EFFECT OF HOMOLOGOUS AND HETEROLOGOUS SEMINAL PLASMA ON THE FERTILIZING ABILITY OF EJACULATED BULL SPERMATOZOA ASSESSED BY PENETRATION OF ZONA-FREE BOVINE OOCYTES
Ma. Henault et Gj. Killian, EFFECT OF HOMOLOGOUS AND HETEROLOGOUS SEMINAL PLASMA ON THE FERTILIZING ABILITY OF EJACULATED BULL SPERMATOZOA ASSESSED BY PENETRATION OF ZONA-FREE BOVINE OOCYTES, Journal of Reproduction and Fertility, 108(2), 1996, pp. 199-204
The ability of seminal plasma to influence the fertility of ejaculated
bull spermatozoa was examined using a sperm penetration assay for zon
a-free bovine oocytes. Washed, ejaculated spermatozoa from bulls of be
low (low) or above average (high) fertility were mixed with seminal pl
asma from the same bull, or with seminal plasma from a bull of contras
ting fertility. Treated spermatozoa were stained with different fluoro
chromes and competed to penetrate oocytes after heterospermic insemina
tion in vitro. Washed spermatozoa exposed to seminal plasma from bulls
of high fertility penetrated more oocytes than those spermatozoa mixe
d with seminal plasma from bulls of low fertility (P < 0.01). Mixing l
ow fertility spermatozoa with high fertility seminal plasma generally
improved penetrating ability compared with low fertility spermatozoa m
ixed with low fertility seminal plasma (P = 0.05). Washed spermatozoa
from a bull of low fertility mixed with his own seminal plasma had gre
ater ability to penetrate oocytes than did washed spermatozoa from a b
ull of high fertility mixed with seminal plasma from a bull of low fer
tility (P < 0.01). The bias associated with using low fertility semina
l plasma from the bull providing the spermatozoa was removed by repeat
ing this experiment using pooled seminal plasma from different subfert
ile bulls. After combination with pooled seminal plasma from bulls of
low fertility spermatozoa from bulls of high or low fertility penetrat
ed oocytes in a similar way, but high fertility spermatozoa had a slig
htly higher penetration rate (P = 0.12). In conclusion, the penetratio
n of zona-free oocytes by ejaculated spermatozoa from bulls of low fer
tility was marginally improved by seminal plasma from bulls of high fe
rtility, but penetration by high fertility spermaotoza was decreased b
y exposure to low fertility seminal plasma. Seminal plasma from bulls
of low fertility similarly affected the penetrating ability of high an
d low fertility spermatozoa if the seminal plasma used was foreign to
the spermatozoa being tested.