Effect of dietary fibre source on total tract digestibility, caecum volatile fatty acids and digestive transit time in the weaned piglet

Effects of the use of 200 g of either wheat bran, sugar beet pulp, soya bean hulls or alfalfa meal per kilogram diet on the digestive process of the weaned piglet were studied on 24 Duroc x Landrace male piglets, weaned at 28 days of age. Piglets had an initial mean live weight of 7.92(+/-1.1) kg and were randomly distributed in six successive blocks of four animals. The total tract apparent digestibility (TTAD) was 0.872, 0.887, 0.815 and 0.824 for energy and 0.847, 0.833, 0.665 and 0.795 for nitrogen for the wheat bran, sugar beet pulp, soya bean hulls and alfalfa meal diet, respectively (P < 0.01). The TTAD values for NDF were 0.615, 0.861, 0.721 and 0.593, and for ADF were 0.390, 0.779, 0.708 and 0.457 in diets based on wheat bran, sugar beet pulp, soya bean hulls and alfalfa meal, respectively (P < 0.01). The level of volatile fatty acids (VFAs) in the caecum contents changed from 3.80 to 4.96 mg g(-1) when sugar beet pulp replaced soya bean hulls, respectively, the later producing a higher proportion of acetic acid (P < 0.05). The average molar proportions were 0.635, 0.245 and 0.10 for acetic, propionic and butyric acid, respectively. Soya bean hulls in the diet increased the level of total VFA by 15 or 30% when compared with the wheat bran or with the sugar beet pulp and the alfalfa meal, respectively (P < 0.05). For a constant nitrogen intake, the diet containing soya bean hulls supported the lowest nitrogen retention. The mean retention time was 51.5, 49.9, 56.9 and 37.7 h for diets based on wheat bran, sugar beet pulp, soya bean hulls and alfalfa meal, respectively (P < 0.01). In contrast to alfalfa meal, the soya bean hulls reduced the chromium excretion rate by 40% and delayed the inflexion point of the excretion curve by 11 h, and consequently the digestive transit time. In conclusion, sugar beet pulp has the highest degradation rate of NDF and ADF fractions. The inclusion of soya bean hulls leads to a decrease in the energy and nitrogen digestibility of the weaning diet. Finally, alfalfa meal was the most effective fibre source to regulate the digestive transit time. (C) 2000 Elsevier Science B.V. All rights reserved.