44 Evaluation of conjugated linoleic acid supplementation on markers of joint inflammation and cartilage metabolism in young horses challenged with lipopolysaccharide (LPS)

s / Journal of Equine Veterinary Science 35 (2015) 400e417 403 44 Evaluation of conjugated linoleic acid supplementation on markers of joint inflammation and cartilage metabolism in young horses challenged with lipopolysaccharide (LPS) A.N. Bradbery*, J.A. Coverdale , K.L. Vernon , J.L. Leatherwood , C.E. Arnold , R.A. Dabareiner , M.K. Kahn , A.A. Millican , T.H. Welsh, Jr. , and S.B. Smith 1 1 Texas AM 2 Clemson University, Clemson, SC, USA; 3 Sam Houston State University, Huntsville, TX, USA Seventeen yearling Quarter horses were used in a randomized complete block design for a 56-d trial to determine the ability of dietary conjugated linoleic acid (CLA) to reach detectable circulating levels in plasma and synovial fluid, to mitigate joint inflammation and alter cartilage turnover. Horses were blocked by age, sex and BW and randomly assigned to treatments consisting of a commercial concentrate offered at 1% BW (as-fed) supplemented with either 1% soybean oil (CON; n 1⁄4 6), 0.5% soybean oil and 0.5% CLA (LOW; n 1⁄4 5; 55% purity; Lutalin, BASF Corp.), or 1% CLA (HIGH; n 1⁄4 6) top-dressed daily. Horses were fed individually every 12 h and offered 1% BW daily (as-fed) coastal bermudagrass (Cynodon dactylon) hay. This study was separated into 2 phases: phase 1 (d 0 to d 41) determined incorporation of CLA into plasma and synovial fluid; phase 2 (d 42 to d 56) evaluated potential of CLA to mitigate intraarticular inflammation and alter cartilage metabolism stimulated by LPS. Beginning at d 0, blood samples were collected each week, and synovial fluid samples were collected every 2 weeks to determine fatty acid concentrations. On d 42, carpal joints within each horse were randomly assigned to receive intra-articular injections of 0.5 ng LPS derived from Escherichia coli 055:B5 or sterile lactated Ringer's solution as contralateral control. Synovial fluid samples were obtained at pre-injection h 0 and 6, 12, 24, 168 and 336 h post-injection, and analyzed for prostaglandin E2 (PGE2), carboxypeptide of type II collagen (CPII), and collagenase cleavage neopeptide (C2C) by ELISAs. Data were analyzed using PROC MIXED procedure of SAS. Isomers of CLA were detectable in plasma by d 14, and synovial fluid by d 28. HIGH horses had greatest plasma CLA concentrations (P < 0.01), and CON horses had undetectable levels of CLA. Plasma arachidonic acid tended to be lower (P < 0.06) in HIGH horses than LOW and CON. Post LPS injection, synovial PGE2 was not affected by dietary treatment (P 1⁄4 0.15). Synovial C2C, however, was lower in HIGH horses than LOW (P 1⁄4 0.05), and synovial CPII tended to be higher in LOW horses compared with CON (P 1⁄4 0.10). In conclusion, dietary CLA reached circulating levels in plasma and synovial fluid before LPS challenge. Although CLA did not influence inflammation, as indicated by PGE2, there was a reduction in cartilage degradation and an increase in cartilage regeneration.