The Effect of Dietary Microalgae on AAEP Lameness Scores and Whole Blood Cytokine Gene Expression Following a LPS Challenge in Mature Horses

Joint inflammation in horses can lead to reduced performance and mobility while chronic joint inflammation can lead to permanent damage. In horses, an intra-articular injection of lipopolysaccharide (LPS) can be used to produce a model of moderate but transient joint inflammation. The objective of this study was to determine if daily supplementation with microalgae could alter the clinical assessment of physiological measures, lameness score and whole blood mRNA levels of cytokines following an intra-articular lipopolysaccharide challenge in mature, healthy horses. Mature, mixed sex Thoroughbred horses were assigned to one of two treatments (n=5 per treatment), basal diet (CON) or basal diet plus 190 g/hd/d of a DHA-rich microalgae (ALG). After 60d on diets, a localized inflammation was induced by injecting 1.0 ng of LPS diluted into lactated ringers solution (LRS) into the medial carpal joint of a randomly selected leg. Sampling occurred at 0h (pre-injection), 12h, 24h and 48h post injection. Cytokine mRNA levels in blood were measured using real-time PCR with b-actin as a housekeeping gene. At 0h, AAEP lameness scores did not differ between treatments. Respiration rate and body temperature were not different at any time point. Heart rate tended to be higher (P= 0.07) at 12h in CON horses than ALG horses. At 12h, AAEP lameness scores were higher (P< 0.05) in CON horses compared to ALG. At 24h and 48h, lameness scores did not differ. At 0h, mRNA levels of interleukin 1Β tended (P = 0.06) to be lower in ALG horses compared to CON (0.92-fold and 1.27-fold, respectively). At time 12h, mRNA levels of interleukin 1B were increased (P <0.05) in CON horses compared to ALG (1.71-fold and 1.2-fold, respectively). Interleukin 8 mRNA levels tended (P=0.06) to be higher in CON to ALG (2.50-fold and 1.62-fold, respectively). There were no differences in mRNA levels between treatments at 24h and 48h. These results suggest that high DHA dietary microalgae can mitigate increases in lameness scores, heart rate and cytokine gene expression in a model of an intra- articular LPS challenge in horses