CONCLUSION
Cryopreservation is the only method through which
spermatozoa form genetically superior elite bulls can be
preserved at –196ºC in the liquid nitrogen. The frozen
semen can safely and easily be transported to the remotest
parts of the world. The most important need of the tropical
developing countries like Nigeria and Pakistan is a suitable
extender and preservation technique in which spermatozoa
can be preserved at –196ºC without loosing their fertilizing
ability. Extenders containing lactose-egg yolk glycerol
showed better performance during laboratory evaluation,
but milk-egg yolk glycerol extender gave higher conception
rate when frozen semen was inseminated. Thawing at 37ºC
for 10 seconds gave higher fertility than 20ºC for one
minute or 5ºC for 2 seconds. Further studies in this area
study investigate the effects of nutrition and other
environmental factors on the fertility of post-thawed semen
in the tropical developing countries.