Nitrogen and carbon balance of lactating Holstein cows during early and midlactation

Thirty six Holstein cows in their first, second, third or fourth lactation were used in 2 x 2 factorial design to evaluate nitrogen (N) and carbon (C) partitioning to milk, urine, feces, and body tissue during early and midlactation. Diets containing 16% CP were formulated with 30 or 39% rumen undegradable protein (RUP) obtained by substituting blood meal (EM) for soybean meal (SBM). Each level ofRUP was formulated with supplemental phosphorus from mono- and dicalcium phosphate or wheat bran. Dry matter intake was higher in midlactation compared with early lactation, and increased as parity increased. Addition of BM to the diets decreased milk protein percentage and yield compared with SBM. Fecal N excretion was higher for cows fed BM due to lower N digestibility (67 versus 63%). Cows fed SBM retained more N and partitioned more N into milk than cows fed BM. Cows partitioned approximately 49, 40, and 11% of absorbed N to urine, milk, and tissue, respectively. Concentration of plasma urea N was correlated with milk urea N (r = .50). Overall, data indicated that cows fed 16% dietary CP with SBM or BM met their requirements for milk and tissue protein synthesis. Carbon partitioning was very similar to N partitioning in response to parity. Using a fermentation balance equation, it was estimated that .3 and 3.1 kg C were partitioned daily to methane and carbon dioxide, respectively. Estimated data indicated that 36% of intake C and 57% of absorbed C were lost to the atmosphere as carbon dioxide plus methane.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Dairy Science

Department dc:contributor.department

Dairy Science

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

1996

Author dc:creator

• Eun, Jongsu

Chair dc:contributor.committeechair

• Herbein, Joseph H. Jr.

Committee members dc:contributor.committeemember

• Polan, Carl E.
• McGilliard, Michael L.
• Vinson, William E.

• carbon dioxide
• Nitrogen
• carbon
• soybean meal
• blood meal
• methane

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Dc Identifier Other

etd-02132009-170916

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/41015