Effect of graded levels of fiber from alfalfa meal on intestinal nutrient and energy flow, and hindgut fermentation in growing pigs1

Abstract

The objective of this experiment was to determine the effects of fiber level from alfalfa meal and collection period on intestinal nutrient and energy flow, and hindgut fermentation in growing pigs. Twenty-four pigs (initial BW = 21.4 ± 1.5 kg) were prepared by T-cannula insertion into the distal ileum and allotted to 4 treatments. The pigs were provided a corn-soybean meal control diet or a diet in which corn and soybean meal were partly replaced by 5%, 10%, or 20% alfalfa meal to give the graded levels of dietary fiber during two 10-d collection periods. The BW of pigs at the start of periods 1 and 2 were 32.2 ± 2.4 and 37.7 ± 4.2 kg, respectively. The final BW at the end of period 2 was 46.8 ± 4.0 kg. The apparent ileal digestibility (AID) and apparent total tract digestibility (ATTD) of nutrients and energy were measured. The VFA concentration was also determined in the ileal and fecal samples. Nutrient digestibility was not affected by inclusion of 5% alfalfa meal in the diet. The AID, ATTD, and hindgut fermentation of DM, carbohydrates (CHO), and GE decreased (linear, P < 0.05) as the level of alfalfa meal in the diet increased. The intestinal flow of DM, CHO, ADF, and GE increased (linear, P < 0.05) by increasing the level of dietary alfalfa. The pH in ileal digesta and concentration of acetate, propionate, and total VFA in the feces increased (linear, P < 0.01) as the level of alfalfa meal in the diet increased. From experiment period 1 to 2, ATTD and hindgut fermentation of CHO decreased (P < 0.01), whereas concentrations of propionate, valerate, and total VFA in ileal samples increased (P < 0.05). A multiple linear regression analysis, taking into account both soluble dietary fiber and insoluble dietary fiber intake, explained the variation (P < 0.01) in total tract flow of NDF (93%), ADF (84%), GE (73%), DM (71%), and CHO (62%). In conclusion, the diet containing 5% of alfalfa meal did not affect nutrient and energy digestion. Intestinal flow of CHO decreased during the 10-d collection period. The VFA concentration increased with fiber level and 10-d exposure to the experimental diets. Soluble and insoluble fibers from alfalfa meal have differential roles in nutrient digestion, which may help explain the variation observed in the intestinal flow of nutrients.