s / Journal of Equine Veterinary Science 31 (2011) 230-356 270 Nutrition: Oral Presentations I Synovial Prostaglandin E2 Concentrations in Horses Fed Long Chain Polyunsaturated Fatty Acids: An Inquiry Study T. Ross, T.Hess,D.Hansen, T. Engle,N. Schauermann, and J. Rexford Colorado State University, Fort Collins, CO USA Introduction: Elevating n-3 fatty acids in mammalian diets may decrease inflammatory processes in the joint.1 One hypothesized mechanism is the potential of n-3 long chain polyunsaturated fatty acids (LCPUFA) to reduce the production of potent inflammatory eicosanoids, primarily prostaglandin E2 (PGE2). 2 Little to no information exists regarding oral n-3 supplementation and effects on inflammatory markers common in the equine joint. Therefore, mature horses were fed dietary n-3 LCPUFA for ninety (90) days to determine if oral supplementation alters synovial concentrations of PGE2. Materials and Methods: Twenty-onematuremixed breedmares with no history of joint disease and free of lameness were blocked by age, weight and body condition score and randomly assigned into one of three dietary treatment groups. Basal diet consisted of alfalfa/bromegrass mixed hay with the addition of rolled barley grain. Amount of barley varied with treatment groups to keep diets isocaloric and isonitrogenous. Group 1 (FISH) received 69 mg/kg BW of the n-3 polyunsaturated fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) via a commercial fish oil supplement (Magnitude ; JBS United, Sheridan, IN) daily; Group 2 (FLAX) received 68.6 mg/kg BW of the n-3 polyunsaturated fatty acid alpha linolenic acid (ALA) via a flaxseed supplement (Nutra-Flax) daily and Group 3 (CONT) did not receive an oral n-3 supplement. Total diet composition of n-3 LCPUFA were approximately 143.5 mg/kg BW (FISH), 142.5 mg/kg BW (FLAX) and 78.7 mg/kg BW (CONT), respectively. On day 90, approximately 3 ml of synovial fluid was extracted from a random carpal joint of each horse and immediately placed into a 5 ml EDTA tube. Samples were processed and stored at -20 C until laboratory analysis was conducted. Prostaglandin E2 levels were determined using a two step process. In short, synovial fluid samples were first subjected to solid-phase extraction procedures using C2 ethyl minicolums(SampliQ ; Agilent Technologies, Wilmington, DE). Samples were then evaluated in triplicate using a commercially available PGE2 ELISA kit (Assay Designs; Ann Arbor, MI). Prostaglandin E2 levels were expressed in pg/ml. Data were analyzed using statistical software (SAS; Cary, NC) by use of one-way analysis of variance with significant differences (P < .05) being further evaluated using Fisher's LSD test. Results and Discussion: Synovial PGE2 levels at day 90 were within concentration ranges reported previously for values obtained from healthy equine joints.3 Though not significant, therewas a trend (P1⁄4 .075) for PGE2 concentrations to be lower in FISH group (21.261 +/4.01 pg/ml) compared to CONT group (32.2302 +/4.01 pg/ml). A ninety (90) day supplementation of the n-3 fatty acid ALA resulted in no difference in PGE2 concentrations (28.202 +/4.9 pg/ml) when compared to FISH (P1⁄4 .2932) or CONT (P 1⁄4 .5360) horses. In a companion inquiry, synovial fluid fatty acid levels for EPA and DHA were significantly higher in the FISH group compared to either CONT or FLAX groups.4 Though levels did not differ between treatments, the FISH group expressed the lowest levels of PGE2 in the current study; likely due to having higher concentrations of EPA and DHA in the joint. Prostaglandin E2 concentrations have been reported to be higher in joints of horses with existing osteoarthritis compared to levels in normal, healthy joints.3 Additionally, synovial fluid PGE2 levels have been positively correlated to degree of lameness and joint effusion in dogs,5 indicating usefulness as an indicator of joint inflammation and as a therapeutic target. Osteoarthritic horses receiving oral n-3 fatty acid supplementation for 90 days had lower plasma PGE2 and synovial white blood cell concentrations when compared to arthritic horses receiving no n-3 fatty acid supplementation,6 demonstrating a potential benefit of oral n-3 fatty acids for reducing severity of pain and inflammation. The lack of difference in synovial fluid PGE2 concentrations in the current study may be due to all horses being healthy and free of existing joint inflammation or disease. Conclusion: Data presented here indicate a possible inhibition of inflammatory eicosanoid prostaglandin E2 production by oral supplementation of the polyunsaturated fatty acids EPA and DHA. Further research is needed to determine if oral n-3 LCPUFA supplementation can be therapeutically advantageous in horses experiencing joint inflammation. Total and Water-soluble Phosphorus Excretion in Horses Consuming All-Forage Diets L.K. Warren, S. Dilling, J. Kivipelto, J. Bobel, and J. Eckert University of Florida, Gainesville, FL USA Introduction: Disposal of animal manure is under increasing scrutiny because of growing public concern over the long-term effects on phosphorus (P) accumulation in soils and its contribution to water quality degradation and eutrophication. When manure is applied to pastures or deposited by the grazing animal, soils will retain most of the P applied in excess of plant uptake. Despite the generally high adsorption capacity of most soils, P leaching can occur and P losses to runoff or surface erosion can be high. Potential P loss is not only related to the amount of P excreted in manure, but also how easily the manure P is dissolved in storm water and subject to runoff loss. Specifically, the chemical forms of P and their relative proportions inmanure influence runoff risk. Sharpley and Moyer [1] found a strong correlation betweenwater soluble P in livestock and poultry manures and the amount of P leached from soil following simulated rainfall events. Thus the soluble P fraction in manure is thought to pose the greatest environmental risk. Water soluble P has been shown to be highly correlated with daily P intake in livestock and poultry.[2] Although total P excretion has been positively correlated with P intake in horses,[3] the soluble P content of horse manure, as well as the effect of diet on fractional P excretion in horses is unknown. This study was undertaken to evaluate total and soluble P excretion in horses consuming an allforage diet. Materials and Methods: Six mature horses (mean SE, 530 14 kg) were fed 3 different hays in a 3 X 3 Latin square design. In