Effect of semen dilution to low-sperm number per dose on motility and functionality of cryopreserved bovine spermatozoa using low-density lipoproteins (LDL) extender: Comparison to Triladylp and Bioxcellp

摘要

Artificial insemination with doses containing low-sperm numbers has been utilized to optimize the use of elite bulls. Hen egg yolk is widely used as a cryoprotective agent in semen freezing extender protecting the spermatozoa. Its action is due to the presence of low-density lipoproteins (LDL) in the hen egg yolk. The objectives of the present study were to evaluate the effects of the semen dilution to low-sperm number/dose on sperm motility and integrity of sperm plasma membrane in the cryopreservation process, using two commercial extenders (Triladylp, Bioxcellp) and LDL extender prepared in our laboratory, 97% purity. Fifteen ejaculates were collected from five fertile crossbred bulls (Bos taurus x Bos indicus). After collection, sperm motility was examined by Computer-Assisted Semen Analysis (Hamilton Thorne), morphological sperm characteristics were evaluated by differential interference microscopy and the integrity of plasma membranes was determined using the hypo-osmotic swelling test. The semen was subsequently divided into three aliquots and diluted with the three extenders into 120x10e, 60x10e and 20x10e sperm/mL, corresponding to 30x10e, 15x10e and 5x10e sperm/dose, respectively. This study revealed that LDL extender was more effective in preservation of motility and integrity of the plasma membrane of spermatozoa than Bioxcellp and Triladylp (p <0.05), but no significant difference was observed between Triladylp and Bioxcellp. Therefore we can conclude that LDL extender could be used instead of Triladylp or Bioxcellp at low semen concentration per dose for elite bulls, it also could be envisaged for the industry of sex-stored semen.