Arav, A., Institute of Animal Science, Agricultural Research Organization, The Volcani Center, Bet Dagan 50250, Israel
Zeron, Y., Institute of Animal Science, Agricultural Research Organization, The Volcani Center, Bet Dagan 50250, Israel
Shturman, H., Institute of Animal Science, Agricultural Research Organization, The Volcani Center, Bet Dagan 50250, Israel
Gacitua, H., Institute of Animal Science, Agricultural Research Organization, The Volcani Center, Bet Dagan 50250, Israel

The objective of the following paper is to describe a new technology for large volume and double freezing of semen in 12 mL test tubes. Semen from two different bulls was frozen with a new technique using 12 mL test tubes and was refrozen after thawing in mini straws. All freezing was done in a "Multi thermal gradient" (MTG) freezing apparatus, which moves the container at a constant velocity (V) through a thermal gradient (G) producing a controlled cooling rate B = (G) × (V). Each of the two bulls ejaculated were evaluated for post thaw motility in the lab and then in a field trial which was carried out in a split sample mode. We inseminated 105 cows after a double freezing/thawing cycle, and another 123 cows were inseminated with semen frozen in mini-straws and a conventional method. The results showed a 75 ± 5% post thaw motility after freezing a 12 mL test tube and 50 ± 5% after a second freezing/thawing in mini-straws, respectively. Controlled vapour freezing showed a 60 ± 10% post thaw motility. The results of the field trial showed a pregnancy rate of 44% (47/105) for the double freezing group in comparison to 45.5% (56/123) for the controlled group. These results can be beneficial for large volume freezing, and therefore for bull semen cryobanking in a large volume which will be followed by second freezing in a regular insemination volume.