Interactive Effects of Dietary Fiber and Lipid Types Modulate the Predicted Production and Absorption of Cecal and Colorectal Short-Chain Fatty Acids in Growing Pigs.

BACKGROUND: High-fiber diets are supplemented with lipids to meet the required energy content, but data on the interactions between dietary fiber (DF) and lipid types on gastrointestinal fermentation in pigs are scant. OBJECTIVES: This study aimed to use a combination of in vivo and in vitro fermentation methodologies to determine the interactive effects of DF and lipid types on short-chain fatty acid (SCFA) production and absorption and organic matter (OM) fermentability in the cecum and colorectal tract of pigs. METHODS: Eight ileal- and cecal-cannulated Yorkshire barrows were fed either pectin- or cellulose-containing diets that were supplemented with either corn oil or beef tallow in 2 independent Youden squares with a 2 × 2 factorial arrangement of treatments (n = 6). Ileal and cecal digesta were collected, freeze-dried, and fermented using inoculum from fresh cecal digesta and feces, respectively, to determine individual SCFA production and absorption and fermentability of OM. RESULTS: Interactions (P < 0.001) between DF and lipid types were observed in which the addition of beef tallow decreased the quantity of cecal and colorectal acetic acid production and cecal acetic absorption, cecal butyric production, predicted cecal OM fermentability, and predicted colorectal propionic acid in pectin diets, but the effects were not observed for cellulose diets. The addition of beef tallow increased (P < 0.001) the production of cecal butyric and propionic acids during in vitro fermentation in cellulose diets and apparent total tract digestibility (ATTD) of OM in pectin diets. CONCLUSIONS: The interactions between DF and lipids on gastrointestinal fermentation largely depend on the degree of saturation of fatty acids in dietary lipids. The addition of beef tallow selectively decreased the production and absorption of individual SCFAs in pectin and cellulose diets but increased cecal butyric and propionic acid production in cellulose diets and the ATTD of OM in pectin diets.

Flaxseed meal and oat hulls supplementation: impact on dietary fiber digestibility, and flows of fatty acids and bile acids in growing pigs.

The present study was conducted to determine the effects of adding flaxseed meal (FM) or oat hulls (OHs) in pigs' diets on digestibility of dietary fiber (DF) and fatty acids (FAs), and gastrointestinal flows of FA and bile acids (BAs). Twelve Genesus [(Duroc ♂ × Yorkshire-Landrace ♀)] cannulated barrows (initial BW: 35.1 ± 0.44 kg) were individually housed and offered diets in a two-period cross-over design (n = 8). In each period, four pigs were assigned to one of the three corn-soybean meal-based diets without (control), or with FM or OHs. Soybean oil was added in each diet to give an FA content of 4.56%, 6.02%, and 6.05 % in the control, FM, and OH diets, respectively. Feces and ileal digesta contents were collected to determine apparent ileal (AID), total tract (ATTD) digestibility of dietary components and flows of FA and BA. Pigs fed the control diet had greater (P < 0.05) AID of SFA and insoluble DF and ATTD of SFA than pigs offered the OH and FM diets. The AID of total FA and MUFA in FM diet-fed pigs was lower (P = 0.02) compared to those fed the control and OH diets. The ATTD of CP, NDF, insoluble and total DF was lower (P < 0.05) in pigs fed the OH diet than in pigs that consumed the control and FM diets. In the terminal ileum, pigs fed OH and FM diets excreted more (P < 0.05) primary BA and all secondary BA (except lithocholic acid) compared to control diet-fed pigs. The intestinal flows of lithocholic acid in pigs fed the FM diet were higher (P < 0.05) than in pigs offered the control diet. Pigs fed FM and OH diets excreted more (P = 0.001) fecal ursodeoxycholic and total BAs compared to pigs that consumed the control diet. The ileal flows of eicosapentaenoic and erucic acids in pigs fed the FM and OH diets were greater (P < 0.05) than in pigs fed the control diet. The flow of all SFA, and palmitoleic, palmitelaidic, oleic, nervonic, linoleic, eicosapentaenoic, erucic, docosatetraenoic and docosapentaenoic acids in feces were greater (P < 0.05) in OH diet-fed pigs compared to pigs fed other diets. In conclusion, addition of FM and OHs in pig diets reduced FA digestibility, increased gastrointestinal flows of FA and excretion of BA. Dietary supplementation with FM and OHs induces variable effects on digestibility of DF fractions and fecal flows of unsaturated FA. Future studies are needed to quantify the contribution of endogenous FA losses from the host to gastrointestinal flows of FA.

Flaxseed meal and oat hulls supplementation: impact on predicted production and absorption of volatile fatty acids and energy from hindgut fermentation in growing pigs.

A combination of in vivo (ileal cannulated pigs) and in vitro (fecal inoculum-based incubation) methodologies were used to predict the effects of dietary supplementation with soluble or insoluble dietary fiber on hindgut VFA production and absorption. Energy contribution from hindgut VFA and apparent ileal (AID) and total tract (ATTD) digestibility of energy and DM was also investigated. Twelve ileal cannulated Genesus barrows (initial BW: 35.1 ± 0.44 kg) were allocated to 1 of the 3 corn-soybean meal-based diets without (control), or with flaxseed meal (FM) or oat hulls (OH) in a 2-period cross-over design. Flaxseed meal and oat hulls were used as sources of soluble and insoluble fiber, respectively. In each period, 4 pigs were offered 1 of the 3 diets, for 12 d followed by fecal (day 13 and 14) and ileal digesta collection (day 15 and 16) (n = 8). Ileal digesta were collected, freeze-dried, and subjected to in vitro fermentation using fecal inoculum, to predict production and absorption of VFA and energy production, and digestibility of DM and energy. The quantity of acetic, propionic, butyric, and valeric acids produced by in vitro fermentation was higher (P < 0.05) for the diet containing flaxseed meal compared with the control and OH diets. The predicted quantity of VFA produced and absorbed in the hindgut was greater (P < 0.05) in pigs that consumed the FM diet than those fed the control or OH diet. Pigs fed the control diet had greater (P < 0.05) AID and ATTD of DM than pigs offered the OH or FM diet. The determined disappearance of DM was lower (P < 0.05) in pigs fed the control and OH diets than in pigs that consumed the FM diet. The quantity of digested energy in the upper gut was reduced (P < 0.05) more in pigs fed the OH diet than in pigs fed the FM diet. The consumption of the FM diet increased (P < 0.05) the quantity of digested energy, energy produced and absorbed from VFA in the hindgut, and the percentage contribution of VFA from fermentation to total tract digestible energy, compared with the control and OH diets. In conclusion, dietary supplementation with insoluble fiber from oat hulls reduced ileal digested energy more than soluble fiber from flaxseed meal. Addition of soluble fiber to pig diets increased the energy contribution from VFA produced by hindgut fermentation to the total tract digestible energy, compared with dietary addition of insoluble fiber.

Interactive effects of dietary fibre and lipid types modulate gastrointestinal flows and apparent digestibility of fatty acids in growing pigs.

A total of eight ileal and caecal cannulated Yorkshire barrows were used to determine the interactions of dietary fibre (DF) and lipid types on apparent digestibility of DM and fatty acids (FA) and FA flows in gastrointestinal segments. Pigs were offered four diets that contained either pectin or cellulose with or without beef tallow or maize oil in two Youden square designs (n 6). Each period lasted 15 d. Faeces, ileal and caecal contents were collected to determine apparent ileal digestibility (AID), apparent caecal digestibility and apparent total tract digestibility (ATTD) of dietary components. The interactions between DF and lipid types influenced (P <0·05) the digestibility of DM and FA flows. The addition of maize oil decreased (P <0·05) AID of DM in pectin diets, and the addition of beef tallow depressed (P <0·001) ATTD of DM in cellulose diets. Dietary supplementation with beef tallow decreased (P <0·05) the AID of FA in pectin-containing diets but had no effects in cellulose-containing diets. Dietary supplementation with beef tallow increased (P <0·05) AID of SFA and PUFA and the flow of ileal oleic, vaccenic, linolenic and eicosadienoic acids and reduced the flow of faecal lauric, docosatetraenoic and docosapentaenoic acids in pectin- and cellulose-containing diets. In conclusion, the interaction between DF type and lipid saturation modulates digestibility of DM and lipids and FA flows but differs for soluble and insoluble fibre sources, SFA and unsaturated fatty acids and varies in different gastrointestinal segments.

Barley ß-glucan increases fecal bile acid excretion and short chain fatty acid levels in mildly hypercholesterolemic individuals.

The cholesterol-lowering effect of barley ß-glucan has been proposed to be the result of a pleiotropic effect, which involves several biological mechanisms such as gut fermentation, inhibition of intestinal cholesterol absorption and increased bile acid excretion and its synthesis. However, one of the recent studies from our laboratory indicated that increased bile acid excretion and subsequent increase in its synthesis, but not the inhibition of cholesterol absorption or synthesis might be responsible for the cholesterol-lowering effect of barley ß-glucan. Accordingly, the primary objective of the present study was to investigate the concentration of bile acids (BA), neutral sterols (NS) and short chain fatty acids (SCFA) excreted through the feces by mildly hypercholesterolemic subjects who consumed diets containing barley ß-glucan with varying molecular weights (MW) and concentrations. In a controlled, four phase, crossover trial, 30 mildly hypercholesterolemic but otherwise healthy subjects were randomly assigned to receive breakfast containing 3 g high MW (HMW), 5 g low MW (LMW), 3 g LMW barley ß-glucan or a control diet for 5 weeks. The concentrations of BA, NS and SCFA in the feces were measured at the end of each treatment phase. Compared to the other treatment groups, 3 g day-1 HMW barley ß-glucan consumption resulted in increased lithocholic acid (LCA) excretion (P < 0.001) but not LMW ß-glucan, even at the high dose of 5 g day-1. Increased fermentability of fibre was also evident from a significant increase in fecal total SCFA concentrations in response to the 3 g HMW ß-glucan diet compared to the 3 g LMW barley ß-glucan and control diet (P = 0.0015). In summary, the current results validate our previous report on the role of fecal bile acid excretion in cholesterol lowering through the consumption of barley ß-glucan. In addition, increased SCFA concentrations indicate that an increase in ß-glucan molecular weight promotes hindgut fermentation, which might also be playing a role in attenuating cholesterol levels.