{"id":{"repo_id":"maryland","oai_identifier":"oai:drum.lib.umd.edu:1903/7815"},"canonical_url":"https://search.dev.ndltd.org/etd/maryland/oai:drum.lib.umd.edu:1903/7815","repository":{"repo_id":"maryland","name":"University of Maryland","base_url":"https://api.drum.lib.umd.edu/server/oai/request"},"display":{"title":"Urea-N Recycling in Lactating Dairy Cows","abstract":"This study was designed to determine the effect of rumen degradable protein (RDP) and rumen undegradable protein (RUP) on urea-N recycling and microbial N flow. Eight mid-lactation Holstein cows were assigned to a repeated 4 x 4 Latin square. The diets were isoenergetic with RDP and RUP concentrations arranged in a factorial design (10.0 and 12.5% RDP and 5.6 and 8.1% RUP as a percentage of DM). The 10.0% RDP diets resulted in greater milk yield and lower milk protein concentration than the 12.5% RDP diets. High RUP diets tended (P = 0.1) to increase bacterial N flow in the liquid fraction. The NRC 1989 model predicted flow of microbial N and total N from the rumen more accurately than the NRC 2001. The NRC 2001 model predicted a higher RDP requirement and a lower RUP requirement for all four diets compared with the NRC 1989 model. Both models reflect the dietary changes that were intended by increasing the RDP and RUP in a factorial manner. There was no effect of RUP or RDP on the g/d of urea-N transferred from the blood to the gut or returning to the ornithine-urea cycle. However, plasma urea-N (PUN) incorporated into rumen microbial protein tended (P = 0.14) to increase with the low RDP diets. The rate of transfer of PUN to the gut appeared to be independent of PUN concentrations. The gene expression for urea transporters (bUT-B2) in the rumen did not change due to diet. As dietary protein intake increased, a constant amount (g/d), or decreasing fraction (g/g), of PUN was transferred to the gut. The apparent saturation of urea transporters in the gut prevented excess PUN from recycling to the gut on high-protein diets sparing the energy cost for N excretion that would have resulted from a constant percentage of PUN being recycled.","abstract_html":"This study was designed to determine the effect of rumen degradable protein (RDP) and rumen undegradable protein (RUP) on urea-N recycling and microbial N flow. Eight mid-lactation Holstein cows were assigned to a repeated 4 x 4 Latin square. The diets were isoenergetic with RDP and RUP concentrations arranged in a factorial design (10.0 and 12.5% RDP and 5.6 and 8.1% RUP as a percentage of DM). The 10.0% RDP diets resulted in greater milk yield and lower milk protein concentration than the 12.5% RDP diets. High RUP diets tended (P = 0.1) to increase bacterial N flow in the liquid fraction. The NRC 1989 model predicted flow of microbial N and total N from the rumen more accurately than the NRC 2001. The NRC 2001 model predicted a higher RDP requirement and a lower RUP requirement for all four diets compared with the NRC 1989 model. Both models reflect the dietary changes that were intended by increasing the RDP and RUP in a factorial manner. There was no effect of RUP or RDP on the g/d of urea-N transferred from the blood to the gut or returning to the ornithine-urea cycle. However, plasma urea-N (PUN) incorporated into rumen microbial protein tended (P = 0.14) to increase with the low RDP diets. The rate of transfer of PUN to the gut appeared to be independent of PUN concentrations. The gene expression for urea transporters (bUT-B2) in the rumen did not change due to diet. As dietary protein intake increased, a constant amount (g/d), or decreasing fraction (g/g), of PUN was transferred to the gut. The apparent saturation of urea transporters in the gut prevented excess PUN from recycling to the gut on high-protein diets sparing the energy cost for N excretion that would have resulted from a constant percentage of PUN being recycled.","abstract_has_math":false,"creators":["Dinh, Sarah"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":"Animal Sciences","school":null,"contributors":[],"advisors":["Kohn, Richard A"],"committee_chairs":[],"committee_members":[],"year":2007,"date_issued":"2007-12-11","date_published":"2007-12-11","updated_at":"2026-07-24T03:02:15Z","subjects":[],"languages":["en_US"],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/1903/7815","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Kohn, Richard A"]},{"key":"dc:contributor.department","label":"Department","values":["Animal Sciences"]},{"key":"dc:creator","label":"Author","values":["Dinh, Sarah"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2008-04-22T16:09:13Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2008-04-22T16:09:13Z"]},{"key":"dc:date.issued","label":"Date","values":["2007-12-11"]},{"key":"dc:type","label":"Dc Type","values":["Dissertation"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["en_US"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/1903/7815"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["This study was designed to determine the effect of rumen degradable protein (RDP) and rumen undegradable protein (RUP) on urea-N recycling and microbial N flow. Eight mid-lactation Holstein cows were assigned to a repeated 4 x 4 Latin square. The diets were isoenergetic with RDP and RUP concentrations arranged in a factorial design (10.0 and 12.5% RDP and 5.6 and 8.1% RUP as a percentage of DM). The 10.0% RDP diets resulted in greater milk yield and lower milk protein concentration than the 12.5% RDP diets. High RUP diets tended (P = 0.1) to increase bacterial N flow in the liquid fraction. The NRC 1989 model predicted flow of microbial N and total N from the rumen more accurately than the NRC 2001. The NRC 2001 model predicted a higher RDP requirement and a lower RUP requirement for all four diets compared with the NRC 1989 model. Both models reflect the dietary changes that were intended by increasing the RDP and RUP in a factorial manner. There was no effect of RUP or RDP on the g/d of urea-N transferred from the blood to the gut or returning to the ornithine-urea cycle. However, plasma urea-N (PUN) incorporated into rumen microbial protein tended (P = 0.14) to increase with the low RDP diets. The rate of transfer of PUN to the gut appeared to be independent of PUN concentrations. The gene expression for urea transporters (bUT-B2) in the rumen did not change due to diet. As dietary protein intake increased, a constant amount (g/d), or decreasing fraction (g/g), of PUN was transferred to the gut. The apparent saturation of urea transporters in the gut prevented excess PUN from recycling to the gut on high-protein diets sparing the energy cost for N excretion that would have resulted from a constant percentage of PUN being recycled."]},{"key":"dc:format.mimetype","label":"Dc Format Mimetype","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Urea-N Recycling in Lactating Dairy Cows"]}]}],"canonical_facts":{"dc:contributor.advisor":["Kohn, Richard A"],"dc:contributor.department":["Animal Sciences"],"dc:creator":["Dinh, Sarah"],"dc:date.accessioned":["2008-04-22T16:09:13Z"],"dc:date.available":["2008-04-22T16:09:13Z"],"dc:date.issued":["2007-12-11"],"dc:description.abstract":["This study was designed to determine the effect of rumen degradable protein (RDP) and rumen undegradable protein (RUP) on urea-N recycling and microbial N flow. Eight mid-lactation Holstein cows were assigned to a repeated 4 x 4 Latin square. The diets were isoenergetic with RDP and RUP concentrations arranged in a factorial design (10.0 and 12.5% RDP and 5.6 and 8.1% RUP as a percentage of DM). The 10.0% RDP diets resulted in greater milk yield and lower milk protein concentration than the 12.5% RDP diets. High RUP diets tended (P = 0.1) to increase bacterial N flow in the liquid fraction. The NRC 1989 model predicted flow of microbial N and total N from the rumen more accurately than the NRC 2001. The NRC 2001 model predicted a higher RDP requirement and a lower RUP requirement for all four diets compared with the NRC 1989 model. Both models reflect the dietary changes that were intended by increasing the RDP and RUP in a factorial manner. There was no effect of RUP or RDP on the g/d of urea-N transferred from the blood to the gut or returning to the ornithine-urea cycle. However, plasma urea-N (PUN) incorporated into rumen microbial protein tended (P = 0.14) to increase with the low RDP diets. The rate of transfer of PUN to the gut appeared to be independent of PUN concentrations. The gene expression for urea transporters (bUT-B2) in the rumen did not change due to diet. As dietary protein intake increased, a constant amount (g/d), or decreasing fraction (g/g), of PUN was transferred to the gut. The apparent saturation of urea transporters in the gut prevented excess PUN from recycling to the gut on high-protein diets sparing the energy cost for N excretion that would have resulted from a constant percentage of PUN being recycled."],"dc:format.mimetype":["application/pdf"],"dc:identifier.uri":["http://hdl.handle.net/1903/7815"],"dc:language.iso":["en_US"],"dc:title":["Urea-N Recycling in Lactating Dairy Cows"],"dc:type":["Dissertation"]},"updated_at":"2026-07-24T03:02:15Z"}