Intrinsic ability of the faecal microbial flora to ferment dietary fibre at different growth stages of pigs

Apparent in vivo digestibility of a low dietary fibre (DF) diet and a high DF (from maize bran) diet was measured in 40-kg BW growing pigs (G), 8 1-kg BW finishing pigs (F) and 23 1-kg BW adult sows (A). Faecal inocula were collected at each physiological stage and for each diet and used to study the in vitro microbial degradation of fibre from sugar beet pulp and maize bran. The apparent in vivo digestibility of dietary energy and most nutrients increased with BW of pigs (P < 0.01) but the effect was greater when animals received the high DF diet (P < 0.01). The improved digestibility of the fibre-rich diet was mainly related to increased digestibility of fibre of maize bran: 35, 51 and 78% in G, F and A pigs, respectively. In vitro fermentation of maize bran fibre was lower than that of sugar beet fibre; however, it was not affected by the DF content of the diet or by the BW of pigs. Moreover, it was decreased with the inoculum from adult sows fed the fibre-rich diet (P < 0.01). These results indicate that the greater ability of heavy pigs or adult sows to digest DF is not due to an increased intrinsic ability of the microbial flora to degrade DF. (C) 2002 Elsevier Science B.V. All rights reserved.