Ruminal Nitrogen Recycling and Nitrogen Efficiency in Lactating Dairy Cattle

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dc.contributor.authorAguilar, Michelleen
dc.contributor.committeechairHanigan, Mark D.en
dc.contributor.committeememberJames, Robert E.en
dc.contributor.committeememberAkers, Robert Michaelen
dc.contributor.departmentDairy Scienceen
dc.date.accessioned2017-04-04T19:49:34Zen
dc.date.adate2012-08-15en
dc.date.available2017-04-04T19:49:34Zen
dc.date.issued2012-07-10en
dc.date.rdate2016-09-27en
dc.date.sdate2012-07-24en
dc.description.abstractExcess nitrogen (N) excretion from animal agriculture results in reduced air and water quality, and poses a risk to human health. Although the dairy industry utilizes milk urea N (MUN) to monitor protein feeding and N excretion, phenotypic diversity among cows may influence MUN and thus bias feed management. An initial study using data from 2 previously published research trials and a field trial, observed that cow had a significant effect on MUN variation. Regression models, utilized to predict MUN, corrected for dietary nutrients and some animal effects, and thus the observed effect of cow on MUN variation may reflect genetic selection decisions of animals with either poor or efficient urea transport. A second trial observed that MUN and PUN concentrations were positively correlated with gut urea clearance, providing evidence for differences in urea transport activity among cows. The presence of urea transport variation suggests that current protein recommendations may not estimate true requirements. A third trial observed that animals fed sub-NRC levels of RDP and RUP had reduced N intake and excretion of fecal N, urinary urea-N, and MUN. Animals maximized N efficiency and had no loss in milk production, suggesting a possible overestimation of RDP and RUP in the current NRC prediction model. The present project provides evidence for phenotypic variation among cows, which may be partially explained by differences in urea transport activity. Future work confirming genetic variation among urea transporters may provide an opportunity to improve feeding management if cow urea efficiency is known.en
dc.description.degreeMaster of Scienceen
dc.identifier.otheretd-07242012-133749en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-07242012-133749/en
dc.identifier.urihttp://hdl.handle.net/10919/76829en
dc.language.isoen_USen
dc.publisherVirginia Techen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectfeeding managementen
dc.subjectmilk urea nitrogenen
dc.subjectdietary proteinen
dc.subjectnitrogen recyclingen
dc.titleRuminal Nitrogen Recycling and Nitrogen Efficiency in Lactating Dairy Cattleen
dc.typeThesisen
dc.type.dcmitypeTexten
thesis.degree.disciplineDairy Scienceen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen

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