<p class="first" id="d6181580e93">The positive effect of n-3 polyunsaturated fatty
acids (FAs) on fertility in ruminants
seems to be partly mediated through direct effects on the oocyte developmental potential.
We aimed to investigate whether supplementation with physiological levels of docosahexaenoic
acid (DHA, C22:6 n-3 polyunsaturated fatty acids) during IVM has an effect on oocyte
maturation and in vitro embryo development in cattle. We reported that DHA (0, 1,
10, or 100 μM) had no effect on oocyte viability or maturation rate after 22-hour
IVM. Incubation of oocyte-cumulus complexes with 1-μM DHA during IVM significantly
increased (P < 0.05) oocyte cleavage rate as compared with control (86.1% vs. 78.8%,
respectively) and the greater than 4-cell embryo rate at Day 2 after parthenogenetic
activation (39.1% vs. 29.7%, respectively). Supplementation with 1 μM DHA during IVM
also induced a significant increase in the blastocyst rate at Day 7 after IVF as compared
with control (30.6% vs. 17.6%, respectively) and tended to increase the number of
cells in the blastocysts (97.1 ± 4.9 vs. 81.2 ± 5.3, respectively; P = 0.08). On the
contrary, 10-μM DHA had no effects, whereas 100-μM DHA significantly decreased the
cleavage rate compared with control (69.5% vs.78.8%, respectively) and the greater
than 4-cell embryo rate at Day 2 after parthenogenetic activation (19.5% vs. 29.7%).
As was shown by real-time polymerase chain reaction, negative effects of 100-μM DHA
were associated with significant increase of progesterone synthesis by oocyte-cumulus
complexes, a three-fold increase in expression level of FA transporter CD36 and a
two-fold decrease of FA synthase FASN genes in cumulus cells (CCs) of corresponding
oocytes. Docosahexaenoic acid at 1 and 10 μM had no effect on expression of those
and other key lipid metabolism-related genes in CC. In conclusion, administration
of a low physiological dose of DHA (1 μM) during IVM may have beneficial effects on
oocyte developmental competence in vitro without affecting lipid metabolism gene expression
in surrounding CCs, contrarily to 100 μM DHA which diminished oocyte quality associated
with perturbation of lipid and steroid metabolism in CC.
</p>