The redilution of deep frozen bull semen

Abstract

ABSTRACTWith deep frozen bull semen processed in an egg yolk – milk diluent and stored in plastic straws at — 196°C, a lowering of the dose rate from 25 million (3824 inseminations) to 12·5 million total sperm per insemination (3900 inseminations) resulted in a decline in conception rate (CR = 49-day non-return rate) of 6·5 % (60·1v.53·6). Development of a processing technique which allowed sperm to be stored at — 196°C at concentrations of 450 or 100 million sperm per ml prior to subsequent rapid thawing and redilution (RDF) allowed dose rates to be reduced to around 5 million total sperm per insemination without any significant reduction in CR. The re-diluted semen was used for inseminations made from 4 to 8 h after thawing and redilution. The use of RDF procedure could reduce semen storage costs, increase the number of inseminations per sire, and has potential application in oestrus synchronization programmes or in countries with developing insemination programmes.