Quantification of short-chain fatty acids and energy production from hindgut fermentation in cannulated pigs fed graded levels of wheat bran.

Abstract

This study investigated the amount of energy available to growing pigs from fermentation of dietary fiber in the hindgut. Eighteen growing barrows, fitted with a simple T-shaped cannula at the terminal ileum, were allocated to 3 experimental diets in a completely randomized design. The 3 diets were a standard-fiber diet (SFD), which contained 75.1 g NDF/kg diet; a medium-fiber diet (MFD) of 105.7 g NDF/kg diet; and a high-fiber diet (HFD), which contained 146.9 g NDF/kg diet. Each diet had 6 replicate pigs. After a 5-d period of adjustment of the pigs to the cage environment, feces were collected on d 6 and 7 and ileal digesta on d 8 and 9 and subsequently freeze-dried. Fecal slurry from a pig was used to inoculate the ileal digesta from the same pig. The amount of energy available was calculated from the amount of short-chain fatty acids (SCFA) produced from a 48-h in vitro fermentation of the ileal digesta. Increasing NDF enhanced ( < 0.01) the ileal DM flow and DM in feces. The energy available in the foregut was reduced ( < 0.05) from 3,360 to 2,974 kcal/kg feed DM and increased ( < 0.01) from 619 to 1,009 kcal/kg feed DM produced in the hindgut with increasing dietary NDF. The amount of SCFA increased ( < 0.01) with higher dietary NDF. Acetic acid was highest ( < 0.01) in the HFD whereas propionic and valeric acids were highest ( < 0.05) in the SFD. The amount of butyric acid was not affected by diet. The amount of energy contributed from SCFA fermentation to total tract digestible energy increased ( < 0.01) from 10.7 to 24.2% as dietary NDF level increased from 75 to 147 g/kg feed. The results of the study showed that increasing level of dietary NDF resulted in reduced energy digestibility in the foregut of growing pigs with a corresponding increase in the amount of energy from microbial fermentation in the hindgut.