Submitted to: Meeting Proceedings
Publication Type: Abstract only
Publication Acceptance Date: 9/23/2008
Publication Date: 11/16/2008
Citation: Weber, T.E., Kerr, B.J. 2008. Metabolic Effects of Diets High in Corn Fiber in Growing Female Pigs [abstract]. Proceedings of Sixth International Congress on Farm Animal Endocrinology, November 14-16, 2008, Roanoke, Virginia. p. 84. Interpretive Summary:
Technical Abstract: To evaluate the effects of high dietary corn fiber on growth and metabolic measures, growing female pigs (n= 48; BW 30.8 kg) were fed diets containing 0 to 38.6% solvent-extracted corn germ meal for 28 days. Corn germ meal is relatively high in neutral detergent fiber (53%) and hemicellulose content (41%). Data show that increasing the level of dietary corn fiber had no impact on pig growth rate or feed intake, but did lead to a quadratic response (P < 0.03) in feed efficiency. At the completion of the growth portion of the study, plasma, liver and intestinal tissue samples were obtained from a subset (n = 8) of pigs from the lowest and highest dietary fiber treatment groups. Plasma energy metabolites and insulin were determined, the liver was analyzed for absolute and relative weight, and liver glycogen and triglyceride content were determined. Mucosal alkaline phosphatase and sucrase enzyme activities were determined from the jejunum and ileum. The abundance of phospho-AMP-activated protein kinase (AMPK) and the mitochondrial respiratory protein, cytochrome C oxidase II (COXII), was determined in liver, jejunum, ileum, and colon tissue by western blotting. The relative abundance of AMPKalpha1, AMPKalpha2, peroxisome proliferator activated receptor coactivator 1alpha (PGC1alpha), peroxisome proliferator activated receptor (PPARgamma) and sirtuin 1 (Sirt1) mRNAs was determined in liver and intestinal tissues via real-time RT-PCR. When compared to pigs fed the control diet, pigs fed the high fiber diet had increased (P < 0.02) plasma triglycerides, but there was no difference in plasma cholesterol, glucose, or insulin. Absolute and relative liver weights were decreased (P < 0.03) in pigs consuming the high fiber diet. The high fiber diet led to a tendency (P < 0.12) for decreased liver triglyceride content. In pigs fed the high fiber diet, ileal mucosal alkaline phosphatase activity was increased (P <0.08) and sucrase activity tended (P < 0.12) to be increased. The high fiber diet had no effect on the abundance of phospho-AMPK, or AMPK mRNA in liver or intestinal tissue, but in pigs consuming the high fiber diet there was a greater (P < 0.05) abundance of COXII in colon tissue. The relative abundance of PGC1alpha, PPARgamma or Sirt1 mRNAs was not altered by dietary fiber in liver, jejunum, or ileum tissue. In colon tissue from pigs fed the high fiber diet there was an increased (P < 0.10) relative abundance of Sirt1 mRNA and a trend (P < 0.12) towards increased relative abundance of PGC1alpha mRNA. These data suggest that alterations in metabolism involved in adaptation to a diet high in corn fiber are associated with increased colonic Sirt1 and COXII expression. Furthermore, these alterations do not appear to be mediated by AMPK activation in liver or intestinal tissue.