Characterization and cryopreservation of South African unimproved indigenous goat semen

[摘要] Semen from 7 South African unimproved indigenous bucks that were successfully trainedfrom a group of 10 bucks for semen collection with the aid of an artificial vagina (AV) wascharacterized and then cryopreserved, using different semen extenders. Semen was collectedtwice a week and evaluated macroscopically for ejaculate volume and pH immediately aftercollection. Within 1h of collection, semen was further analysed electronically for spermconcentration. Thin semen smears were stained with eosin/nigrosin and evaluated under afluorescent microscope for viability (percentage live or dead) and morphology (percentagenormal or abnormal). In addition semen samples were evaluated using the computer assistedsperm analysis (CASA) for sperm motility (static, non progressive and progressive),velocities (static, slow, medium, rapid, VCL, VSL and VAP) and linearity (LIN, STR andWOB) parameters using a Sperm Class Analyser® (SCA®).Four different semen extenders, namely: Tris-1.5% yolk, Tris-15% BSA, Ovixcell® andBioxcell® (IMV, L'Aigle, France) were used to cryopreserve pooled semen samples, with andwithout 6% glycerol thus making a total of 8 treatments. Immediately after dilution and afterthawing, 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 30and 60 minutes of incubation.Regarding the fresh semen samples, the South African unimproved indigenous bucksrecorded an overall average ejaculate volume of 0.5 ± 0.2 ml, pH of 7.5 ± 0.2 and spermconcentration 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 spermabnormalities 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, nonprogressivelymotile (NPM), progressively motile (PM), slow, medium and rapid sperm cellsrecorded 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 semenextenders was similar, however a reduction of approximately 20% in the percentage live andnormal sperm was recorded (5-10 minutes after dilution), when compared to the freshundiluted pooled semen sample. Similar motility parameters were recorded shortly after freshsemen dilution using the 4 different extenders. A slight decrease of approximately 4% in theextended semen's sperm motility was observed, when compared to that of fresh undilutedsemen. For the sperm velocity parameters, semen extended in Tris-BSA showed significantlyhigher medium sperm velocity.Following freezing-thawing, a drastic reduction in the percentage live and normal sperm wasrecorded in all treatments. Bioxcell® without glycerol recorded the highest number of live andnormal sperm. The Bioxcell® and Ovixcell® extenders recorded the highest percentagelinearity and straightness movement of the sperm. In general, cryopreservation reduced thesperm cell viability and motility parameters. In addition no effect of extender on themorphology of South African unimproved indigenous buck sperm was observed. Spermmotility and velocity results showed that sperm extended in Bioxcell® and Ovixcell® recorded higher values immediately post-thawing, while the Tris-based extenders recorded the highestvalues 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 tothe European, Asian and Boer goat breeds. The results demonstrate that Bioxcell andOvixcell are suitable extenders to induce high post-thawing viability, motility and velocity ofbuck sperm.

[发布机构] University of the Free State