In this study, the effects of dietary fibre and types of indigestible markers (IM) on the apparent total tract digestibility (ATTD) of gross energy (GE) and nutrients as well as IM recovery in diets fed to growing pigs were investigated. A total of 30 barrows (initial body weight 40.5 ± 1.4 kg) were allotted to five experimental diets, based on a completely randomised block design, with body weight as a blocking factor. The five diets comprised a corn-soya bean meal basal diet, and four diets in which sugar beet pulp (SBP) or defatted rice bran (DFRB) partly replaced 10% or 20% of corn, soya bean meal and soya bean oil in the basal diet. All diets were formulated to contain two types of IM, namely 0.5% chromic oxide (Cr) and 1.0% celite as the source of acid-insoluble ash (AIA). Animals were subjected to a 7-d adaptation period, and their faeces were collected over a 5-d period using the total faecal collection (TC) method. Results showed that the AIA method determined similar ATTD of GE and nutrients as the TC method. Values of dietary nutrients determined via AIA and TC methods were significantly higher than those obtained by Cr (p < 0.05). The ATTD of GE and nutrients linearly decreased with an increased inclusion level of SBP or DFRB (p < 0.01), whereas recoveries of AIA and Cr were not affected by the aforementioned inclusions. Results from the faecal analysis revealed that AIA recovery (90.5%) was significantly higher than that of Cr (84.9%, p < 0.05), while diets with DFRB (91.3%) had significantly greater IM recovery rates than those with SBP (84.4%, p < 0.05). In conclusion, the type of dietary fibre, rather than the level, significantly affects IM recovery. Notably, AIA should be preferred to Cr when using the IM method to determine ATTD of GE and nutrients for diets in growing pigs.
Keywords: Apparent total tract digestibility; celite; chromic oxide; dietary fibre; indigestible marker; pigs; recovery; total faecal collection.