TY - JOUR
T1 - Comparison of the ruminal metabolism of nitrogen from 15N-labeled alfalfa preserved as hay or as silage
AU - Hristov, A. N.
AU - Huhtanen, P.
AU - Rode, L. M.
AU - Acharya, S. N.
AU - McAllister, T. A.
N1 - Funding Information:
Received March 28, 2001. Accepted July 18, 2001. Corresponding author: A. N. Hristov; e-mail: ahristov@uidaho.edu. 1This study was partially supported by funds from the Alberta Agricultural Research Institute and the Matching Investment Initiative of Agriculture and Agri-Food Canada. This is LRC contribution number 3870056. 2Current address: Department of Animal and Veterinary Science, University of Idaho, Moscow, 83844-2330. 3Current address: Rosebud Technology Development Ltd., 3302 Beauvais Pl. S., Lethbridge, Alberta, Canada T1K 3J5.
PY - 2001/12
Y1 - 2001/12
N2 - 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.
AB - 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.
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U2 - 10.3168/jds.S0022-0302(01)74728-5
DO - 10.3168/jds.S0022-0302(01)74728-5
M3 - Article
C2 - 11814030
AN - SCOPUS:0035751502
VL - 84
SP - 2738
EP - 2750
JO - Journal of Dairy Science
JF - Journal of Dairy Science
SN - 0022-0302
IS - 12
ER -