Magnesium metabolism and hypomagnesaemia

Martens, H.; Rayssiguier, Yves

doi:10.1007/978-94-011-8067-2_21

Cited by 57 publications

(54 citation statements)

References 42 publications

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“…Ammonia also interferes with ruminal Mg 21 absorption (Martens and Rayssiguier, 1980), with effects on both the electrogenic and the electroneutral component (S. LeonhardMarek and H. Martens, unpublished data (Goytain and Quamme, 2005;Kozak et al, 2005). It thus seems difficult to hypothesize mechanisms of adaptation that would explain why the effect of ammonia on ruminal Mg absorption disappears within some days as observed by Gä bel and Martens (1986).…”

Section: Absorption Of Ammoniamentioning

confidence: 93%

“…This interdependance explains the negative impact of high ruminal K 1 concentrations on Mg 21 absorption observed in vivo (e.g. Care et al, 1984;Grace et al, 1988) and in vitro (Martens et al, 1987;Leonhard-Marek and Martens, 1996) as well as part of the negative effects of NH 4 1 (Martens and Rayssiguier, 1980). The uptake of K 1 depolarizes the apical membrane potential and thus reduces the driving force for electrogenic uptake of Mg 21 (Leonhard-Marek and Martens, 1996).…”

Section: Absorption Of Magnesiummentioning

confidence: 99%

“…Although older studies have shown that Mg can be absorbed across all the three forestomach compartments (Martens and Rayssiguier, 1980), attempts to characterize the underlying mechanisms have only been performed with ruminal tissues. Within the rumen epithelium at least two mechanisms ensure an efficient Mg 21 uptake into RECs ( Figure 2).…”

Section: Absorption Of Magnesiummentioning

confidence: 99%

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Transport of cations and anions across forestomach epithelia: conclusions from in vitro studies

Leonhard-Marek

Stumpff

Martens

2010

Animal

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Secretion of saliva as well as absorptive and secretory processes across forestomach epithelia ensures an optimal environment for microbial digestion in the forestomachs. Daily salivary secretion of sodium (Na 1 ) exceeds the amount found in plasma by a factor of 2 to 3, while the secretion of bicarbonate (HCO 3 2 ) is 6 to 8 times higher than the amount of HCO 3 2 in the total extracellular space. This implies a need for efficient absorptive mechanisms across forestomach epithelia to allow for an early recycling. While Na 1 is absorbed from all forestomachs via Na 1 /H 1 exchange and a non-selective cation channel that shows increased conductance at low concentrations of Mg 21 , Ca 21 or H 1 in the luminal microclima and at low intracellular Mg 21 , HCO 3 2 is secreted by the rumen for the buffering of ingesta but absorbed by the omasum to prevent liberation of CO 2 in the abomasum. Fermentation provides short chain fatty acids and ammonia (NH 3 ) that have to be absorbed both to meet nutrient requirements and maintain ruminal homeostasis of pH and osmolarity. The rumen is an important location for the absorption of essential minerals such as Mg 21 from the diet. Other ions can be absorbed, if delivered in sufficient amounts (Ca 21 , P i , K 1 , Cl 2 and NH 4 1 ). Although the presence of transport mechanisms for these electrolytes has been described earlier, our knowledge about their nature, regulation and crosstalk has increased greatly in the last years. New transport pathways have recently been added to our picture of epithelial transport across rumen and omasum, including an apical non-selective cation conductance, a basolateral anion conductance, an apical H 1 -ATPase, differently expressed anion exchangers and monocarboxylate transporters.Keywords: ruminants, sodium potassium magnesium and calcium, short chain fatty acids, chloride and bicarbonate, channels transporters and exchangers ImplicationsThe improved knowledge of ruminal ion transport clearly underlines its physiological meaning for the whole animal. For example, magnesium absorption is markedly reduced at low Mg and high K intake and the effect of potassium is diminished at high Mg intake. This variable interaction has been quantified recently permitting the prediction of Mg absorption. Great progress has also been made in understanding the interactions between the absorptive pathways for Na, short chain fatty acids and ammonium. The new findings on structure and regulation of various ion transporters will allow a better understanding of the challenges that different diets pose to the maintenance of homeostatic conditions within the rumen and within the cells of the surrounding epithelium, with the implications for the investigation of ruminal adaptation to different diets. Future studies on transport pathways should include the barrier function of rumen epithelium and its possible impairment under harsh feeding conditions.

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Section: Absorption Of Ammoniamentioning

confidence: 93%

Section: Absorption Of Magnesiummentioning

confidence: 99%

Section: Absorption Of Magnesiummentioning

confidence: 99%

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Transport of cations and anions across forestomach epithelia: conclusions from in vitro studies

Leonhard-Marek

Stumpff

Martens

2010

Animal

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“…13, No. 4, OCTOBER 1991 " DISCUSSION An increased intake of dietary K depresses dietary magnesium availability in ruminants (10,17), and the recommended magnesium content in the dry matter may no longer be adequate when cows are fed grass or grass silage with high levels of K due to heavy fertilisation. In the present experiment the prepartal ration supplied the cows of the low-Mg groups with on average 20 g Mg/day, their ration contained 0.22% Mg in the dry matter.…”

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confidence: 99%

Effects of a deficient magnesium supply during the dry period on bone turnover of dairy cows at parturition

Mosel

Klooster

Wouterse

1991

Veterinary Quarterly

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SUMMARY. The bone activity and bone mineral content in rib bones resected from 33 dairy cows between 3 and 8 h after parturition were measured, and the effects upon them of a deficient supply of dietary magnesium (Mg) during the last seven weeks of pregnancy were studied. The cows were fed a diet containing either 0.22% magnesium (low Mg) or 0.82% magnesium (high Mg) in the dry matter (DM), and the potassium content of both rations was increased to approximately 4.1% in the DM to reduce the absorption of magnesium. In the cows fed the low-Mg diet a fall in plasma Mg concentration was observed In the low-Mg, low-parity cows the plasma Mg concentrations at parturition were higher than in the low-Mg, high-parity cows, i.e. 0.83 mmol/l and 0.54 mmo1/1, respectively. After parturition four cows in the lowMg, high-parity group showed clinical signs of hypocalcaemia but none of the other groups did so. The bone formation in low-parity cows was significantly (P < 0.05) affected by Mg supply, with higher percentages of both trabecular surface covered by osteoid and osteoid volume in the low-Mg group. In the high-parity cows no significant differences in bone formation were found between the low-and high-Mg groups. An inadequate Mg supply resulted in a significantly (P < 0.05) higher Ca content in the bone ash of low-parity cows and a significantly (P < 0.05) higher bone ash percentage in the bone of high-parity cows.

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“…The small number of cows used may explain why in our study there were no cases of tetany. Alternatively, it could be suggested that factors other than K in spring grass also play a role, such as N intake (5, 6, 9), Na intake (10, 17), trans-aconitate content of grass (28), content of rapidly fermentablable carbohydrates in grass (17), content of higher fatty acids in grass (11) dry matter intake, the water content of the ration (15), type of weather (24), and stress factors (16). ,…”

Section: Discussionmentioning

confidence: 99%

Time courses of plasma magnesium concentrations and urinary magnesium excretion in cows subjected to acute changes in potassium intake

Schonewille

Klooster

Wouterse

et al. 2000

Veterinary Quarterly

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Hypomagnesaemic tetany in cows develops occasionally after an acute increase in K intake such as can occur when cows are transferred to spring grass. There is evidence that under these conditions plasma Mg concentrations are only transiently decreased. In this study the questions addressed were whether the plasma Mg concentration, indeed adapts to a high K intake as only dietary variable, and whether urinary Mg excretion is associated with this adaptation. Dry cows were fed rations containing either 26 or 50 g K/kg dm, the extra K being in the form of KHCO3. When the cows were acutely transferred from the low to the high K ration, plasma Mg concentrations fell slightly, but significantly from 0.86 to 0.76 mmo1/1 within five days, but rose again to 0.80 mmo1/1 after another 23 days, this rise being also statistically significant. None of the animals developed tetany. The decrease in plasma Mg concentration in individual animals after five days on the high-K ration ranged from 6 to 21 %. The time course of urinary Mg excretion resembled that of plasma Mg concentration; minimum Mg excretion was seen after four to six days on the high-K ration with a subsequent increase thereafter. To explain the transient lowering of plasma Mg concentration, it is suggested that the K-induced decrease in Mg status caused a delayed increase in the carrier-mediated component of Mg absorption, which in turn caused an increase in urinary Mg excretion. When the cows were acutely switched from the high to the low K ration, plasma Mg concentration and urinary Mg excretion rose, but no transient changes were seen.

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Magnesium metabolism and hypomagnesaemia

Cited by 57 publications

References 42 publications

Transport of cations and anions across forestomach epithelia: conclusions from in vitro studies

Transport of cations and anions across forestomach epithelia: conclusions from in vitro studies

Effects of a deficient magnesium supply during the dry period on bone turnover of dairy cows at parturition

Time courses of plasma magnesium concentrations and urinary magnesium excretion in cows subjected to acute changes in potassium intake

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