The role of low density lipoproteins as based extender in bovine semen cryopreservation and its effect on fertility

Abstract EN

The aim of the current study was to evaluate the cryopreservation effect of different concentrations of low density lipoproteins (LDL) (4, 6, 8 and 10%), as a substitute for whole egg yolk (20%) in Holstein bull semen extender and its effect on bull semen freezing and subsequent fertility.

Semen was collected from four bulls twice weekly for 12 weeks and the ejaculates with more than 75% progressive motility and 85% normal morphology were pooled prior to cryopreservation.

Semen was diluted at 37ºC with Tris-citric acid extender to 8×107 motile spermatozoa/ml.

Diluted semen was equilibrated at 4ºC for 4h., filled in 0.25 ml French straws and kept on liquid nitrogen vapors for 10 min.

Straws were plunged and stored in liquid nitrogen (-196ºC).

Sperm motility, plasma membrane integrity and acrosome integrity were assessed at post-dilution, pre-freezing and post freezing-thawing.

Results revealed that the 6% LDL concentration in semen extender was more effective (P<0.05) in preservation of progressive motility, plasma membrane integrity and acrosome integrity of spermatozoa than control and the other LDL concentrations (8 and 10%) at different cryopreservation processes.

Fertility rates were higher (P<0.05) in cows artificially inseminated with the semen cryopreserved in 4 and 6% LDL extenders (72.7 and 76.7%) compared with that of control, 8 and 10% LDL extenders (60 , 61.5 and 58.3%, respectively).

It could be concluded that the 6% LDL concentration in the extender was better able to protect the bovine sperm cell from cryodamage and improved cryopreserved semen quality and fertility.