Title: Influence of wet distillers grains diets on beef cattle fecal bacterial community structure Authors
|Galyean, Michael -|
|Cox, Stephanie -|
|Dowd, Scot -|
Submitted to: BMC Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 29, 2011
Publication Date: February 24, 2012
Citation: Rice, W.C., Galyean, M., Cox, S., Dowd, S.E., Cole, N.A. 2012. Influence of wet distillers grains diets on beef cattle fecal bacterial community structure. BMC Microbiology. 12:25. Interpretive Summary: The high demand for ethanol in the U.S. has generated large stocks of wet distiller’s grains (DG), a byproduct from the manufacture of ethanol from corn and sorghum grains. However little is known about the potential influence of dietary DG on the types and quantities of bacteria in the feces. A better understanding the microbial population in beef cattle feces could be important in improving nutrient management, increasing animal growth performance and in decreasing odors and/or shedding of pathogens. This study was designed to evaluate the influence of five beef cattle diets on bacteria in feces. The diets consisted of a traditional finishing diet fed to beef cattle in the Southern High Plains of Texas steam flaked corn-based with no DG, and four concentrations of DGs; 10% corn-based DG, 5% sorghum-based DG, 10% sorghum DG, and 15% sorghum DG. All diets had a crude protein value of 13.5%. We collected fecal samples from 20 steers (4/diet) used in an animal performance study at Texas Tech University. The types of bacteria in the feces were determined using a number of sophisticated laboratory and statistical techniques. Some bacteria were present in the feces of all the animals sampled, whereas other microbes were present in only individual animals or in feces from animals on specific dietary treatments. The diet fed had an effect on the microbes present in the feces. Additional studies are required to determine if, or how, these changes may relate to animal performance and nutrient utilization, or to gas production from feedlot pens.
Technical Abstract: The high demand for ethanol in the U.S. has generated large stocks of wet distillers grains (DG), a byproduct from the manufacture of ethanol from corn and sorghum grains. Little is known, however, about the potential influence of dietary DG on fecal microbial community structure. A better understanding of the microbial population in beef cattle feces could be important monitoring tool to facilitate goals of improving nutrient management, increasing animal growth performance and in decreasing odors and/or shedding of pathogens. Five diets consisting of a traditional diet fed to beef cattle in the Southern High Plains of Texas - CON (steam-flaked corn control with 0% DG), and four concentrations of DG in the dietary dry matter; 10C (10% corn-based DG), 5S (5% sorghum-based DG), 10S (10% sorghum DG), and 15S (15% sorghum DG). Diets were essentially isonitrogenous with a formulated crude protein value of 13.5%. Fecal grab samples were obtained from 20 steers (n=4 per diet) and the barcoded DNA pyrosequencing method was used to generate 127,530 16S operational taxonomic units (OTUs). A total of 24 phyla were observed distributed amongst all beef cattle on all diets revealing considerable animal to animal variation, however only six phyla (core set) were observed in all animals regardless of dietary treatment. The average abundance and range of abundance, respectively of the core phyla were as follows: Firmicutes (61%, 19 to 83%), Bacteroidetes (28%, 11to 63%), Proteobacteria (3%, 0.34 to 17.5%), Tenericutes (0.15%, 0.0 to 0.35%), Nitrospirae (0.11%, 0.03 to 0.22%), and Fusobacteria (0.086%, 0.017 to 0.38%). Feeding DG-based diets resulted in significant shifts in the fecal microbial community structure compared with the traditional CON. This effect was revealed in a variety of diversity assessments, in heat maps based on double cluster analysis, in bi-plots based on dbRDA analysis of community structure, and in one-way ANOVA of treatments. Four low abundance phyla significantly responded to dietary treatments: Synergistetes (p=0.01), WS3 (p=0.054), Actinobacteria (p=0.06), and Spirochaetes (p=0.06).