Factors Influencing Magnesium Absorption and Metabolism in Ruminants

Fontenot, J. P.; Allen, V. G.; Bunce, G. E.; Goff, Jesse P.

doi:10.2527/jas1989.67123445x

Cited by 61 publications

(36 citation statements)

References 56 publications

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“…Hence, differences in serum Mg can be attributed to this increased Mg intake, which was even twofold in the HD treatment. Blood Mg is not hormonally regulated to a constant level, but it is strongly affected by Ca regulation (Fontenot et al, 1989). In the current study, no differences were observed for Ca homeostasis indicators between treatments, so most likely the effects observed on Mg are due to differences in Mg supply.…”

Section: Discussionmentioning

confidence: 99%

Effect of feeding rumen-protected rice bran on mineral status of non-lactating dairy heifers

Martín-Tereso

Distefano

Laar

et al. 2010

Journal of Animal Physiology and Animal Nutrition

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Adapting Ca homeostasis of dairy cows before calving can prevent milk fever. Rice bran, treated with formaldehyde to prevent ruminal degradation of phytic acid, was fed to heifers to study its effect on Ca homeostasis. For 3 weeks 18 heifers were supplemented 3 kg of two feeds: placebo (PF) and rice bran (RBF), defining three treatments: control (CRT), low dose (LD) and high dose (HD). In weeks 1 and 3, all animals received 3 kg of PF and in week 2: CRT received 3 kg of PF, LD received 1.5 kg of PF and 1.5 kg of RBF and HD received 3 kg of RBF. Treatments did not affect dry matter intake (DMI). Feed intakes and growth rates indicated that all heifers had nutritional requirements that exceeded their Ca intakes. Serum Ca, urinary Ca, calcitriol or hydroxyproline remained unaffected. Urinary Ca was consistently low indicating high renal Ca reabsorption, which is indicative of insufficient Ca supply. Rice bran feed influenced P, Mg and Zn intakes and serum and urine presence of these minerals. Most heifers already presented an upregulated Ca metabolism, being inadequate to study adaptive changes in Ca homeostasis of multiparous dry cows. This metabolic difference can be explanatory to the very low susceptibility of heifers to milk fever, further supporting the induction of homeostatic adaptation before calving to prevent milk fever. Rice bran feed did not reduce DMI, and was not detrimental to P, Mg or Zn status.

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Section: Discussionmentioning

confidence: 99%

Effect of feeding rumen-protected rice bran on mineral status of non-lactating dairy heifers

Martín-Tereso

Distefano

Laar

et al. 2010

Journal of Animal Physiology and Animal Nutrition

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“…However, if influx is smaller than efflux, the relatively large Mg pools in the ICS or bones in a cow cannot acutely be mobilized to maintain physiological plasma Mg concentrations. Significant mobilization of Mg from bone appears to be unlikely because the ratio between Ca and Mg in bone is 42 to 1, and substantial withdrawal from bone would disrupt both Ca and pH homoeostasis (Fontenot, Allen, Bunce, & Goff, ). Furthermore, Mg absorption from the rumen is neither increased at hypomagnesemia (Martens & Stössel, ) nor stimulated by intravenous injection of PTH (parathyroid hormone) or PTHrP (parathyroid hormone‐related peptide; Dua, Leonhard, Martens, Abbas, & Care, ).…”

Section: Principles Of Mg Metabolismmentioning

confidence: 99%

Assessment of magnesium intake according to requirement in dairy cows

Martens

Stumpff

2019

Animal Physiology Nutrition

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To date, no specific hormonal regulation system has been identified for homoeostatic control of the essential mineral Mg. In cattle, the maintenance of physiological plasma Mg concentration depends on gastrointestinal absorption, primarily from the rumen, which serves as a pool for covering the requirement. Whereas a possible surplus (absorption greater than requirement) is rapidly excreted by the kidneys, a shortage (absorption lower than requirement) cannot be compensated for by mobilization from the large Mg pool in bones or soft tissue, so that the maintenance of the necessary physiological Mg concentration in plasma relies on continuous and sufficient absorption. Our knowledge concerning the site and mechanisms of Mg absorption has improved during the last few decades, and meta‐analyses of the absorption of Mg in dairy cows have shown that the K content has a pronounced negative effect on Mg digestibility. The current recommendations of Mg intake propose a constant percentage of Mg and emphasize the depressive effect of high potassium (K) intake on Mg absorption. The current knowledge about the antagonism between K intake and Mg absorption allows a more flexible solution which includes the K content of the diet. An assessment of Mg intake is proposed that incorporates the improved knowledge of Mg absorption, metabolism and requirement. Within this framework, an equation is derived that allows a prediction of the amount of Mg required to compensate for dietary K content, the goal being to avoid both possible undernutrition or an unnecessary surplus of dietary Mg.

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“…The nitrate concentration of pasture herbage is also elevated after N fertilizer is applied, and is generally higher in grass than in mixed swards (Papadopoulos etal. 1993 (Mayland and Wilkinson 1989), increasing the risk of hypomagnesemia (Fontenot et al 1989). The hypomagnesemia and high intake of K may also affect Ca metabolism in a way that could precipitate parturient hypocalcemia (Fredeen 1992 (Beede 1992 (Kunelius and Sanderson 1990 (Wilson 1975).…”

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confidence: 99%