Effects of β-Glucans and resistant starch on fermentation of recalcitrant fibers in growing pigs

Effects of the presence of β-glucans and resistant starch in diets on nutrient and fiber degradability of rapeseed meal [RSM] (Brassica napus) and Distillers Dried Grain with Solubles (DDGS) were tested in a 2 × 3 factorial arrangement. Two basal diets, containing either 500 g/kg RSM or DDGS and ~400 g/kg corn starch were formulated to meet or exceed nutrient requirements of growing pigs. Corn starch was partly replaced with the β-glucan-extract (β-GLUC; 60 g/kg w/w) or completely replaced with retrograded tapioca (RG; 400 g/kg w/w), resulting in 6 dietary treatments. A total of 10 crossbred barrows (initial body weight, 28 ± 1.4 kg (SD); Duroc × Large White/Landrace; Hypor, Inc., Regina, SK, Canada) were fed the 6 experimental diets. In total, 46 observations were obtained in 10 pigs over 7 periods in an incomplete 10 × 7 Youden square. Each of 7 sequential 14 days experimental periods consisted of a 9 days adaption to the diets followed by 2 days collection of feces, 2 days collection of ileal digesta for digestibility measurements, and 1 day collection of ileal digesta for the measurement of retention time. Pigs were weighed weekly during the experiment after consuming their morning meal. Feces were collected from 08.00 to 17.00 h using bags attached to rings glued around the anus. Bags were collected within 1 h after defecation and immediately frozen (-20 °C). Ileal digesta for digestibility measurements were collected from 08.00 to 17.00 h into plastic bags (10 cm in length and 4 cm in diameter). The bags were removed when filled approximately 70 % with digesta, or after a maximum of 1 h, and immediately frozen (-20 °C). For retention time measurements, on day 14 of each experimental collection, 3.4 g Cr as Cr2O3 (solid phase marker) and 3.4 g Co as Co (II)-EDTA (soluble phase marker) were mixed into the morning meal. Digesta were collected at 45, 90, 180, 270, 360, 540, and 720 min after feed consumption.