4MERTENS D R.Creating a system for meeting the fi- ber requirements of dairy cows [ J ]. Journal of Dairy Science, 1997,80(7) : 1463-1481.
5SCHWAB E C, SHAVER R D, SHINNERS K J, et al. Processing and chop length effects in Brown-Midrib corn silage on intake, digestion, and milk production by dairy cows[J]. Journal of Dairy Science, 2002,85 (3) : 613-623.
6TAFAJ M, ZEBELI Q, BAES C, et al. A meta-analysis examining effects of particle size of total mixed rations on intake, rumen digestion and milk production in high-yielding dairy cows in early lactation[ J] .Animal Feed Science and Technology, 2007, 138 ( 2 ) : 137- 161.
7NRC. Nutrient requirements of dairy cattle [ S ]. 7th ed. Washington, D.C. : National Academy Press, 2001.
8HEINRICHS A J, KONONOFF P J. Evaluating parti- cle size of forages and TMRs using the Penn State Particle Separator[ EB/OL ]. [ 2010-06-01 ]. http :// www. vetm ed. wsu. edu/courses-jmgay/ documents/ DAS02421.pdf.
9ZHOU J, BRUNS M A, TIEDJE J M. DNA recovery from soils of diverse composition [ J ]. Applied and En- vironmental Microbiology, 1996,62 ( 2 ) : 316-322.
10MUYZER G, DE WAAL E C, UITTERLINDEN A G. Profiling of complex microbial populations by dena- turing gradient gel electrophoresis analysis of polymer- ase chain reaction-amplified genes coding for 16S rRNA[J]. Applied and environmental microbiology, 1993,59(3) :695-700.