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High Inclusion of Distillers Dried Grains with Solubles as a Dietary Fiber Source Reduces Cytokine Levels in Growing-finishing Pigs
Dietary fiber plays an important role in the gastrointestinal inflammatory response. We hypothesized that the immune response is modulated differentially by the type of dietary fiber. Forty-six pigs (83.4 ± 6.7 kg) were divided into 4 groups and fed diets formulated with 3 different fiber sources: wheat straw (WS; n=11), corn distiller's dried grains with solubles (DDGS; n=11), and soybean hulls (SBH; n=12). A corn-soybean meal diet was used as control (CON, n=12). Test diets were formulated to contain approximately 17% NDF by adding 23% WS, 55% DDGS, or 30% SBH. Pigs were housed in metabolism cages, acclimated for 10-d and fed an amount equal to 2.5% of their initial BW for 14-d. Ileal tissue and blood samples were collected at euthanasia. To identify which genes expression in the ileum was changed, a commercial PCR array (Qiagen, PASS-011ZA) was used. The cDNA from the ileal RNA was pooled and expression of 84 immune markers; 5 housekeeping genes, and 7 quality controls were determined. Fold-change and statistical significance were calculated using Qiagen’s RT2 analysis tool and β-actin as housekeeping gene. Results with P < 0.001 were considered significant. The greatest change observed was IL23A induction by WS (256 fold) vs. DDGS (12 fold). Compared with WS, DDGS induced 2 and repressed 39 genes. Compared with SBH, DDGS induced 53 genes and repressed IL5RA. When compared with SBH, WS induced 48 and repressed 5 genes. To determine whether the type of dietary fiber alters the overall immune profile, plasma concentrations of cytokines and chemokines were measured using a porcine immunoassay panel on a Luminex 200. Fluorescent intensity data were analyzed by curve-fitting of standards to calculate sample concentrations. Group comparisons were tested by Mann-Whitney U test using GraphPad Prism 6. Overall, WS increased concentrations of cytokines while DDGS decreased them. Our results indicate that the immune response is modulated differently by type of dietary fiber source.
Table 1. Effects of dietary fiber source on the abundance of cytokine RNA in ileum.
|
Fiber Source |
|||
Marker (pg/ml) |
CON |
WS |
DDGS |
SBH |
IFNγ1 |
1122.1 |
2044.7 |
1457.1 |
5443.7 |
IL-1α |
29.7 |
13.9 |
5.5 |
40.89 |
IL-1β |
642.7 |
130.8 |
31.3 |
355.4 |
IL-1RA |
84.82a |
152.8a,b |
45.2a,c |
139.1a,b,d |
IL-2 |
217.1a |
148.9a,b |
70.3a,c |
215.6a |
IL-4 |
1212.6 |
460.0 |
125.4 |
1600.0 |
IL-6 |
264.2 |
83.9 |
84.6 |
99.4 |
IL-8 |
10.2 |
13.9 |
8.8 |
13.1 |
IL-10 |
193.5a |
87.8a,b,c |
47.2b |
102.6a,c |
IL-12 |
389.6 |
448.2 |
401.0 |
476.5 |
IL-18 |
849.8 |
525.4 |
360.1 |
561.2 |
a,b,c,d Different superscripts within each row differ (P<0.05)
Keywords: DDGS, Dietary fiber, Immune response