1Gustafsson A H,Palmquist D L, Diurnal variation of rumen ammonia, serum urea, and milk urea in dairy cows at high and low yields[J].J Dairy Sci, 1993,(76):475-484.
2Hof G, Vervoorn M D, Lenaers P J, et al. Milk urea nitro gen as a tool to monitor the protein nutrition of dairy cows[J].J Dairy Sci, 1997,(80):3333-3340.
3Baker L D, Ferguson J D, Ramberg C F. Kinetic analysis of urea transport from plasma to milk in dairy cows [J],J Dairy Sci, 1992,75(Suppl. 1):181(Abstr).
4Jonker J S, Kohn R A, Erdman R & Using milk urea nitrogen to predict nitrogen excretion and utilization efficiency in lactating dairy cows[J].J Dairy Sci, 1998, (81):2681-2692.
5叶应妩,王毓三.全国临床检验操作规程[M].南京:东南大学出版社,1991:32.
6AOAC. Official Methods of Analysis[M].lSth ed. Assoc Offic Anal Chem, Arlington, VA. 1990.
7Nousiainen J, Shingfield K J;Huhtanen P. Evaluation of milk nitrogen as a diagnostic of protein feeding [J]. J Dairy Sci, 2004, (87) :386-398.
8Broderick G A, Clayton M K.A statistical evaluation of animal and nutritional factors influencing concentrations of milk urea nitrogen[J].J Dairy Sci, 1997, (80):2964-2971.
1Blum J W, Bruckmaier R M and Jans F. Rumen-protected methionine fed to dairy cows: Bioavailability and effects on plasma amino acid pattern and plasma metabolite and insulin concentrations [J]. J Dairy Sci, 1999, 82:1991-1998.
2Wright T C, Moscardini S, Luimes P H, Susmel P, et al. Effects of rumen-undegradable protein and feed intake on nitrogen balance and milk protein production in dairy cows [J]. J Dairy Sci, 1998, 81:784-793.
3Donkin S S, Varga G A, Sweeney T F and Muller L D. Rumen-protected methionine and lysine: effects on animal performance, milk protein yield and physiological measures [J]. J Dairy Sci, 1989, 72:1484-1489.
4Overton T R, Emmert L S and Clark J H. Effects of ssource of carbohydrate and protein and rument-protected methionine on performance of cows . J Dairy Sci, 1998, 81 : 221-228.
5Bateman H D, Spain J N, Kerley M S, et al. Evaluation of ruminally protected methionine and lysine or blood meal and fish meal as protein sources, for lactating Holsteins . J Dairy Sci, 1999, 82:2115-2120.
6Canale C J, Muller L D, Mccahom H A, et al. Dietary fat and ruminally protected amino acid for high producing dairy cows . J Dairy Sci, 1990, 73:135-141.
7Lundquist R G, Stern M D, Qtterby D E, et al. Influence of methionine hydroxy nanlog and DL-methionine on rumen protozoa and volatile fatty acids . J Dairy Sci, 1994, 68:3055-3058.