Energy concentrations and nutrient digestibility of high-fiber ingredients for pigs based on in vitro and in vivo assays

Abstract

The objective of the present study was to determine energy concentrations and nutrient digestibility of high-fiber ingredients for pigs using in vitro and in vivo assays. In experiment 1, in vitro ileal and total tract disappearance of nutrients in soybean hulls, corn gluten feed, wheat bran, rice bran, and cashew nut testa were determined. Two-step and 3-step in vitro procedures were used to simulate the digestion of nutrients in the gastrointestinal tract of pigs. The coefficient of in vitro ileal disappearance of dry matter (DM) in rice bran was the greatest (P < 0.05) among the test ingredients followed by wheat bran, corn gluten feed, cashew nut testa, and soybean hulls. The coefficient of in vitro total tract disappearance of DM and organic matter in rice bran was also the greatest (P < 0.05) among the test ingredients followed by wheat bran, cashew nut testa, corn gluten feed, and soybean hulls. In experiment 2, in vivo energy values and nutrient digestibility of the same ingredients used in experiment 1 were determined. Twelve barrows with an initial body weight of 57.5 kg (standard deviation = 5.7) were assigned to 6 experimental diets in a replicated 6 × 4 incomplete Latin square design. A basal diet consisted of 750 g/kg corn and 227 g/kg soybean meal (SBM) as the sole energy sources. Four experimental diets were prepared by replacing 400 g/kg of corn and SBM with soybean hulls, corn gluten feed, wheat bran, or rice bran. An additional diet was prepared by replacing 100 g/kg of corn and SBM with cashew nut testa. Each period consisted of a 4-day adaptation period and a 4-day collection period. On an as-fed basis, digestible energy and metabolizable energy concentrations in soybean hulls (2198 and 2242 kcal/kg), corn gluten feed (2317 and 2227 kcal/kg), and wheat bran (2751 and 2679 kcal/kg) were less (P < 0.05) than those in rice bran (3503 and 3459 kcal/kg), but those were greater (P < 0.05) than those in cashew nut testa (352 and 519 kcal/kg). The coefficient of apparent total tract digestibility of DM in wheat bran was greater (P < 0.05) than that in corn gluten feed and cashew nut testa. In conclusion, energy values and nutrient digestibility in rice bran were the greatest among the high-fiber ingredients, whereas cashew nut testa had the lowest values based on the present in vitro and in vivo experiments. In vitro procedures can be a potential alternative method for determining energy digestibility of ingredients for pigs.