Effect of semen extender and storage temperature on motility of ram spermatozoa following liquid storage

Authors: ACHARYA, MOHAN - University Of Arkansas; Burke, Joan; RORIE, RICK - University Of Arkansas

Submitted to: Advances in Reproductive Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/16/2019
Publication Date: 12/16/2019
Citation: Acharya, M., Burke, J.M., Rorie, R.W. 2019. Effect of semen extender and storage temperature on motility of ram spermatozoa following liquid storage. Advances in Reproductive Sciences. 8(1):14-30.

Interpretive Summary: Artificial insemination of ewes allows for use of high quality genetics, but use of conventional frozen semen results in low conception rates. Use of extended chilled semen may increase conception rates, but optimization of extenders and storage temperatue is needed. Scientists from the Agricultural Research Service - Booneville, AR and University of Arkansas determined that a milk based or a TRIS buffer based extender stored at 4°C for up to 24 hours yielded acceptable sperm motility. More research on use of these extenders for artificial insemination is needed. This information is important to sheep producers, scientists, veterinarians, and extension specialists aiming to improve reproductive performance and genetic selection in sheep.

Technical Abstract: Freeze-thaw process of ram semen results in low survival of spermatozoa; thus, efforts are underway to optimize liquid-storage of chilled semen. In Exp. 1, semen collected from each ram (n = 5) was divided into four aliquots and extended using one of the following: 1) milk, 2) TRIS (tris[Hydroxymethyl]aminomethane), 3) TEST (N-Tris(hydroxymethyl)-methyl-2-aminoethane sulfonic acid), and 4) CJ-2 (choline-based extender) and stored at 4°C and 15°C. All extenders were supplemented with 5% (v/v) egg yolk. In Exp. 2, semen collected from 9 rams was distributed across treatment combinations consisting of either TRIS or milk extenders supplemented with 5% or 20% (v/v) egg yolk, ± ethylene glycol (EG), and ± penicillamine, hypotaurine, and epinephrine (PHE), and stored at 4°C for 72 hours. In Exp. 1, most of the sperm motility parameters were higher after extension, and when stored at 4°C compared with 15°C (P < 0.05). Ram semen extended using milk or TRIS based extenders and stored at 4°C maintained similar sperm progressive motility, but were higher compared with TEST or CJ-2 extenders (P < 0.05). However, progressive motility of ram sperm declined by 75% when stored at 4°C for 24 hours, and continued to decline over time regardless of extender used. In Exp. 2, milk extender supplemented with 1% EG and 20% egg yolk before storage and addition of PHE before analysis had higher sperm motility parameters than other extender and supplement combinations. Further studies are needed to examine sperm fertility using these extenders and supplements in vivo using artificial insemination in ewes.