Effects of low sodium intake on magnesium metabolism of sheep

Abstract

Three sheep, equipped with cannulae in the dorsal rumen sac, abomasum and ileum, were fed a low sodium diet of artifically dried young grass. Mean daily intake of sodium was 310 mg. The sheep were given daily supplements of 0 or 2'3 g sodium by an intraruminal infusion.The concentration of K in mixed saliva and ruminal fluid from the sheep not given sodium supplements increased and the concentration of Na decreased markedly. The changes in the ion concentrations were associated with an increase of the transmural potential difference across the ruminal epithelium.The altered ion concentrations of Na and K in the ruminal fluid and the increased potential difference were accompanied by a decrease in Mg absorption from the forestomachs. The apparent availability of Mg from the gastrointestinal tract decreased from 34-5 (sodium supplementation) to 22-3 (low sodium intake).It is suggested that a daily intake of Na of 310 mg did not cover the sodium requirement of these sheep and that a low sodium intake influences the absorption of Mg in a similar manner as it has been observed with a high K intake.The results are discussed in context of grass tetany in ruminants. It is suggested that an inadequate intake of sodium is an overlooked factor of the pathogenesis of this disease.

Assessments of Fodder Values of 3 Indigenous and 1 Exotic Woody Plant Species in the Highlands of Central Ethiopia

“…The content of Na in the foliage and flower bud was below the requirement, and Na is important to regulate osmotic pressure, acid-base, and water balance in animals' bodies. Low levels of Na in feeds affect absorption of Mg (Martens et al 1987). Common salt or local mineral sources such as mineral soil can improve the deficiency of Na in the foliage and flower bud feed resources.…”

Research Note: Postnatal Development of Electrolyte Transport in Calf Rumen as Affected by Weaning Time

“…Due to different dietary electrolyte intake, rumen fluid osmolality is commonly challenged by alternating Na + and Clconcentrations in a wide range (Bailey, 1961;Martens et al, 1987). Rumen fluid osmolality has been shown to act as an important factor in controlling food consumption (Rossi et al, 1998;Burgos et al, 2000).…”

Growth rate responses to magnesium or sodium supplements in lambs grazing dual-purpose wheats

“…For example, the consumption of 30 g salt/day (Experiment 4) would raise the effective dietary concentration of Na well above the daily Na requirement for lamb growth. However, there are also sound reasons for expecting a range of minerals, especially Mg, K and Na to infl uence the Mg content of plant tissue (Coventry et al, 1987) and the ruminal absorption of Mg by livestock (Martens et al, 1987;Berger, 1992).…”

“…Forage Mg content was positively but poorly related to forage Ca content (r 2 =0.171). The high K and low Na concentrations in the wheat forage are a cause for concern, because high K and low Na intakes result in a high K:Na ratio in rumen fl uid, which in turn greatly reduces Mg absorption from the rumen (Martens et al, 1987;SCA, 1990;Berger, 1992). Although high forage K can often also reduce forage Na content (see SCA, 1990), there was no relationship between forage K and forage Na in Experiments 1-4.…”

“…Although high forage K can often also reduce forage Na content (see SCA, 1990), there was no relationship between forage K and forage Na in Experiments 1-4. Martens et al (1987) reported a 55% increase in Mg absorption when sheep consuming a low-Na diet were supplemented with Na into the rumen. It follows that in sheep consuming high-K forage, supplementation with Na could lower rumen K:Na ratio and increase Mg absorption.…”