Modification of endometrial fatty acid concentrations by the pre-implantation conceptus in pasture-fed dairy cows

The current study determined whether the pre-implantation conceptus modified endometrial fatty acid concentrations. Oestrus was synchronized in 14 mature lactating cows and embryos were transferred on day 7. Cows were slaughtered 10 d later, with each uterine horn flushed, the pre-implantation conceptus located, and inter-caruncular endometrial tissue collected from the gravid horn (containing the pre-implantation conceptus) and non-gravid horn. Endometrial fatty acid concentrations in the gravid and non-gravid horn were compared using linear models in restricted maxiumum likelihood. Investigations of the correlations among selected fatty acids and trophoblast weight or uterine fluid interferon-tau (IFN-τ) concentrations were also undertaken. The presence of the pre-implantation conceptus had relatively minor effects on endometrial fatty acid concentrations, but the ω6:ω3 ratio was greater and concentrations of stearic and oleic acid were slightly increased in the gravid horn. In the gravid horn, a negative linear relationship between the concentration of arachidonic acid and conceptus weight and IFN-τ concentration in the uterine luminal fluid were observed. In contrast, there was a positive relationship between concentrations of dihomo-γ-linolenic acid in the non-gravid horn and conceptus weight. In conclusion, the presence of the pre-implantation conceptus appears to modulate endometrial fatty acids, as indicated by the differences in endometrial fatty acid concentrations in the gravid and non-gravid uterine horns. The physiological implication of these local effects of the pre-implantation conceptus, on reproductive success requires further investigation.