Effects of Cow Diet on the Microbial Community and Organic Matter and Nitrogen Content of Feces

• Published in: Journal of dairy science 2007-11, Vol.90 (11), p.5146-5158
• Main Authors: van Vliet, P.C.J., Reijs, J.W., Bloem, J., Dijkstra, J., de Goede, R.G.M.
• Format: Article
• Language: English
• Subjects: 16s ribosomal-rna; Animal productions; Animals; Bacteria - classification; Bacteria - growth & development; Bacteria - isolation & purification; bacterial diversity; Biodiversity; Biological and medical sciences; Biomass; Carbon - analysis; carbon nitrogen ratio; Cattle - metabolism; Cattle - microbiology; cattle slurry; Colony Count, Microbial - veterinary; cow feeding; crude protein; dairy cows; dairy farming; decomposition; Diet - veterinary; dietary fiber; Dietary Fiber - administration & dosage; dietary protein; Dietary Proteins - administration & dosage; DNA fingerprinting; ecology; energy content; feces; Feces - chemistry; Feces - microbiology; feed concentrates; feed rations; Feeding. Feeding behavior; Female; Fundamental and applied biological sciences. Psychology; gradient gel-electrophoresis; intestinal microorganisms; management; manure; manure composition; microbial communities; mineralization; neutral detergent fiber; Nitrogen - analysis; nitrogen content; organic matter; Phylogeny; roughage; soil; species diversity; starch; Terrestrial animal productions; Vertebrates; Vertebrates: anatomy and physiology, studies on body, several organs or systems
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.2007-0065

Knowledge of the effects of cow diet on manure composition is required to improve nutrient use efficiency and to decrease emissions of N to the environment. Therefore, we performed an experiment with nonlactating cows to determine the consequences of changes in cow rations for the chemical characteristics and the traits of the microbial community in the feces. In this experiment, 16 cows were fed 8 diets, differing in crude protein, neutral detergent fiber, starch, and net energy content. These differences were achieved by changing dietary ingredients or roughage to concentrate ratio. After an adaptation period of 3 wk, fecal material was collected and analyzed. Observed results were compared with simulated values using a mechanistic model that provides insight into the mechanisms involved in the effect of dietary variation on fecal composition. Feces produced on a high-fiber, low-protein diet had a high C:N ratio (>16) and had lower concentrations of both organic and inorganic N than feces on a low-fiber, high-protein diet. Fecal bacterial biomass concentration was highest in high-protein, high-energy diets. The fraction of inorganic N in the feces was not significantly different between the different feces. Microbial biomass in the feces ranged from 1,200 to 8,000μg of C/g of dry matter (average: 3,700μg of C/g of dry matter). Bacterial diversity was similar for all fecal materials, but the different protein levels in the feeding regimens induced changes in the community structure present in the different feces. The simulated total N content (Ntotal) in the feces ranged from 1.0 to 1.5 times the observed concentrations, whereas the simulated C:Ntotal of the feces ranged from 0.7 to 0.9 times the observed C:Ntotal. However, bacterial biomass C was not predicted satisfactorily (simulated values being on average 3 times higher than observed), giving rise to further discussion on the definition of microbial C in feces. Based on these observations, it was concluded that diet composition affected fecal chemical composition and microbial biomass. These changes may affect the nutrient use and efficiency of the manure. Because the present experiment used a limited number of dry cows and extreme diet regimens, extrapolation of results to other dairy cow situations should be done with care.