Characterization and cryopreservation of South African unimproved indigenous goat semen
MetadataShow full item record
Semen from 7 South African unimproved indigenous bucks that were successfully trained from a group of 10 bucks for semen collection with the aid of an artificial vagina (AV) was characterized and then cryopreserved, using different semen extenders. Semen was collected twice a week and evaluated macroscopically for ejaculate volume and pH immediately after collection. Within 1h of collection, semen was further analysed electronically for sperm concentration. Thin semen smears were stained with eosin/nigrosin and evaluated under a fluorescent microscope for viability (percentage live or dead) and morphology (percentage normal or abnormal). In addition semen samples were evaluated using the computer assisted sperm analysis (CASA) for sperm motility (static, non progressive and progressive), velocities (static, slow, medium, rapid, VCL, VSL and VAP) and linearity (LIN, STR and WOB) parameters using a Sperm Class Analyser® (SCA®). Four different semen extenders, namely: Tris-1.5% yolk, Tris-15% BSA, Ovixcell® and Bioxcell® (IMV, L’Aigle, France) were used to cryopreserve pooled semen samples, with and without 6% glycerol thus making a total of 8 treatments. Immediately after dilution and after thawing, semen samples were compared through the evaluation of viability, morphology, motility, velocity and linearity parameters, using the same methodology used for fresh semen. Semen was then incubated at 37ºC and analysed for motility and velocity parameters after 30 and 60 minutes of incubation. Regarding the fresh semen samples, the South African unimproved indigenous bucks recorded an overall average ejaculate volume of 0.5 ± 0.2 ml, pH of 7.5 ± 0.2 and sperm concentration of 681.7 ± 74.6 x 106 sperm/ml. On average, bucks recorded 79.0 ± 6.3% normal and 76.3 ± 8.2% live sperm cells in the ejaculates. The average percentage of sperm abnormalities on head, mid-piece and tail were 4.2 ± 1.3%, 4.6 ± 1.7%, and 12.1 ± 5.4%, respectively. The overall sperm abnormalities recorded were 1.0 ± 0.8%, 9.5 ± 2.9% and 10.1 ± 3.6% for primary, secondary and tertiary abnormalities, respectively. The mean static, nonprogressively motile (NPM), progressively motile (PM), slow, medium and rapid sperm cells recorded were 30.9 ± 14.7%, 32.1 ± 10.9%, 37.3 ± 10.0%, 4.9 ± 1.7%, 6.0 ± 1.7% and 58.2 ± 14.1%, respectively. Viability of goat sperm following fresh semen dilution with the four different semen extenders was similar, however a reduction of approximately 20% in the percentage live and normal sperm was recorded (5-10 minutes after dilution), when compared to the fresh undiluted pooled semen sample. Similar motility parameters were recorded shortly after fresh semen dilution using the 4 different extenders. A slight decrease of approximately 4% in the extended semen’s sperm motility was observed, when compared to that of fresh undiluted semen. For the sperm velocity parameters, semen extended in Tris-BSA showed significantly higher medium sperm velocity. Following freezing-thawing, a drastic reduction in the percentage live and normal sperm was recorded in all treatments. Bioxcell® without glycerol recorded the highest number of live and normal sperm. The Bioxcell® and Ovixcell® extenders recorded the highest percentage linearity and straightness movement of the sperm. In general, cryopreservation reduced the sperm cell viability and motility parameters. In addition no effect of extender on the morphology of South African unimproved indigenous buck sperm was observed. Sperm motility and velocity results showed that sperm extended in Bioxcell® and Ovixcell® recorded higher values immediately post-thawing, while the Tris-based extenders recorded the highest values after 30 minutes of incubation, before declining rapidly. The South African unimproved indigenous bucks seem to produce a lower semen volume (ejaculate), sperm concentration, and percentage progressively motile sperms, compared to the European, Asian and Boer goat breeds. The results demonstrate that Bioxcell and Ovixcell are suitable extenders to induce high post-thawing viability, motility and velocity of buck sperm.