Abstract

Accurate quantitative information on the fate of dietary protein in the rumen is central to modern metabolizable protein systems developed to improve the efficiency of nitrogen utilization in ruminants. An in vitro method was developed to estimate the rate of soluble rapeseed meal (Brassica rapa L.) protein (SRMP) degradation. Unlabeled and N-15-labeled solvent-extracted rapeseed meal were incubated alone or as an equal mixture (125 mg of N/L) with buffered rumen contents and a mixture of carbohydrates formulated to provide a constant source of fermentable energy during the course of all incubations. Incubations were made over 0.33, 0.67, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 6.0, 8.0, and 10.0 h. Enrichment of N-14 and N-15 isotopes in total N of ammonia (AN), soluble nonammonia (SNAN), and insoluble (ISN) fractions liberated during incubations with test proteins was determined. A model with 4 pools that accounted for both intracellular and extracellular N transformations was used to estimate the rate of SRMP degradation. Parameter values used in the model were adjusted based on the size of A(14)N, A(15)N, SNA(14)N, SNA(15)N, (ISN)-N-14, and (ISN)-N-15 pools, measured at different time points during incubations with buffered rumen fluid. The mean rate of N degradation for SRMP was estimated at 0.126 (SD 0.0499) h(-1). No substantive difference in the rate of protein degradation or microbial protein synthesis was observed during incubations of labeled and unlabeled substrates with rumen fluid. In conclusion, combined use of data from incubations of unlabeled and N-15-labeled rapeseed protein with buffered rumen inoculum provided sufficient information to allow for estimation of parameter values in a complex dynamic model of soluble protein degradation. Results indicate the potential of the technique to evaluate the degradability of SNAN of other dietary protein sources and implicate ruminal escape of soluble rapeseed protein as an important source of amino acids in ruminants.

Keywords

rapeseed; nitrogen; N-15; soluble protein

Published in

Journal of Dairy Science
2013, Volume: 96, number: 1, pages: 440-450
Publisher: ELSEVIER SCIENCE INC

SLU Authors

• Huhtanen, Pekka

  • Agrifood Research Finland (MTT)
  • Department of Agricultural Research for Northern Sweden, Swedish University of Agricultural Sciences
    

Sustainable Development Goals

SDG2 End hunger, achieve food security and improved nutrition and promote sustainable agriculture


UKÄ Subject classification

Animal and Dairy Science
Agricultural Science


Publication identifier

DOI: https://doi.org/10.3168/jds.2012-5642

Permanent link to this page (URI)

https://res.slu.se/id/publ/53716