Effect of Concentrate form on blood and gastric fluid variables in ponies

Summary Eight ponies were used in a two-period, crossover design experiment to determine if the physical form of a concentrate feed affected selected gastric fluid and blood variables. Each pony had been surgically fitted with a gastric cannula 2 years prior to the study. In each 29-day period, four ponies received hay and a pelleted concentrate and four ponies received hay and a textured (sweet feed) concentrate. The concentrate portions of the diets were identical except for physical form and contained 57.5% corn, 25% oat, 8.5% soybean meal, 7% molasses and 2% minerals and vitamins. On day 15 of each period, the ponies received a concentrate meal (.4% of body weight) and blood and gastric fluid samples were obtained for 9 h after feeding. Feeding a concentrate meal resulted in increased plasma glucose, serum insulin, gastric fluid glucose and gastric fluid L-lactate concentrations. The pH of gastric fluids before feeding ranged from 1.4 to 8.36, but gastric fluid pH was at least 5.0 within 30 min of eating in all ponies. Few effects of concentrate form were observed, but plasma glucose concentrations at 150 and 180 min after feeding were higher (P