Comparison of the Ruminal Metabolism of Nitrogen from 15N-Labeled Alfalfa Preserved as Hay or as Silage
- 1 December 2001
- journal article
- research article
- Published by American Dairy Science Association in Journal of Dairy Science
- Vol. 84 (12), 2738-2750
- https://doi.org/10.3168/jds.s0022-0302(01)74728-5
Abstract
Alfalfa (Medicago sativa L. cv. AC Blue J) was labeled with 15N during growth in a greenhouse, harvested at early bloom, and preserved as silage (19% dry matter) or as sun-cured hay. The labeled silage and hay were given as single-pulse doses to two lactating Holstein cows fed diets comprising 30% concentrate and 70% alfalfa forage (preserved either as silage or as hay). Labeled forage and ruminal content samples collected for 72 h after dosing were partitioned into N fractions and analyzed for 15N-enrichment. Pool sizes of N compartments and kinetics in the rumen were derived by isotope dilution and by gravimetric measurements. The rate of outflow of total N, determined gravimetrically, was 21% higher with the silage diet than with the hay diet. On both diets, the largest individual flux was associated with the nonprotein, nonammonia, nonmicrobial nitrogen (NPAM-N) pool. As related to the flux of 15N through the acid detergent insoluble N pool, less tracer passed through the solid-phase nonfiber N and the soluble protein-N pools, and more passed through the NPAM-N pool, with silage than with hay. The solid-phase nonfiber N pool, which includes readily available feed N and adherent bacterial- and protozoal-N, constituted the largest N entity in the rumen, followed by the NPAM-N pool. When the forage component of the diet was alfalfa silage, N flux through the NPAM-N pool was remarkably high, and with both methods of preserving alfalfa forage, the exchange of tracer was most intensive through this pool.Keywords
This publication has 46 references indexed in Scilit:
- Proteolysis and rumen degradability of protein in alfalfa preserved as silage, wilted silage or hayAnimal Feed Science and Technology, 1998
- Distillation solution with and without indicator for nitrogen‐15 measurement by optical emission spectrometryCommunications in Soil Science and Plant Analysis, 1996
- Effect of rumen degradation on intestinal digestion of nitrogen of 15N-labelled rapeseed meal and straw measured by the mobile-bag method in cowsThe Journal of Agricultural Science, 1995
- Effect of fermentation and bacterial inoculation on lucerne cell wallsJournal of the Science of Food and Agriculture, 1992
- A comparison of methods for determining the concentration of extracellular peptides in rumen fluid of sheepThe Journal of Agricultural Science, 1990
- Response of lactating goats to low phosphorus intake 2. Nitrogen transfer from rumen ammonia to rumen microbes and proportion of milk protein derived from microbial amino acidsThe Journal of Agricultural Science, 1988
- Estimation of microbial nitrogen in nylon-bag residues by feed15N dilutionBritish Journal of Nutrition, 1985
- Observations onrumen ammonia metabolism in lactating dairy cowsThe Journal of Agricultural Science, 1980
- Investigation of chromium, cerium and cobalt as markers in digesta. Rate of passage studiesJournal of the Science of Food and Agriculture, 1980
- Isotope techniques for studying the dynamics of nitrogen metabolism in ruminantsProceedings of the Nutrition Society, 1974