The Equine Blood Fatty Acid Profile and Clearance Rate of Supplemented Fatty Acids

An optimal equine blood fatty acid (FA) profile has not been defined, nor has a general baseline profile been established. Further, there is little information on the clearance rate of FAs in plasma and red blood cells (RBCs) after supplementation ends. Data from 4 studies were compiled to evaluate the baseline FA profile in horses fed varied diets without FA supplementation for at least 6 mo (n = 68). Sample handling and processing were performed identically in all studies and 24 FAs were quantified using gas chromatography. A subset of data (n = 18) was used to evaluate how eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA) affects the FA profile during and after 3 mo of supplementation (4.3–8.7 g EPA+DHA/d). Data were analyzed for mixed-effects. Baseline plasma FA profile included primarily linoleic acid (LA; 49.49% mean; 95% CI [48.32, 50.65]), stearic acid (15.90%; [15.61, 16.19]), palmitic acid (13.99%; [13.59, 14.38]), and oleic acid (10.66%; [10.12, 11.20]). Other FAs included arachidonic acid (AA; 0.94%; [0.87, 1.01]), EPA (0.14%; [0.12, 0.16]), and DHA (0.16%; [0.14, 0.19]). Baseline RBC profile differed slightly, primarily made up of LA (37.47%; [36.76, 38.17]), oleic acid (20.20%; [19.92, 20.47]), stearic acid (17.40%; [17.09, 17.71]), and palmitic acid (14.86%; [14.53, 15.20]). Other FAs included AA (1.23%; [1.18, 1.29]), EPA (0.19%; [0.16, 0.22]),and DHA (0.21%; [0.18, 0.24]). Plasma EPA and DHA increased 277% (0.41%; [0.29, 0.54]; P < 0.001) and 223% (0.56%; [0.40, 0.73]; P < 0.001), respectively, within 1 mo of supplementation and returned to baseline levels (P = 0.98) by 1 mo post-supplementation. RBC EPA and DHA increased 178% (0.37%; [0.29, 0.44]; P < 0.0001) and 102% (0.37%; [0.31, 0.44]; P < 0.0001), respectively, within the first month of supplementation and continued to climb 313% (0.63%; [0.46, 0.79]; P < 0.001) and 197% (0.70%; [0.55, 0.85]; P < 0.001) by the third month, respectively. RBC EPA returned to baseline (P = 0.21) by 3 mo post-supplementation, but RBC DHA had still not returned (P < 0.05). Compared with plasma, RBCs showed gradual changes over time and required significantly more time to appropriately wash out. Additionally, the clearance rate may differ between fatty acids. Plasma values are more commonly reported than values for RBC or other tissues. These data suggest RBC values may be important to consider and that appropriate washout durations from previous FA supplementation may be longer than expected. Further research is needed to evaluate other tissue affected by FA supplementation and how long the FA profile may be altered.