Abstract:
Isomers of conjugated linoleic acid (CLA) enhances circulating insulin-like growth factor I
(IGF-I) levels. Furthermore, fertility rate of breeding bulls is positively correlated to seminal plasma
IGF-I concentration. Our objective was to evaluate the effect of dietary CLA supplementation and
inclusion to the semen extender on bovine semen quality and freezability. Fourteen bulls, randomly
assigned to control (CTL) and CLA (50 g/day) groups, were supplemented for 10 weeks. Samples
were collected at Weeks −2 (before supplementation), 0, 4, 6 (during supplementation), 10, and 11
(after supplementation). Blood and seminal plasma were analyzed for IGF-I; the ejaculates were
frozen in the following subgroups: CTL (no addition to semen extender), CLA c9, t11 (50 µM), CLA
c9, t11 (100 µM), CLA t10, c12 (50 µM), CLA t10, c12 (100 µM), and CLA mix (50 µM each of CLA c9,
t11 and CLA t10, c12). Sperm motility, morphology, viability, mitochondrial membrane potential, and
reactive oxidative species were assessed. CLA supplementation decreased ejaculates’ total volume,
increased sperm concentration, beat cross frequency, and decreased oxidative stress; it also increased
plasma and seminal plasma IGF-I levels compared to the CTL. The inclusion of CLA c9, t11 100 µM
and CLA mixture in the extender increased live spermatozoa percentage post-thawing compared
to other groups. Our results show a beneficial effect of CLA supplementation on semen quality;
however, further studies evaluating fertilization rates are necessary to corroborate the results.
