EFFECTS OF FEEDING SOLUBLE FIBER (DEXTRIN) TO PIGS PRE- AND POST-WEANING ON GROWTH PERFORMANCE, INTESTINAL MICROBIOME, VOLATILE FATTY ACID (VFA) PRODUCTION, INTESTINAL MORPHOLOGY, AND GENE EXPRESSION
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Forty barrows were used in a 35d experiment to evaluate the effects of supplemental soluble fiber (dextrin) pre- and post-weaning on growth performance, intestinal microbiome, volatile fatty acid (VFA) production, intestinal morphology, and gene expression. Pigs were blocked by litter and BW, and randomly allotted to treatments in a 2x2 factorial design with or without fiber pre-weaning and with or without fiber post-weaning. Dextrin was administered orally through a syringe, after being suspended in chocolate milk from 14d prior to weaning through 3d post-weaning, after which it was included in the diet at 1%. At weaning, pigs were group housed by treatment and allowed ad libitum access to a common starter diet. On d4 post-weaning, pigs were moved to individual pens and fed diets with or without 1% fiber. Weights and feed intake were recorded 14 and 3d prior to weaning, and on d0, 4, 11, and 21 post-weaning. On d0 and d21 post-weaning, pigs were euthanized for collection of tissues and intestinal contents. Ileal, cecal, and colon contents were taken for microbiome analysis, distal large intestine contents were collected for VFA analysis, ileal cross sections were collected for histology, and ileal and cecal mucosal scrapings were collected for intestinal gene expression. Data were analyzed using the GLM procedure of SAS with pig as the experimental unit for growth performance, VFA production, intestinal morphology, and gene expression. Microbiome data were analyzed using Metastats, to find statistical significance between treatments, and then run through R, using the false discovery rate method, to find a multiple test corrections q-value. Growth performance in general was not affected (P> 0.10) by treatment with the exception of d11-21 feed efficiency was improved (P= 0.018) for pigs receiving supplemental fiber prior to weaning. Pigs that received fiber at any point had increased short chain fatty acid (SCFA) producing bacteria (q < 0.05) compared to pigs never receiving fiber. Pigs never receiving fiber had increased bacteria associated with intestinal inflammation (q < 0.05) compared to all other treatment groups. A trend for an interaction (P = 0.054) of pre- and post-weaning fiber supplementationwas observed for total volatile fatty acid concentration in large intestine contents. An interaction (P = 0.007) of pre- and post-weaning treatments was observed on butyrate, with pigs fed fiber only during pre-weaning having the greatest butyrate concentrations. Pigs fed fiber pre-weaning had decreased isobutyrate concentrations (P = 0.050) and percentages (P=0.040) and a trend for decreased isovalerate as a concentration (P= 0.058) and percent of total VFAs (P = 0.051). Pigs fed fiber post-weaning had increased acetate (P = 0.047). An interaction for butyrate percentages was observed with pigs receiving supplemental fiber only prior to weaning having the highest percent of butyrate (P= 0.029). An interaction for valerate concentrations (P = 0.045) occurred with pigs receiving fiber only prior to weaning having the highest amount of valerate. Valerate as a proportion of total VFAs (P = 0.038) was decreased in pigs receiving supplemental fiber post-weaning. Pigs fed fiber prior to weaning tended to have decreased crypt depths (P = 0.097) compared to pigs that did not receive fiber prior to weaning. In the ileum there was an interaction (P = 0.002) for GLP-2 expression, with pigs receiving supplemental fiber solely before or after weaning having the greatest expression. Occludin expression in the ileum tended to increase with fiber supplementation prior to weaning (P= 0.086) but then tended to decrease with fiber supplementation post-weaning (P= 0.053) In the cecum, there was an interaction (P = 0.049) of pre- and post-weaning fiber supplementationon GLP-2 expression. Pigs fed supplemental fiber at any point had increased GLP-2 expression, but pigs that had fiber only after weaning had the greatest GLP-2 expression. Cecal HSP-70 expression also increased with fiber supplementation in pigs fed fiber post-weaning (P = 0.012). Soluble fiber supplementation caused alterations in the intestinal microbiome, VFA concentrations, the intestinal morphology, and in the expression of different intestinal genes.