The Effect of Dietary Fibre Level and Microbial Activity in the Digestive Tract on Fat Metabolism in Rats and Pigs

Abstract

Castrated conventional male Landrace pigs [12] and 12 SPF [specific pathogenic-free] male Wistar rats with an initial live weight of 22-26 kg and 60-70 g, respectively, were allocated at random to 4 diets. The diets consisted of barley, soybean meal, and meat and bone meal without (A and B) or with (C and D) the addition of grass meal to provide both a low level (49 g/kg) and a high level (105 g/kg) of crude fiber. Nebacitin was added to diets B and D at a level of 7 g/kg in order to reduce the microflora content in the gut. The Nebacitin treatment reduced the concentration of total lipids and phospholipids in fecal material significantly, whereas sterols increased significantly. All criteria were lower in fecal material of pigs fed high crude fiber levels compared to low crude fiber levels. Hydrogenation of unsaturated fatty acids, especially of linoleic acid, could be reduced markedly by Nebacitin. Proportions by molarity of short-chain fatty acids were also significantly affected by the microbial activity in the digestive tract. Butyric acid was almost eliminated in hind-gut materials when Nebacitin was added to the diets. The same was also the case with valeric acid. In general all but acetic and propionic acids were lower on the low level of microflora. Acetic acid increased significantly while propionic acid was hardly affected from the microbial activity. Dietary crude fiber level had not much effect on the level of short-chain fatty acids in digesta from the hind-gut of rats. The same was also the case in blood serum, while the Nebacitin-treated rats had a much lower level of acetic acid in blood serum.