AOAC. (1990). Official Methods of Analysis. Vol. I. 15th Ed. Association of Official Analytical Chemists, Arlington, VA.
Broderick G.A. and Clayton M.K. (1997). A statistical evaluation of animal and nutritional factors influencing concentrations of milk urea nitrogen. J. Dairy Sci. 80, 2964-2971.
Broderick G.A. (2003). Effects of varying dietary protein and energy levels on the production of lactating dairy cows. J. Dairy Sci. 86, 1370-1381.
Bucholtz H. and Johnson T. (2007). Use of milk urea nitrogen in herd management. Paper presented at: Tri-State Dairy Nutrition Conference. Pages 63-67 in Proc. Tri-State Dairy Nutrition. Conf., Indiana, USA.
Carlsson J. and Pehrson B. (1994). The influence of the dietary balance between energy and protein on milk urea concentration. Experimental trials assessed by two different protein evaluation systems. Acta Vet. Scand. 35, 193-205.
Chaney A. and Marbach E.P. (1962). Modified reagents for determination of urea and ammonia. Clin. Chem. 8, 130-132.
Cunningham K.D., Cecava M.J., Johnson T.R. and Ludden P.A. (1996). Influence of source and amount of dietary protein on milk yield by cows in early lactation. J. Dairy Sci. 79, 620-630.
Davidson S., Hopkins B.A., Diaz D.E., Bolt S.M., Brownie C., Fellner V. and Whitlow L.W. (2003). Effects of amounts and degradability of dietary protein on lactation, nitrogen utilization, and excretion in early lactation Holstein cows. J. Dairy Sci. 86, 1681-1689.
Flis S.A. and Wattiaux M.A. (2005). Effects of parity and supply of rumen degraded and undegraded protein on production and nitrogen balance in Holsteins dairy cows. J. Dairy Sci. 88, 2096-2106.
Frank B. and Swensson C. (2002). Relationship between content of crude protein in rations for dairy cows and milk yield, concentration of urea in milk, and ammonia emissions. J. Dairy Sci. 85, 1829-1838.
Goering H.K. and Van Soest P.J. (1970). Forage Fiber Analyses. Washington, DC: Agricultural Research Service, United States Department of Agriculture. Handbook No. 379.
Groff E.B. and Wu Z. (2005). Milk production and nitrogen excretion of dairy cows fed different amounts of protein and carrying proportions of alfalfa and corn silage. J. Dairy Sci. 88, 3619-3632.
Gustafsson A.H. and Carlsson J. (1993). Effects of silage quality, protein evaluation systems, and milk urea content on milk yield and reproduction in dairy cows. Livest. Prod. Sci. 37, 91-105.
Haig P.A., Mutsvangwa T., Spratt R. and McBride B.W. (2002). Effects of dietary protein solubility on nitrogen losses from lactating dairy cows and comparison with predictions from the cornell net carbohydrate and protein system. J. Dairy Sci. 85, 1208-1217.
Higginbotham G.E., Huber J.T., Wallentine M.V., Johnston N.P. and Andrus D. (1989). Influence of protein percentage and degradability on performance of lactating cows during moderate temperature. J. Dairy Sci. 72, 1818-1823.
HofG., Vervoorn M.D., Lenaers P.J. and Tamminga S. (1997). Milk urea nitrogen as a tool to monitor protein nutrition of dairy cows. J. Dairy Sci. 80, 3333-3340.
Huber J.T., Higginbotham G.R., Gomez-Alcron A., Taylor R.B., Chen K.H., Chan S.C. and Wu Z. (1994). Heat stress interactions with protein, supplemental fat and fungal cultures. J. Dairy Sci. 77, 2080-2090.
Ipharraguerre I.R. (2004). Nutritional strategies for optimizing nitrogen utilization by dairy cows. Ph.D. Thesis, Universityof Illinois, Urbana.
Jonker J.S., Kohn R.A. and Erdman R.A. (1998). Using milk urea nitrogen to predict nitrogen excretion and utilization efficiency in lactating dairy cows. J. Dairy Sci. 81, 2681-2692.
Kalscheur K.F., Baldwin R.L., Glenn B.P. and Kohn R.A. (2006). Milk production of dairy cows fed differing concentrations of rumen-degraded protein. J. Dairy Sci. 89, 249-259.
Kauffman A.J. and St-Pierre N.R. (2001). The relationship of milk urea nitrogen to urine nitrogen excretion in Holstein and Jersey cows. J. Dairy Sci. 84, 2284-2294.
Kirchgessner M., Kreuzer M. and Roth-Maier D.A. (1986). Milk urea and protein content to diagnose energy and protein malnutrition of dairy cows. Arch. Anim. Nutr. 36, 192-197.
Kohn R.A., Janker J.S., Erdman R.E. and High J. (1997). Milk urea nitrogen: theory and practice. Pages 83-90. in Proc. Maryland Nutr. Conf., Maryland University, College Park, Baltimore, USA.
Kohn R.A., Kalscheur K.F. and Russek-Cohen E. (2002). Evaluation of models to estimate urinary nitrogen and expected milk urea nitrogen. J. Dairy Sci. 85, 227-233.
Kung L. and Huber J.T. (1983). Performance of high producing cows in early lactation fed protein of varying amounts, sources and degradabilities. J. Dairy Sci. 66, 227-234.
Leonardi C., Stevenson M. and Armentano L.E. (2003). Effect of two levels of crude protein and methionine supplementation on performance of dairy cows. J. Dairy Sci. 86, 4033-4042.
Moharrery A. (2004). Investigation of different levels of RDP in the rations of lactating cows and their effects on MUN, BUN and urinary N excretion. Ital. J. Anim. Sci. 3, 157-165.
NRC. (2001). Nutrient Requirements of Dairy Cattle. 7th rev. Ed. National Academy Press, Washington, DC, USA.
Nousiainen J., Shingfield K.J. and Huhtanen P. (2004). Evaluation of milk urea nitrogen as a diagnostic of protein feeding. J. Dairy Sci. 87, 386-398.
Oltner R. and Wiktorsson H. (1983). Urea concentrations in milk and blood as influenced by feeding various amounts of protein and energy to dairy cows. Livest. Prod. Sci. 10, 457-467.
Reynal S.M. and Broderick G.A. (2005). Effect of dietary level of rumen-degraded protein on production and nitrogen metabolism in lactating dairy cows. J. Dairy Sci. 88, 4045-4064.
Roseler D.K., Ferguson J.D., Sniffen C.J. and Herrema J. (1993). Dietary protein degradability effects on plasma and milk urea nitrogen and milk nonprotein nitrogen in Holstein cows. J. Dairy Sci. 76, 525-534.
Sannes R.A., Messman M.A. and Vagnoni D.B. (2002). Form of rumen degradable carbohydrate and nitrogen on microbial protein synthesis and protein efficiency of dairy cows. J. Dairy Sci. 85, 900-908.
SAS/STAT. (2002). SAS institute inc, cary, NC USA. Version 126.96.36.1990.
Sutton J.D. (1989). Altering milk composition by feeding. J. Dairy Sci. 72, 2801-2814.
Wattiaux M.A. and Karg K.L. (2004). Protein level for alfalfa and corn silage based diets. I. Lactational response and milk urea nitrogen. J. Dairy Sci. 87, 3480-3491.
Zhai S.W., Liu J.X., Wu Y.M., Ye J.A. and Xu Y.N. (2006). Responses of milk urea nitrogen content to dietary crude protein level and degradability in lactating Holstein dairy cows. Czech J. Anim. Sci. 51, 518-522.