Document Detail

Effect of method of conservation of timothy on endogenous nitrogen flows in lactating dairy cows.
MedLine Citation:
PMID:  20723698     Owner:  NLM     Status:  MEDLINE    
The effect of the method of conservation of forage on endogenous N (EN) secretion was studied using a 15N isotope dilution technique in 4 lactating Holstein cows selected from a replicated 3x3 Latin square. Cows were equipped with ruminal, duodenal (n=4), and ileal (n=2) cannulas. Diets comprised 44% concentrate plus first-cut timothy conserved either as hay or as restrictively (formic) or extensively (inoc) fermented silage. Crude protein contents of hay, formic, and inoc averaged 10.4, 13.6, and 14.8%, respectively. Total EN flow and free EN at the duodenum were increased with hay compared with silages but were similar when expressed as proportion of duodenal N flow, with total EN flow averaging 25.8, 23.9, and 23.9% for hay, formic, and inoc, respectively, and free EN at the duodenum averaging 11.5, 9.8, and 9.7% for hay, formic, and inoc, respectively. Flow of bacterial N at the duodenum originating from an endogenous source tended to be higher with inoc compared with formic. Overall, the proportion of bacterial N derived from endogenous sources and urea was similar between treatments, averaging 23 and 15%, respectively. In the feces, flow of EN was similar across treatments and averaged 31% of total fecal N. More than 70% of fecal EN originated from undigested secretions into the forestomach. Absorption of N from the forestomach tended to increase for silages compared with hay. In conclusion, EN represented an important fraction of N flowing at the duodenum and in the feces. The free EN and the total EN at the duodenum were altered by the different methods of forage conservation studied. Estimation of true dietary N supply and requirements of the dairy cow should allow for endogenous N flows and losses.
D R Ouellet; R Berthiaume; G Holtrop; G E Lobley; R Martineau; H Lapierre
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of dairy science     Volume:  93     ISSN:  1525-3198     ISO Abbreviation:  J. Dairy Sci.     Publication Date:  2010 Sep 
Date Detail:
Created Date:  2010-08-20     Completed Date:  2010-11-30     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  2985126R     Medline TA:  J Dairy Sci     Country:  United States    
Other Details:
Languages:  eng     Pagination:  4252-61     Citation Subset:  IM    
Copyright Information:
Copyright (c) 2010 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.
Dairy and Swine Research and Development Centre, Agriculture and Agri-Food Canada, STN Lennoxville, Sherbrooke, Quebec, Canada J1M 1Z3.
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MeSH Terms
Ammonia / metabolism
Cattle / metabolism*,  physiology
Dairying / methods*
Diet / veterinary*
Feces / chemistry
Lactation / physiology
Nitrogen / analysis,  metabolism*
Urea / metabolism,  urine
Reg. No./Substance:
57-13-6/Urea; 7664-41-7/Ammonia; 7727-37-9/Nitrogen

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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