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Our objectives were to determine 1) the concentration of prostaglandin
F2α (PGF2α) in whole and extended bovine semen, 2) if concentrations of
prostaglandins in extended bovine semen are correlated to fertility, and 3) if PGF2α
administered at the time of artificial insemination would improve conception rate.
Concentration of PGF2α tended to be only slightly greater for whole compared to
extended semen. To elucidate why PGF2α levels were comparable, semen was
extended at eight dilution rates. Prostaglandin F2α in sub-samples, collected during
extension, decreased at higher dilution rates and later steps of extension. To quantify
PGF2α synthesized during extension, quantities of PGF2α in semen and the diluent
were subtracted from each step. Higher dilution rates reduced the final amount of
PGF2α synthesized. Initial PGF2α concentration was greater in whole semen compared
to seminal plasma; however, when extended at three dilution rates quantity of PGF2α
synthesized during extension was greater for semen compared to seminal plasma,
indicating less disparity than for original samples. Concentrations of prostaglandin E2
(PGE2) and PGF2α in extended semen and the ratio of PGE2 to PGF2α were compared
to a fertility rating. The ratio of PGE2 to PGF2α was not correlated to the fertility
rating. Semen was extended to contain either 0, 500, or 5000 pg/ml of exogenous
PGF2α. Exogenous PGF2α did not affect post-thaw motility or proportion of normal
spermatozoa. In vitro fertilization did not differ between treatments. Analysis of
cleavage rate per embryo revealed a bull x semen treatment interaction. First service
conception rate of cows inseminated with the PGF2α-enhanced semen was affected by
semen treatment and technician. Beef heifers inseminated with subfertile semen and
dairy cows inseminated with normal fertility semen and treated with PGF2α after
insemination displayed higher conception rates compared to control animals. These
data suggest that, although extension reduces the concentration of many seminal
components, PGF2α synthesis during extension results in concentrations similar to
whole semen. Seminal prostaglandin concentrations may be related to fertilizing
capability of the semen, and exogenous PGF2α administered at the time of
insemination may improve conception rate. |
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