PS11-15. Fatty Acid Composition in Plasma, Red Blood Cells and Endometrium of PBIE-susceptible Mares Before and After Oral omega-3 DHA Supplementation.

Abstract Persistent breeding-induced endometritis (PBIE) is associated with a dysregulated post-breeding inflammatory response and reduced fertility in mares. Standard intra-uterine treatments address uterine clearance and inflammation, but the effect of oral n-3 fatty acid supplementation on PBIE has not been evaluated. In previous studies, n-3 fatty acid supplementation improved oocyte recovery, embryo recovery, and pregnancy rates in cows, resulted in faster postpartum uterine involution in mares, and modulated chronic inflammatory conditions in horses. It is necessary to understand how DHA supplementation alters fatty acid composition in the blood and reproductive tissues of PBIE-susceptible mares if it will be used as an anti-inflammatory treatment. The objective of this study was to evaluate fatty acid composition in plasma, red blood cells (RBC), and endometrial tissue of PBIE-susceptible mares before and after oral omega-3 DHA supplementation. Twelve mares classified as susceptible to PBIE were sampled immediately before and following six weeks of oral omega-3 DHA supplementation (40 mL/day; OmegaPrime+, Mad Barn Inc, 25% DHA). Samples included whole blood for plasma and RBC fatty acid analysis (n = 12) and endometrial biopsies in a subset of mares (n = 4). Fatty acid composition was determined by lipid extraction followed by gas chromatography. Endometrial tissue phospholipids were separated by thin-layer chromatography and subsequently analyzed by gas chromatography. Pre- and post-supplementation values were compared using paired t-tests or Wilcoxon signed-rank tests. After supplementation, the proportion of DHA increased in plasma (0.24 ± 0.29% vs. 1.17 ± 0.42%; p < 0.001). Arachidic acid (p = 0.017), behenic acid (p < 0.001), tricosenoic acid isomers (p < 0.001), docosadienoic acid (p = 0.032), and lignoceric acid (p = 0.017) also increased. Conversely, α-linolenic acid (p = 0.023) and docosapentaenoic acid n-3 (0.13 ± 0.07% vs. 0.07 ± 0.10%; p = 0.004) decreased after supplementation. In the endometrium, DHA was increased in the phosphatidylcholine fraction (p = 0.05), while lysophosphatidylcholine dihomo-γ-linolenic acid decreased after supplementation (p = 0.009). No significant differences were detected in RBC between pre- and post-supplementation samples. Oral supplementation with omega-3 DHA changed the composition of plasma fatty acids, increased circulating DHA, and resulted in DHA enrichment in the endometrium, as reflected by changes in phosphatidylcholine fatty acid composition. Given that PBIE results from dysregulation of the local uterine inflammatory response after breeding, modification of endometrial lipid composition through DHA supplementation provides a rationale for its use as a potential anti-inflammatory strategy in susceptible mares.