E Kommisrud1,2, G Klinkenberg3, L Bekk1, AH Alm-Kristiansen1 1SpermVital AS, Hamar, Norway 2Hedmark University College, Hamar, Norway 2SINTEF Industrial Biotechnology, Trondheim, Norway
Shelf life of spermatozoa has been prolonged using immobilization preserving techniques, demonstrated on liquid semen as well as on cryopreserved semen, both in vitro and in vivo. The techniques have been applied successfully in the bovine, ovine, equine and porcine. Sperm cells are immobilized in alginate gels, due to interactions between divalent ions such as Ca2+ and block structures of the guluronic acid in the alginate polymer chain. The cells are thus embedded in a solid gel network, this being in contrast to encapsulation techniques leaving the cells in a liquid core surrounded by a membrane. Upon artificial insemination (AI) or application in artificial media, the gel will gradually dissolve, then releasing sperm cells over a prolonged period. In vitro trials have demonstrated that gels with immobilized sperm may dissolve both fast and slow, depending on the media composition. Several studies have been conducted to demonstrate dissolving time, prolonged survival of both immobilized and released sperm cells, as well as reduced metabolism of immobilized spermatozoa. Quality control in vitro includes e.g. viability, acrosome integrity and DNA integrity. In vivo trials, conducted as AI field trials on several thousand heifers and cows, have demonstrated that immobilized spermatozoa increase fertility in the Holstein breed, whereas in the highly fertile Norwegian Red double inseminations with ordinary processed semen can be replaced by one single insemination with immobilized semen obtaining equal pregnancy rates. (Further, filed trials have demonstrated that timing of AI is less critical using immobilized semen.) The immobilization technology on sperm cells was developed to make AI an even more valuable breeding method, by improving fertility results and making AI more flexible. The technology is described in patent application PCT/NO07/00256, and is commercialized by the company SpermVital AS. An early version of the product has been launched in several cattle AI markets. Continuous research is performed by the company, having improved versions in the pipeline, and aiming at application in several species, including humans.