| The effect of short-term hyperammonaemia on milk synthesis in dairy cows. | |
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MedLine Citation:
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PMID: 18922195 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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To test the hypothesis that ammonia detoxification in ruminants consumes amino acids to the detriment of milk protein production, we infused four lactating dairy cows with ammonium acetate or sodium acetate in switchback experiments. Plasma ammonia concentrations increased to 411 microm within 1 h of the start of infusion of ammonium acetate at 567 mmol/h. The rate constant for ammonia clearance from plasma was 0 x 054/min and the half-life was 12 x 9 min. Infusion at 567 mmol/h for 1 h followed by 1 h without infusion, repeated four times between am- and pm-milking, caused a decrease in feed intake. Compared with sodium acetate, continuous infusion of ammonium acetate at 360 mmol/h throughout an entire 10-h milking interval increased plasma ammonia concentrations to 193 microm and caused a 20% decrease in milk, protein and lactose production with no effect on percentage composition of milk or the yield of milk fat. Arterial concentrations of glucose and non-esterified fatty acids tended to increase; there was no effect on arterial acetate, beta-hydroxybutyrate or triacylglcerol, and branched-chain amino acids, Lys and Thr decreased. Mammary plasma flow, estimated by assuming 100% uptake/output of Phe+Tyr, was significantly correlated with milk yield. Mammary uptakes of acetate tended to be reduced by hyperammonaemia, but uptakes of other energy metabolites and amino acids were not affected. Thus, while an increase in amino acid consumption during hyperammonaemia was apparent from the drop in circulating concentrations of Leu, Ile, Val, Lys and Thr, there was no evidence to support the hypothesis that milk yield is affected by the lower concentrations. An ammonia-induced depression in feed intake may have caused the decrease in milk synthesis. |
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Authors:
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Norm G Purdie; Donald R Trout; Scott R L Cieslar; Torben G Madsen; Dennis P Poppi; John P Cant |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't Date: 2008-10-16 |
Journal Detail:
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Title: The Journal of dairy research Volume: 76 ISSN: 0022-0299 ISO Abbreviation: J. Dairy Res. Publication Date: 2009 Feb |
Date Detail:
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Created Date: 2009-01-20 Completed Date: 2009-03-11 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 2985125R Medline TA: J Dairy Res Country: England |
Other Details:
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Languages: eng Pagination: 49-58 Citation Subset: IM |
Affiliation:
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Schools of Animal Studies and Veterinary Science, University of Queensland, Australia. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Acetates
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pharmacology* Amino Acids / blood, metabolism Ammonia / blood Animals Cattle Cattle Diseases / chemically induced, physiopathology* Dairying Eating / drug effects, physiology Female Hyperammonemia / chemically induced, physiopathology, veterinary* Lactation / drug effects* Mammary Glands, Animal / blood supply, metabolism Milk / chemistry, secretion Sodium Acetate / pharmacology* |
| Chemical | |
Reg. No./Substance:
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0/Acetates; 0/Amino Acids; 6131-90-4/Sodium Acetate; 631-61-8/ammonium acetate; 7664-41-7/Ammonia |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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