Title: Whole corn and wet distiller's grains substitution in steam-flaked corn diet alters rumen fermentation and bacterial dynamics Authors
|Tracey, Laura -|
|Mcdaniel, Michael -|
|Brown-Silva, Johnette -|
|Loest, Clint -|
|Lodge-Ivey, Shanna -|
Submitted to: American Society of Animal Science Proceedings
Publication Type: Proceedings
Publication Acceptance Date: April 30, 2011
Publication Date: August 30, 2011
Citation: Tracey, L.N., McDaniel, M.R., Brown-Silva, J., Cole, N.A., Loest, C.A., Lodge-Ivey, S.L. 2011. Whole corn and wet distiller's grains substitution in steam-flaked corn diet alters rumen fermentation and bacterial dynamics. In: Proceedings of the Western Section of the 2011 American Society of Animal Science Conference, June 21-23, 2011, Miles City, Missouri. 62:330-334. Interpretive Summary: In most beef cattle feedyard diets the corn is processed to increase its digestibility. In the Southern Great Plains the predominant processing method is steam-flaking. The process of making ethanol form grain results in the byproduct called distiller's grains. Distiller's grains can be used in cattle feeds, but research suggests it is not used well in diets based on steam-flaked corn. We hypothesized that because distiller's grains are used more efficiently in diets based on less processed corn, it might be possible to replace a portion of steam-flaked corn with whole shelled corn in diets containing distiller's grains without adversely affecting animal performance or rumen function. This study was conducted to determine the effects of feeding 0 or 20% whole shelled corn in diets containing 0, 15 or 30% wet distiller's grains on rumen function and bacterial populations. Ruminal fluid from 72 heifers were analyzed for pH, ammonia, volatile fatty acids, and microbial populations. Dietary changes affected pH, volatile fatty acids concentrations, and bacterial diversity. The results suggest that shifts in microbial population and fermentation characteristics may affect the ruminal utilization of wet distiller's grains.
Technical Abstract: A study evaluated effects of whole shelled corn (WSC) in steam-flaked corn (SFC) finishing diets containing differing amounts of wet distiller's grains with solubles (WDGS) on ruminal fermentation and shifts in ruminal bacterial populations. A total of 642 heifers (initial body weight (BW) = 412 +/- 18 kg) were blocked by BW and randomly assigned to 36 pens in a 108 d experiment. Treatments were arranged as a 2 x 3 factorial with two amounts of WSC (0 and 20% DM) and three amounts of WDGS (0, 15, and 30% DM) replacing SFC. Ruminal fluid samples, collected from two heifers/pen on d 98,were analyzed for volatile fatty acids (VFA), ammonia, pH, and shifts in ruminal bacterial populations using denaturing gradient gel electrophoresis (DGGE) targeting the 16S rDNA gene. Richness and Shannon-Wiener indices evaluated bacterial presence and diversity. Similarity matrix of DGGE banding patterns were constructed using Dice (binary) coefficient. Microbial indices and ruminal samples were evaluated for effects of WSC, WDGS, and interactions using Mixed Procedure of SAS with block as the random variable and pen as experimental unit. Addition of 15% WDGS to 0% WSC diets increased total VFA concentrations; however, addition of 30% WDGS to 0% WSC diets decreased total VFA concentrations (WSC x WDGS interaction, P = 0.02). Ammonia concentrations were not affected (P >/= 0.19) by diets. Diets with 0% WSC had lower ruminal pH (P < 0.01), lower acetate molar proportions (P = 0.05), greater propionate molar proportions (P = 0.02), and lower acetate:propionate ratio (P </= 0.02) than 20% WSC diets. Inclusion of WDGS decreased acetate (quadratic, P < 0.01), increased propionate (quadratic, P = 0.03), and decreased acetate:propionate (quadratic, P = 0.03). Bacterial diversity based on DGGE, Richness, and Shannon-Wiener indices did not differ with inclusion of WSC (P = 0.63), but increased with WDGS (linear, P = 0.01). All samples were 69.02% similar according to Dice. Microbial population shifts and fermentation characteristics imply that use of WSC in SFC-based finishing diets may negatively alter ruminal use of WDGS.