in TM, RAP, VCL, VAP, VSL, LIN, WOB, viability and apoptosis under oxidative stress conditions. These data suggest that the South African indigenous unimproved buck semen does not easily succumb to oxidative stress.
Highlights
There is growing interest in the cryopreservation of the buck semen worldwide [1] [2]
In this study we investigated the vulnerability of South African indigenous unimproved buck semen to oxidative stress induced by an oxidative stress inducing agent, namely, hydrogen peroxide (H2O2)
The raw semen obtained from the South African indigenous unimproved bucks showed an average sperm concentration of 0.876 ± 321.55 × 109 cells/ml, with a pH of 7.5 ± 0.5, viability of 98 ± 1.5 and no apoptotic spermatozoa (Table 2)
Summary
There is growing interest in the cryopreservation of the buck semen worldwide [1] [2]. Published data indicates that raw semen from this breed has TM above 83%, high PM, and high RAP accompanied by high viability [5]. Accompanying these features were high VAP, LIN, STR and WOB, characteristic of superior quality semen [5]. These experiments have revealed that following cryopreservation, the South African indigenous unimproved buck semen showed decreased TM to less than 40% with low PM and RAP, accompanied by lower VAP, LIN, STR and WOB, indicating deterioration of semen quality [5]
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