Estimation of Microbial Nitrogen Flow to the Duodenum of Cattle Based on Dry Matter Intake and Diet Composition

¹ Department of Animal Sciences, The Ohio State University, Columbus 43210

The objectives of this study were: 1) to evaluate the National Research Council equation used to predict microbial N flow to the duodenum in lactating cows, and 2) to determine whether improved equations could be developed by using dietary parameters used in the field. Treatment means from 55 trials with lactating and nonlactating cattle with duodenal cannulas were subjected to the backward elimination procedure of multiple regression. Variation within and among trials was accounted for by weighting the observations and including trial effects in all models. The equations to predict microbial N flow based on net energy for lactation (NE_L) intake were different from the equation based on NE_L intake used by the dairy National Research Council. Dry matter intake (DMI) estimated microbial N flow as well as did NE_L intake, indicating that DMI drives predictions based on NE_L intake. When multiple dietary factors [i.e., DMI; dietary percentages of crude protein, forage, and neutral detergent fiber; and all two-way interactions] were included, the resulting equation [microbial N (grams per day) = 16.1 + 22.9 x DMI (kilograms per day) – 0.365 x DMI² – 1.74 x dietary neutral detergent fiber (percentage of dry matter)] tended to fit the data better than the equations based on NE_L intake but not better than the equation based on DMI alone. The multiple-factor equation appeared to be the best overall equation for prediction; in contrast to the equation based on DMI, this equation is sensitive to diet composition. An asymptotic multiple-factor equation was developed, which may be more appropriate when extrapolating beyond the data range.

Key Words: empirical prediction • models • microbial protein • cattle

Submitted on October 22, 1998
Accepted on February 22, 1999

This article has been cited by other articles:

				A. N. Hristov, M. Vander Pol, M. Agle, S. Zaman, C. Schneider, P. Ndegwa, V. K. Vaddella, K. Johnson, K. J. Shingfield, and S. K. R. Karnati Effect of lauric acid and coconut oil on ruminal fermentation, digestion, ammonia losses from manure, and milk fatty acid composition in lactating cows J Dairy Sci, November 1, 2009; 92(11): 5561 - 5582. [Abstract] [Full Text] [PDF]

				A. F. Brito, G. F. Tremblay, H. Lapierre, A. Bertrand, Y. Castonguay, G. Belanger, R. Michaud, C. Benchaar, D. R. Ouellet, and R. Berthiaume Alfalfa cut at sundown and harvested as baleage increases bacterial protein synthesis in late-lactation dairy cows J Dairy Sci, March 1, 2009; 92(3): 1092 - 1107. [Abstract] [Full Text] [PDF]

				A. N. Hristov Comparative characterization of reticular and duodenal digesta and possibilities of estimating microbial outflow from the rumen based on reticular sampling in dairy cows J Anim Sci, October 1, 2007; 85(10): 2606 - 2613. [Abstract] [Full Text] [PDF]

				B. Vlaeminck, V. Fievez, S. Tamminga, R. J. Dewhurst, A. van Vuuren, D. De Brabander, and D. Demeyer Milk odd- and branched-chain Fatty acids in relation to the rumen fermentation pattern. J Dairy Sci, October 1, 2006; 89(10): 3954 - 3964. [Abstract] [Full Text] [PDF]

				J. L. Firkins, A. N. Hristov, M. B. Hall, G. A. Varga, and N. R. St-Pierre Integration of Ruminal Metabolism in Dairy Cattle J Dairy Sci, March 1, 2006; 89(e_suppl_1): E31 - E51. [Abstract] [Full Text] [PDF]

				Q. Zebeli, M. Tafaj, H. Steingass, B. Metzler, and W. Drochner Effects of Physically Effective Fiber on Digestive Processes and Milk Fat Content in Early Lactating Dairy Cows Fed Total Mixed Rations J Dairy Sci, February 1, 2006; 89(2): 651 - 668. [Abstract] [Full Text] [PDF]

				A. N. Hristov, W. J. Price, and B. Shafii A Meta-Analysis on the Relationship Between Intake of Nutrients and Body Weight with Milk Volume and Milk Protein Yield in Dairy Cows J Dairy Sci, August 1, 2005; 88(8): 2860 - 2869. [Abstract] [Full Text] [PDF]

				I. R. Ipharraguerre and J. H. Clark Impacts of the Source and Amount of Crude Protein on the Intestinal Supply of Nitrogen Fractions and Performance of Dairy Cows J Dairy Sci, May 1, 2005; 88(e_suppl_1): E22 - E37. [Abstract] [Full Text] [PDF]

				B. Vlaeminck, C. Dufour, A. M. van Vuuren, A. R. J. Cabrita, R. J. Dewhurst, D. Demeyer, and V. Fievez Use of Odd and Branched-Chain Fatty Acids in Rumen Contents and Milk as a Potential Microbial Marker J Dairy Sci, March 1, 2005; 88(3): 1031 - 1042. [Abstract] [Full Text] [PDF]

				A. N. Hristov, R. P. Etter, J. K. Ropp, and K. L. Grandeen Effect of dietary crude protein level and degradability on ruminal fermentation and nitrogen utilization in lactating dairy cows J Anim Sci, November 1, 2004; 82(11): 3219 - 3229. [Abstract] [Full Text] [PDF]

				A. N. Hristov, W. J. Price, and B. Shafii A Meta-Analysis Examining the Relationship Among Dietary Factors, Dry Matter Intake, and Milk and Milk Protein Yield in Dairy Cows J Dairy Sci, July 1, 2004; 87(7): 2184 - 2196. [Abstract] [Full Text] [PDF]

				J. A. N. Mills, E. Kebreab, C. M. Yates, L. A. Crompton, S. B. Cammell, M. S. Dhanoa, R. E. Agnew, and J. France Alternative approaches to predicting methane emissions from dairy cows J Anim Sci, December 1, 2003; 81(12): 3141 - 3150. [Abstract] [Full Text] [PDF]