Feeding and microbial disorders in horses: Part 3—Effects of three hay:grain ratios on microbial profile and activities

Cecal and colonic fluid contents were collected from three ponies and analyzed to determine the effects of three hay:barley ratios on their microbial and biochemical characteristics. Three diets based on chopped meadow hay and rolled barley were tested in a 3×3 Latin square experiment: 100% hay (100:0, 114gDM/KgBW^0.75/day), 70% hay-30% barley (70:30, 69gDM/KgBW^0.75/day) and 50% hay-50% barley (50:50, 58gDM/KgBW^0.75/day). Enumeration of total anaerobic and aero-anaerobic bacteria, lactate-utilizing and cellulolytic bacteria, lactobacilli and streptococci, as well as pH, lactate and VFA concentrations, were determined after 14 days adaptation to the new diet. In the large intestine, the concentrations of total bacteria were higher with the diets containing barley than with the hay diet, whereas cellulolytic bacteria were depressed with the concentrate diets. As the proportion of barley increased, concentration of lactate-utilizing bacteria, lactobacilli and streptococci increased in the colon while it did not interfere significantly on these populations in the cecum. These changes of the microflora were associated with a significant decrease in intestinal pH and (acetate+butyrate)/propionate] ratio, and a numerical increase of lactate concentration.