Effects of Continuous and Alternating Storage Temperatures of −79 and −196° C. on Motility of Frozen Bull Semen

Abstract

Seventeen ejaculates from 12 bulls were frozen and divided equally for storage in dry ice-alcohol and liquid nitrogen. Portions of each ejaculate from each storage temperature were thawed and estimated for per cent progressive motility immediately after freezing and after 1,2,3,4,6,8,10,12,14,16 and 18 weeks of storage. Transfers of paired samples were made from one storage temperature to the other after 6 weeks continuous storage at their respective temperatures. Following motility estimations at 2,4 and 6 weeks post transfer, the remaining samples were retrans-ferred to their original storage temperature for a similar 2,4 and 6 week evaluation. A highly significant difference in motility (P<0.001) was found between continuous liquid nitrogen and dry ice-alcohol storage in favor of the colder temperature. Semen transferred from -196[degree]C to -79[degree]C showed an immediate decline in motility similar to that observed during the initial 2 week dry ice-alcohol storage period. Motility of semen transferred from -79[degree]C to -196[degree]C fell slightly below the motility of continuous dry ice-alcohol storage. Slight motility declines were noted in both retransfers to the original storage temperature.