IN-VITRO FERTILIZING CHARACTERISTICS OF BOVINE SPERMATOZOA WITH MULTIPLE NUCLEAR VACUOLES - A CASE-STUDY

A study was designed to determine the in vitro fertilizing characteris tics of bovine semen with a high percentage of spermatozoa with multip le nuclear vacuoles. In Experiment 1, a total of 620 oocytes was divid ed into 2 groups and inseminated with spermatozoa from 1 of 2 differen t bulls at a concentration of 2x10(5)/ml. After Percoll washes, 73.5+/ -3.0% of spermatozoa from Bull A contained multiple nuclear vacuoles, while no sperm cells from Bull B contained vacuoles. After 19.5+/-0.5 h of co-incubation of oocytes with spermatozoa, loosely attached sperm cells were removed by washing, and the oocytes were fixed between 2 p oly-l-lysine coated glass slides. Mean (+/-SD) percentage of fertiliza tion was significantly lower (P<0.05) in Bull A (19.7+/-7.0%) than in Bull B (67.6+/-4.5%). In one-third of the oocytes fertilized by sperma tozoa from Bull A, sperm head decondensation was incomplete and normal male pronucleus formation did not occur. All oocytes fertilized by Bu ll B had normally decondensed sperm heads. Although fewer (P<0.05) spe rmatozoa from Bull A were bound to the zona pellucida than from Bull B , the percentage of vacuolated sperm cells bound to the zona pellucida (73.3+/-7.8%) did not differ from that in the inseminate. The mean nu mber of sperm cells binding to fertilized oocytes was higher than to u nfertilized oocytes for both bulls (P<0.05). In Experiment 2, 748 salt -stored oocytes (zonae) were inseminated with semen from the same 2 bu lls to determine the ability of spermatozoa to penetrate the zona pell ucida. The percentage of zonae penetrated by spermatozoa from Bull A ( 69.9+/-3.5%; a mean of 2.4+/-2.3 spermatozoa) was lower (P<0.05) than from Bull B (96.5+/-14.7%; a mean of 11.3+/-9.9). Although the proport ion of vacuolated sperm cells from Bull A that bound to the zona pellu cida did not differ from that in the inseminate, the proportion of tho se penetrating the zona pellucida (52.7%) was lower (P<0.05). In summa ry, vacuolated sperm cells apparently gained access to the oocyte and bound to the zona pellucida, but they penetrated the zona pellucida at a lower rate and apparently did not form normal male pronuclei.