Motility and Membrane Integrity of Ejaculated Bovine Spermatozoa Extended and Cryopreserved in L-carnitine Tris-egg Yolk Extender

This study was conducted to examine if L-carnitine supplementation in the Tris-egg-yolk extender can improve the motility characteristics, membrane integrity, and in vitro fertilization potential after cryopreservation of ejaculated bovine spermatozoa. It was carried out on January to May 2013 at the University of Wisconsin-Madison. L-carnitine at final concentrations of 0.5, 1, 10, and 30mM were added to Tris-egg yolk extender where semen was suspended at 100x10 sperm cells/mL. Tris-egg yolk without carnitine served as control. Motility characteristics and functional integrity of membrane were examined by computer assisted sperm analysis and hypo-osmotic swelling test at 2, 6, and 24 hour at room temperature. The post-thaw effect of L-carnitine was likewise assessed. Each treatment suspension was cryopreserved in Tris-egg yolk with 7% glycerol, stored in liquid nitrogen and subjected to computer assisted sperm analysis and hypo-osmotic swelling test post-thawing. Lastly, the fertilization potential of frozen semen treated with L-carnitine was used for in vitro fertilization and cleavage and blastocyst development were assessed. L-carnitine was demonstrated to improve the motility characteristics in a concentration-depended manner; 1mM concentration is efficient but high concentration beyond 30mM had cytotoxic effect. A similar trend was observed on membrane integrity although significant difference was not evident. After IVF, the use of 1 mM L-carnitine resulted in significantly higher cleavage rate (92.4% vs. 82.8%) suggesting that L-carnitine supplementation at low concentration in Tris-egg yolk extender improves motility and fertilization potential of bovine sperm cells.