Efforts to correlate laboratory with field observations on bull sperm fertility.

This work represents efforts towards development of the zona-free hamster ovum sperm penetration assay for predicting relative levels of fertility for semen from individual bulls. Results reported here followed insemination of hamster vitelli with bull sperm, after frozen storage, with observations of sperm acrosomes and parallel inseminations of more than 1000 cows with semen from each bull. The average 75-day non-return rate for the four bulls was 74.0% (range 71.6 to 75.6). Laboratory studies indicated the following: the percentage of sperm with intact acrosomes varied from 55 to 73 between bulls, the percentage of motile sperm varied from 41 to 64, the percentage of sperm with progressive motility ranged from 24 to 40, the number of sperm interacting per (zona-free hamster) ovum ranged from 1.6 to 3.8, the number of sperm attached per ovum ranged from 1.4 to 2.9, the number of sperm within each penetrated ovum ranged from 1.5 to 1.8, the percentage of ova interacting with sperm ranged from 76 to 92, the percentage of ova penetrated ranged from 62 to 85, and the percentage of ova with male pronuclei ranged from 33 to 49. Although predictive ranking in the laboratory of these bulls with less than 4% variation in fertility levels was not possible, the zone-free hamster ovum test could be useful in identifying potentially subfertile bulls before they enter a young sire-sampling program.

Normal development following in vitro fertilization in the cow.

A repeatable procedure for fertilization of bovine ova in vitro is described. Oocytes were recovered from ovarian follicles or from oviducts near the time of ovulation following treatment of donors with pregnant mare's serum gonadotropin (PMSG) and prostaglandin F2 alpha (PGF2 alpha). For in vitro capacitation semen was incubated, then high ionic strength treated and subsequently incubated in defined medium prior to insemination of oocytes. In one experiment frozen bull semen was successfully used. In experiments with 4 bulls (B, C, D, F), 34 (43.6%) of 78 ova and 13 (19.7%) of 66 follicular oocytes were fertilized in vitro. In the last series (spermatozoa from Bull F) the fertilization of 22 (62.9%) of 35 tubal ova was achieved. In vitro development proceeded to the 8-cell stage. No fertilization in vitro followed use of one male (Bull E), even though his spermatozoa could penetrate zona-free hamster ova in vitro, and higher than usual bacterial contamination of his semen was implicated as the probable cause. Findings suggested vigorous progressive sperm motility and acrosome integrity to be important features of good sperm samples. In one experiment a 4-cell stage embryo was transferred with the result that the recipient gave birth to a normal bull calf on June 9, 1981. The first calf resulting from in vitro fertilization has been found to be completely normal.