Influence of Dietary Fiber on the Performance and Cellulase Activity of Growing-Finishing Swine1

Number of cellulolytic bacteria and their cellulase activity were determined from fecal samples of eight pairs of littermate pigs representing four litters (26 to 32 kg) fed a low or high fiber diet ad libitum (0 or 35% alfalfa meal, respectively) over a 70-d period. Fecal samples were obtained from all pigs on d 0, 5, 11, 18, 32, 53 and a final sample between d 67 to 70. Cecum and colon samples were obtained at slaughter. Growth and carcass data were also obtained during the study. Pigs fed the high fiber diet gained 17.3% less, had increased feed to gain ratio and less carcass weight at slaughter than those fed the low fiber diet (P less than .05). Overall, a larger number of cellulolytic bacteria (P less than .05) were found in the fecal samples from pigs fed the high fiber diet. The overall mean cellulolytic activity (mg glucose released X g dry weight fecal sample-1 X 30 min-1) was 27.7 compared with 33.8 (P less than .05) for the pigs fed the low and high fiber diet, respectively. A lower concentration of organic acids (P less than .05) was present in the fecal samples of the high fiber pigs. The overall mean acetate to propionate ratio was 1.92 and 2.48 (P less than .01), and ammonia-N was 2.27 and .98 mg/g dry weight (P less than .01) for the low and high fiber diet pigs, respectively. These data indicated that a 35% alfalfa meal diet significantly affects intestinal bacterial metabolism and number and activity of the cellulolytic population, along with performance and carcass characteristics.