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Digestibility of Calcium Salt of Fatty Acids and Soybean Oil in the Equine
L. K. Fehlberg, J. M. Lattimer, C. I. Vahl, J. S. Drouillard, and T. L. Douthit
Calcium salts of fatty acids (CSFA) frequently are fed to ruminants, but efficacy for equines is unknown. This study compared a proprietary CSFA and soybean oil with respect to impact on apparent total tract nutrient digestion and cecal fermentation parameters in equines. Eight cecally cannulated Quarter Horses were used in a crossover design in which horses consumed a diet for 28 d consisting of 1.5% BW (as-fed) Smooth Bromegrass hay and 0.5% BW (as-fed) pelleted concentrate supplemented with either a proprietary CSFA or soybean oil (OIL). Fecal samples were collected over a 3-d period on d 30 to 33 and 63 to 66 and analyzed for apparent total tract digestibilities of DM, NDF, ADF, CP, ether extract, and GE using acid-detergent insoluble ash as an internal marker. Cecal digesta samples were obtained on d 29 and 62 at 0, 2, 4, 6, 8, 10, and 12 h following the morning meal and analyzed for pH, VFA, and long chain fatty acid (LCFA) concentrations. Serum was collected following a 16-h fast and analyzed for triglycerides and cholesterol. Apparent total tract digestibilities of DM, NDF, ADF, CP, ether extract, and GE were unaffected by lipid source (P > 0.10). Serum triglycerides tended to be greater in horses consuming CSFA compared to OIL (P = 0.10); however, serum cholesterol was not different (P = 0.45). Average cecal pH in all horses regardless of treatment decreased below baseline during h 2, 4, 6, and 8 (P < 0.01) then increased to a level similar to baseline. Cecal concentration of total VFA tended to be greater in horses consuming OIL compared to CSFA at h 2 (P = 0.07). Cecal acetate, propionate, butyrate concentrations, and acetate:propionate also increased above baseline during h 4, 6, and 8 (P < 0.001) and returned to baseline values at h 10 and 12 (P > 0.10). Cecal propionate concentrations were less at h 2 for horses fed CSFA compared to horses fed OIL (P = 0.03). A treatment by time interaction was detected for total cecal LCFA concentration (P < 0.01); LCFA concentration was greater at h 2 for horses consuming CSFA compared to horses fed OIL (P = 0.02). The proprietary CSFA can be added to equine diets to increase energy density without adversely affection digestion of DM, NDF, ADF, CP, ether extract, and GE when compared to digestion of nutrients in horses consuming soybean oil.