Submitted to: Journal of Animal Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/21/2009
Publication Date: 9/25/2009
Citation: Weber, T.E., Trabue, S.L., Ziemer, C.J., Kerr, B.J. 2009. Evaluation of Elevated Dietary Corn Fiber from Corn Germ Meal in Growing Female Pigs. Journal of Animal Science. 88:192-201. Interpretive Summary: With the expansion of the corn ethanol industry there has been an increase in the availability of co-products that are high in corn fiber. Solvent-extracted corn germ meal is a corn co-product that is relatively high in insoluble fiber and was used in the current study to determine the impact of increasing the dietary level of corn fiber on growth performance and indices of energy metabolism. This experiment demonstrated that growing pigs can tolerate up to 38% dietary corn germ meal without any negative effects on growth performance and that changes in the expression of certain genes and metabolites are involved in the adaptive response to dietary corn fiber. This information is important for nutritionists and scientists at universities, feed companies, and swine production facilities in that it demonstrates the pig's capacity to utilize dietary fiber from corn and candidate genes that may regulate the response to dietary fiber.
Technical Abstract: To evaluate the effects of high dietary corn fiber on growth and metabolic measures, female pigs (n= 48; initial body weight of 30.8 kg) were fed diets containing 0 to 38.6% solvent-extracted corn germ meal for 28 days. Increasing the level of dietary corn fiber had no impact on average daily gain or feed intake, but resulted in a quadratic response (P < 0.03) on feed efficiency. At the completion of the growth study, colon contents and tissue samples from the liver and intestine were obtained from a subset (n = 16; 8 pigs/treatment) of pigs fed the lowest and highest fiber levels. Several plasma energy metabolites, insulin, and colonic volatile fatty acids were also determined. The liver was weighed and glycogen and triglyceride content were determined. Mucosal alkaline phosphatase and sucrase activities were determined for the jejunum and ileum. The abundance of phospho-AMP-activated protein kinase (AMPK) and the mitochondrial respiratory protein, cytochrome C oxidase II (COXII), were determined in liver, jejunum, ileum, and colon by western blotting. The relative abundance of AMPK-alpha-1, AMPK-alpha-2, peroxisome proliferator activated receptor coactivator 1-alpha (PGC1-alpha), peroxisome proliferator activated receptor (PPAR-gamma) and sirtuin 1 (Sirt1) mRNAs were determined in liver and intestinal tissues. 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 phospho-AMPK, AMPK mRNA or colonic VFA, 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 PGC1-alpha, PPAR-gamma 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 < 0.09) relative abundance of Sirt1 mRNA and a trend (P < 0.12) toward increased relative abundance of PGC1-alpha mRNA. These data suggests that alterations in metabolism involved in adaptation to high fiber diets are associated with increased colonic Sirt1 mRNA and COXII gene expression. These alterations do not appear to be mediated by AMPK in liver or intestine.