The effects of feed intake and fiber type on apparent ileal and total tract digestibility and hindgut disappearance of energy and nutrients in growing pigs

Two experiments were conducted to test the hypothesis that there are interactive effects of feed intake and fiber type on energy and nutrient digestibility in growing pigs. In Exp. 1, twelve barrows with an initial body weight (BW) of 34.0 kg (SD = 2.6) were allotted to a 2 × 3 factorial arrangements consisting of 2 daily feeding levels (9.0% and 4.5% × BW0.75) and 3 experimental diets in a replicated 6 × 4 incomplete Latin square design with 6 treatments and 4 periods. The experimental diets were a corn-soybean meal-based diet, a diet containing 30% sugar beet pulp (SBP, soluble dietary fiber 19.1% and insoluble dietary fiber 48.5%), and a diet containing 15% corn cobs (soluble dietary fiber 1.1% and insoluble dietary fiber 83.8%). Results indicated that there were no interactions between feed intake and fiber type on energy and nutrient digestibility. The reduction of feed intake increased (P < 0.05) digesta passage time and apparent total tract digestibility (ATTD) of energy, dry matter (DM), organic matter (OM), neutral detergent fiber (NDF), and acid detergent fiber (ADF) in pigs. The SBP diet had greater (P < 0.05) ATTD of energy, DM, OM, NDF, and ADF compared with the corn cob diet. The ingredient SBP also had greater (P < 0.01) ATTD of energy, DM, OM, crude protein, NDF, and ADF compared with corn cobs. In Exp. 2, ten ileal-cannulated barrows with an initial BW of 38.3 kg (SD = 5.4) were allotted to 5 treatment groups in a replicated 5 × 4 incomplete Latin square design with 5 treatments and 4 periods to obtain 8 observations for each treatment. A 1 + 2 × 2 factorial treatment arrangement consisted of a corn-soybean meal-based diet fed at 9.0% × BW0.75 per day and 2 main effects of feeding levels (9.0% and 4.5% × BW0.75) and fiber type (a 30% SBP diet and a 15% corn cob diet). The ATTD and hindgut disappearance of energy, DM, OM, NDF, and ADF in the SBP diet were greater (P < 0.05) compared with the corn cob diet. When calculated by difference for the digestibility of ingredients, the ATTD and hindgut disappearance of energy, NDF, and ADF in SBP was greater (P < 0.05) than those in corn cobs. Taken together, feed intake reduction resulted in increased fiber digestibility. The SBP rich in soluble dietary fiber had greater energy and fiber digestibility compared with corn cobs composed mostly of insoluble dietary fiber. No interaction existed between feed intake and fiber type in the digestibility of growing pigs.