Deep Freezing of Boar Semen Packaged in Plastic Bags and Straws

Abstract

Contents: For practical reasons, a large volume (i.e. 5 ml) of frozen boar semen per insemination dose is desirable, but successful freezing has not been achieved, since optimal cooling rates have not yet been established. Post‐thaw motility and the acrosome intep'ty of semen from four boars frozen with a programmable freezin machine, in mini‐(0.25 ml), maxi‐(5 ml) plastic straws and in 10 × 5 cm PVC‐ or Teflon FEP‐plastic bags (0.35 – 0.12 mm thick, 5 ml) was studied. The freezing of the semen was monitored using thermocouples placed in the straws and the bags. The freezing curve started from +5°C, at a rate of −3°C/min, to – 6°C, it was held for 1 min at −6°C, and was followed by further drop to −100°C at a rate of −20°C/min, with subsequent storage in LN 2 . The bags had a much shorter freezing point plnteau, compared to the maxi‐straws. Post‐thaw sperm motility was significantly higher when semen was frozen in mini‐straws or in bags than in maxi‐straws. The freezing procedure did not cause major acrosomal damages, significantly more normal apical ridges being present in the bags and mini‐straws than in the maxi‐straws. This in vitro evaluation indicates that the freezing method employed is satisfactory for freezing large volumes of boar semen into plastic bags .