| Carryover effects of potassium supplementation on calcium homeostasis in dairy cows at parturition. | |
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MedLine Citation:
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PMID: 20412927 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The purpose of this study was to test whether supplementation with K improves bone mineral density (BMD) in older cows so that by parturition their bone is better able to mobilize Ca. Twenty-four Holstein Friesian cows (6 mo pregnant, lactating, and in their third or later lactation) were allocated to 2 equal groups and individually fed twice daily a total diet comprising low K oaten hay plus a pelleted concentrate fortified with or without K(2)CO(3) to achieve 3.12% K/kg of DM in the total diet of the K-supplemented (KS) cows compared with 1.50% K/kg of DM for the control cows. The cows were fed their respective diets from the beginning of their sixth month of pregnancy until 2 wk before the expected date of parturition. The strategy was to use K to stimulate a mild increase in extracellular pH to potentially improve BMD well before parturition, when high K contents in the diet are considered safe, but cease supplementing in the few weeks prepartum, when high intakes of K are known to be problematic. The expectation was that the effect of the denser bone would carry through to benefit the cow's plasma Ca, P, and Mg status at parturition. Prior to the period of K supplementation, the cows were part of a commercial pasture-based herd, to which they were returned at the end of the supplementation period and treated as 1 group from at least 11 d prepartum until the end of the study at d 42 of the next lactation. Supplementation with K successfully induced a sustained increase of urinary pH throughout late lactation and into the dry period, as expected. The KS cows consistently averaged a urine pH 0.25+/-0.10 U higher than the controls. However, there was no significant effect of K supplementation on BMD, bone mineral concentrations, plasma osteocalcin, urinary deoxypyridinoline:creatinine plasma Ca, or plasma P concentrations during or immediately after the cessation of supplementation, nor where there any carryover effects during parturition or by d 42 of lactation. Instead, there was an unexpected decrease in the concentration of Mg in plasma of the KS cows compared with the control cows that extended from 0.5 to 2.5 d postpartum. The timing of the decline in plasma Mg was paralleled by declines in plasma concentrations of 1,25 dihydroxy-vitamin D(3) and urinary excretion of Ca and Mg, whereas urinary excretion of P increased; all changes were consistent with a hypomagnesemia that could increase the risk of hypocalcemia. These data suggest that, in addition to the well-documented negative effects of K when fed immediately at parturition, the effects of high dietary K diets can carry over for at least 11 d to trigger a mild hypomagnesemia at parturition. Because K supplementation did not improve BMD prepartum, it was not possible to conclude for or against an ability of denser bone to reduce the risk of hypocalcemia in older cows at parturition. |
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Authors:
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M S Bhanugopan; W J Fulkerson; D R Fraser; M Hyde; D M McNeill |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: Journal of dairy science Volume: 93 ISSN: 1525-3198 ISO Abbreviation: J. Dairy Sci. Publication Date: 2010 May |
Date Detail:
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Created Date: 2010-04-23 Completed Date: 2010-10-20 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 2985126R Medline TA: J Dairy Sci Country: United States |
Other Details:
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Languages: eng Pagination: 2119-29 Citation Subset: IM |
Copyright Information:
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Copyright 2010 American Dairy Science Association. Published by Elsevier Inc. All rights reserved. |
Affiliation:
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Faculty of Veterinary Science, University of Sydney, NSW 2570, Australia. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Animals Body Constitution / drug effects Body Weight / drug effects Bone Density / drug effects* Bone Density Conservation Agents / administration & dosage, pharmacology Calcium / metabolism* Cattle Dairying Diet / veterinary* Dietary Supplements* Female Homeostasis / physiology* Parturition / physiology* Potassium, Dietary* / administration & dosage, pharmacology Pregnancy Random Allocation |
| Chemical | |
Reg. No./Substance:
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0/Bone Density Conservation Agents; 0/Potassium, Dietary; 7440-70-2/Calcium |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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