Effect of increasing dietary fermentable fiber on diet nutrient digestibility and estimation of endogenous phosphorus losses in growing pigs.

Fermentable fiber may increase endogenous losses of phosphorus (EPL) and amino acids (AA), thereby reducing apparent nutrient digestibility. Acacia gum with medium-to-high fermentability and low viscosity was increasingly included in diets to investigate its effect on apparent ileal digestibility (AID) and apparent total tract digestibility (ATTD) of nutrients, gross energy (GE), and standardized total tract digestibility (STTD) of P in growing pigs. A control diet (49% cornstarch; 18% bovine plasma protein) was formulated to measure basal EPL. Three additional diets were formulated to include 2.5%, 5.0%, or 7.5% acacia gum at the expense of cornstarch. Diets contained 16.1% to 17.4% CP and 0.31% to 0.33% total P (DM-basis). The four diets were fed to eight ileal-cannulated barrows (initial BW, 54.6 kg) for four 9 d periods in a double 4 × 4 Latin square. Apparent hindgut fermentation (AHF) was calculated as ATTD minus AID. Feeding increasing acacia gum quadratically affected (P < 0.05) AID of DM, GE, linearly decreased (P < 0.05) ATTD of DM, crude protein (CP), GE, digestible (DE) and predicted net energy (NE) value of diets, and linearly increased (P < 0.001) AHF of DM and GE. Increasing acacia gum did not affect AID and standardized ileal digestibility (SID) of CP and AA. Basal EPL was 377 mg/kg DM intake (DMI) and increasing acacia gum linearly increased (P < 0.05) total tract EPL. Increasing acacia gum linearly decreased (P < 0.05) diet ATTD of P, and STTD of P based on either the calculated EPL or NRC (2012) recommended value (190 mg P/kg DMI). Increasing acacia gum did not affect AID and ATTD of Ca of diets. In conclusion, feeding increasing dietary fermentable, low-viscous acacia gum decreased diet AID and ATTD of DM and GE, but did not affect AID or SID of CP and AA. Increasing acacia gum decreased ATTD of P, which might have been due to increased specific endogenous losses of P in the total tract of growing pigs.

Fermentable fiber may increase endogenous losses of phosphorus (EPL) and amino acids (AA), thereby reducing nutrient digestibility. This study assessed effects of feeding increasing acacia gum with medium-to-high fermentability and low viscosity. Eight barrows cannulated at the terminal ileum were fed a control diet to measure basal endogenous P losses and three diets including 2.5%, 5.0%, or 7.5% acacia gum. Increasing acacia gum quadratically decreased diet ileal digestibility of dry matter (DM), gross energy (GE), linearly decreased diet total tract digestibility of DM, crude protein (CP), GE, and linearly increased hindgut fermentation of DM and GE. Increasing acacia gum linearly increased total tract endogenous P losses. Increasing acacia gum linearly decreased diet total tract digestibility of P, and standardized total tract digestibility of P calculated based on the calculated endogenous P losses or table values (NRC, 2012; 190 mg P/kg DMI). In conclusion, increasing dietary fermentable, low-viscous acacia gum decreased diet ileal and total tract digestibility of DM and GE, but did not affect ileal digestibility of CP and most AA. Increasing acacia gum inclusion reduced total tract digestibility of P, which might have been due to increased specific endogenous losses of P in the total tract of growing pigs.

Dietary benzoic acid and supplemental enzymes alter fiber-fermenting taxa and metabolites in the cecum of weaned pigs.

Inclusion of enzymes and organic acids in pig diets is an important strategy supporting decreased antibiotic usage in pork production. However, limited knowledge exists about how these additives impact intestinal microbes and their metabolites. To examine the effects of benzoic acid and enzymes on gut microbiota and metabolome, 160 pigs were assigned to one of four diets 7 days after weaning: a control diet or the addition of 0.5% benzoic acid, 0.045% dietary enzymes (phytase, ß-glucanase, xylanase, and α-amylase), or both and fed ad libitum for 21 to 22 d. Individual growth performance and group diarrhea incidence data were collected throughout the experimental period. A decrease of 20% in pen-level diarrhea incidence from days 8 to 14 in pigs-fed both benzoic acid and enzymes compared to the control diet (P = 0.047). Cecal digesta samples were collected at the end of the experimental period from 40 piglets (n = 10 per group) and evaluated for differences using 16S rRNA sequencing and two-dimensional gas chromatography and time-of-flight mass spectrometry (GCxGC-TOFMS). Analysis of cecal microbiota diversity revealed that benzoic acid altered microbiota composition (Unweighted Unifrac, P = 0.047, r2 = 0.07) and decreased α-diversity (Shannon, P = 0.041; Faith's Phylogenetic Diversity, P = 0.041). Dietary enzymes increased fiber-fermenting bacterial taxa such as Prevotellaceae. Two-step feature selection identified 17 cecal metabolites that differed among diets, including increased microbial cross-feeding product 1,2-propanediol in pigs-fed benzoic acid-containing diets. In conclusion, dietary benzoic acid and enzymes affected the gut microbiota and metabolome of weaned pigs and may support the health and resolution of postweaning diarrhea.

Feeding weaned pigs diets containing benzoic acid or supplemental enzymes for 21 d after weaning changed the gut microbiota and metabolome. Benzoic acid increased feed intake, weight gain, and the presence of 1,2-propanediol in cecal digesta, which is an important microbial cross-feeding product. Dietary enzymes altered microbiota composition, increasing the presence of fiber-fermenting microbes including Prevotellaceae. Pigs fed a combination of both benzoic acid and enzymes showed improved resolution of postweaning diarrhea. These differences demonstrate the role of these feed additives in the establishment of gut microbes and metabolic pathways for the degradation of complex dietary components in the weaned pig. This study provides new information about alterations in microbial function and community composition using microbiota sequencing and metabolomic analysis.

Cereal grain fiber composition modifies phosphorus digestibility in grower pigs.

Increased fermentable carbohydrates (e.g., ß-glucan, amylose) may increase endogenous losses including for P, and thereby reduce apparent total tract digestibility (ATTD) of P. The present study assessed effects of barley cultivars varying in fermentable starch and fiber on apparent ileal digestibility (AID) and ATTD of P, myo-inositol 1,2,3,4,5,6-hexakis (dihydrogen phosphate; InsP6) and Ca, and standardized total tract digestibility (STTD) of P and the presence of lower inositol phosphates (InsP) compared to wheat. In a 6 (period) × 5 (diet) Youden square, seven ileal-cannulated barrows (initial BW, 27.7 kg) were fed diets containing 80% of one of five cereal grains differing in amylose, ß-glucan, and fiber content: 1) high-fermentable, high-ß-glucan, hull-less barley (HFB); 2) high-fermentable, high-amylose, hull-less barley (HFA); 3) moderate-fermentable, hull-less barley (MFB); 4) low-fermentable, hulled barley (LFB); and 5) low-fermentable, Canadian Western Red Spring wheat (LFW). On dry matter (DM) basis, cereal grains contained between 0.32% to 0.53% total P and 0.24% to 0.50% InsP6-P. The InsP6-2-P was calculated as the sum of all detected InsP-P (InsP6-P to InsP2-P) in the sample. The P release of degraded InsP-P was calculated by using the following equation: sum InsP6-2-Pdiet (g/kg DM) × (AID or ATTD sum InsP6-2-P (%)/ 100). Data were analyzed using a mixed model with diet as fixed effect, and pig and period as random effects. On DM basis, diets contained 41.4% to 50.6% starch, 0.88% to 8.54% ß-glucan, 0.81% to 0.89% total P, and 0.19% to 0.35% InsP6-P. The MFB, LFB, and LFW had greater (P < 0.05) diet AID of P than HFB and HFA, and MFB had greater (P < 0.05) diet ATTD and STTD of P than HFB. The ATTD of InsP6-P was greater (P < 0.05) for HFB than LFB and the ATTD of the sum InsP6-2-P was greater (P < 0.05) for HFB and HFA than LFB. Total tract P release was greater (P < 0.001) for HFB, HFA, and LFW than MFB and LFB. The LFW had greater (P < 0.05) ATTD of Ca than LFB. Diet ß-glucan content was not correlated with STTD of P (R2 = 0.03) or ATTD of InsP6 (R2 = 0.05). In conclusion, cereal grains high in fermentable fiber, e.g., amylose and ß-glucans included in specific hull-less barley cultivars, had lower diet AID, ATTD, and STTD of P, but greater ATTD of InsP6-P and sum InsP6-2-P. Carbohydrate fermentation, thus, results in greater total tract P release from InsP-P hydrolysis.

Increased fermentable carbohydrates (e.g., ß-glucan, amylose) may increase intestinal endogenous phosphorus (P) losses and thereby reduce P digestibility. The study assessed effects of cereal grains varying in fermentable carbohydrates on non-phytate-P and phytate-P. Phytate is the major binding form of P in plant seed and is incompletely degraded. Seven barrows cannulated at the terminal ileum were fed diets containing 80% of one of five cereal grains: 1) high-fermentable, high-ß-glucan, hull-less barley; 2) high-fermentable, high-amylose, hull-less barley; 3) moderate-fermentable, hull-less barley; 4) low-fermentable, hulled barley; and 5) low-fermentable wheat. Diet ileal digestibility of P was greater for low- and moderate-fermentable grain than high-fermentable grain, and diet total tract digestibility of P was greater for moderate-fermentable barley than high ß-glucan barley. Total tract digestibility of phytate-P was greater for high ß-glucan than low-fermentable barley. Total tract P release was greater for high-fermentable barley, and wheat than moderate- and low-fermentable barley. In conclusion, cereal grains high in fermentable fiber had lower diet ileal and total tract digestibility of P resulting in greater excretion of P, but greater total tract digestibility of phytate-P. Carbohydrate fermentation, thus, increases total tract P release from phytate-P degradation.

Effect of feeding acidified or fermented barley using Limosilactobacillus reuteri with or without supplemental phytase on diet nutrient digestibility in growing pigs.

Fermentation of cereal grains may degrade myo-inositol 1,2,3,4,5,6-hexakis (dihydrogen phosphate) (InsP6) thereby increasing nutrient digestibility. Effects of chemical acidification or fermentation with Limosilactobacillus (L.) reuteri with or without phytase of high ß-glucan hull-less barley grain on apparent ileal digestibility (AID) and apparent total tract digestibility (ATTD) of nutrients and gross energy (GE), standardized ileal digestibility (SID) of crude protein (CP) and amino acids (AAs), and standardized total tract digestibility (STTD) of P were assessed in growing pigs. Pigs were fed four mash barley-based diets balanced for water content: 1) unfermented barley (Control); 2) chemically acidified barley (ACD) with lactic acid and acidic acid (0.019 L/kg barley grain at a ratio of 4:1 [vol/vol]); 3) barley fermented with L. reuteri TMW 1.656 (Fermented without phytase); and 4) barley fermented with L. reuteri TMW 1.656 and phytase (Fermented with phytase; 500 FYT/kg barley grain). The acidification and fermentation treatments occurred for 24 h at 37 °C in a water bath. The four diets were fed to eight ileal-cannulated barrows (initial body weight [BW], 17.4 kg) for four 11-d periods in a double 4 × 4 Latin square. Barley grain InsP6 content of Control, ACD, Fermented without phytase, or Fermented with phytase was 1.12%, 0.59%, 0.52% dry matter (DM), or not detectable, respectively. Diet ATTD of DM, CP, Ca, and GE, digestible energy (DE), predicted net energy (NE) value, and urinary excretion of P were greater (P < 0.05) for ACD than Control. Diet ATTD of DM, CP, Ca, GE, DE and predicted NE value, urinary excretion of P was greater (P < 0.05), and diet AID of Ca and ATTD and STTD of P tended to be greater (P < 0.10) for Fermented without phytase than Control. Diet ATTD of GE was lower (P < 0.05) and diet ATTD and STTD of P, AID and ATTD of Ca was greater (P < 0.05) for Fermented with phytase than Fermented without phytase. Acidification or fermentation with/without phytase did not affect diet SID of CP and AA. In conclusion, ACD or Fermented without phytase partially degraded InsP6 in barley grain and increased diet ATTD of DM, CP, and GE, but not SID of CP and most AA in growing pigs. Fermentation with phytase entirely degraded InsP6 in barley grain and maximized P and Ca digestibility, thereby reducing the need to provide inorganic dietary P to meet P requirements of growing pigs.

Oat ß-glucan and dietary calcium and phosphorus differentially modify intestinal expression of proinflammatory cytokines and monocarboxylate transporter 1 and cecal morphology in weaned pigs.

Physiologic effects of dietary oat ß-glucan and low and high dietary calcium-phosphorus (CaP) on intestinal morphology and gene expression related to SCFA absorption, mucus production, inflammation, and peptide digestion have not been established in weaned mammals. We therefore randomized 32 weaned pigs into 4 equal groups that received a cornstarch-casein-based diet with low (65% of the Ca and P requirement) and high (125 and 115% of the Ca and P requirement, respectively) CaP levels and low- and high-CaP diets supplemented with 8.95% oat ß-glucan concentrate for 14 d. High-CaP diets downregulated duodenal expression of IL-1ß (P < 0.05) by 30% compared with low-CaP diets. Furthermore, high-CaP diets reduced (P < 0.05) cecal crypt depth by 14% compared with low-CaP diets. Dietary ß-glucan upregulated the expression of cecal MCT1 (P < 0.05) by 40% and that of colonic IL-6 (P < 0.05) by 142% compared with the control diet. Correlation analysis indicated that cecal MCT1 (r = 0.99, P < 0.001) and colonic IL-6 (r = 0.84, P < 0.05) expression was positively related to luminal butyrate and total SCFA, respectively, indicating that ß-glucan may partly modify gene expression via increased SCFA generation. In conclusion, ß-glucan and CaP levels modulated the expression of selected genes and morphology in the postweaning period, but effects were specific to intestinal segment. The present results further indicate that, in addition to being essential nutrients for bone accretion, dietary CaP level may modify the intestinal tissue response in young pigs.

Dietary calcium phosphate content and oat ß-glucan influence gastrointestinal microbiota, butyrate-producing bacteria and butyrate fermentation in weaned pigs.

This study aimed to evaluate the effects of oat ß-glucan in combination with low- and high-dietary calcium phosphate (CaP) content on gastrointestinal bacterial microbiota, prevalence of butyrate-production pathway genes and fermentation end-products in 32 weaned pigs allocated to four diets: a cornstarch-casein-based diet with low [65% of the calcium (Ca) and phosphorous (P) requirement] and high CaP content (125% and 115% of the Ca and P requirement, respectively); and low and high CaP diets supplemented with 8.95% of oat ß-glucan concentrate. Pigs were slaughtered after 14 days, and digesta were collected for quantitative PCR analysis, and quantification of short-chain fatty acids and lactate. The high CaP content reduced gastric lactate and streptococci and propionate in the large intestine. Oat ß-glucan distinctly raised gastric bacterial numbers, and colonic lactobacilli and bifidobacteria. Although not reflected by gene copies of butyrate-production pathway genes, oat ß-glucan also increased gastric, caecal and colonic butyrate concentrations, which may be favourable for intestinal development in weaned pigs. Thus, a high CaP content negatively affected the intestinal abundance of certain fermentation end-products, whereas oat ß-glucan generally enhanced bacterial numbers and activity. The results emphasize the importance of the stomach for bacterial metabolism of oat ß-glucan in weaned pigs.