Soil Oxygen and Temperature Effect on Tetany Potential of Three Annual Forage Species¹

Abstract

Grass tetany, a metabolic disorder of cattle on pasture, has often been related to low Mg and high K levels, and high K/(Ca+Mg) equivalent ratios in forages. These forage mineral imbalances often occur during wet periods when soil O2 may be low. The effect of 2, 4, 8, 16, and 21% soil air O2, on Ca, Mg, and K contents of rye (Secale cereale L.), ryegrass (Lolium multiflorum Lam.), and arrowleaf clover (Trifolium vesiculosum Savi) was studied in the growth chamber at 22 C day air temperatures and 12 or 16 C night temperatures. Increasing soil O2, had little effect on Ca or Mg content of rye forage but increased K from 2 to 5%, and increased the K/(Ca+Mg) ratio to over 4. Uptake of K, Ca, and Mg was generally lower at 12 than at 16 C. Ryegrass forage, grown at increasing soil air O2, had higher K, Ca, and Mg contents. Concentrations of K, Ca, and Mg in ryegrass were lower at 12 than at 16 C. Magnesium levels at 2 to 16% soil O2 were below the critical level of 0.2% at 12 C air temperature. Soil O2 had little effect on the composition of arrowleaf clover forage, except for a small increase in K. These results indicated that ryegrass forages, grown on poorly‐drained soil would likely be more tetany‐prone than that grown on well‐drained soil. However, rye forage would be more tetany‐prone when grown on well‐drained soil. The high Mg levels of arrowleaf clover showed its value in balancing tetany‐prone grass forage when it is maintained in a pasture.

The influence of soil oxygen availability on yield and nutrient uptake (N, P, K, Ca, Mg, Na) by winter rye (Secale cereale)

“…Thus, the only significant alteration in mineral composition observed by us for mature rye plants subjected previously to 2-week oxygen stresses concerns potassium. The decrease in straw-K is in agreement with a K reduction in rye forage at low soil 02, reported by Elkins and Hoveland (1977), whereas Dechnik et al (1985) did not find such a reduction in the same winter rye variety, not even after 4 weeks of flooding. No change in grain-K was observed by us at low ODR values in any of the three study years.…”

“…Few papers report the response of rye to soil hypoxia. Elkins and Hoveland (1977) found that the concentration of K in rye forage decreased with reduced soil 0 2 while that of Ca and Mg did not change. Dechnik et al (1985) observed an increase in N and a decrease in P and Mg (without an effect on K and Ca) in winter rye grain and an increase in N, Ca and Mg in rye straw associated with up to four weeks of flooding at stem elongation.…”

Effects of magnesium supplements on the digestion of forages and milk production of cows with hypomagnesaemia

“…However, the Mg content was relatively low (16g/kgDM), possibly due to the waterlogged ground conditions pertaining during an exceptionally wet spring (Elkins and Hoveland, 1977). However, the Mg content was relatively low (16g/kgDM), possibly due to the waterlogged ground conditions pertaining during an exceptionally wet spring (Elkins and Hoveland, 1977).…”

Using Plant Breeding and Genetics to Overcome the Incidence of Grass Tetany

“…Soil 02 levels often are low during the grass tetany season because soils often are saturated with water. Elkins and Hoveland (1977) showed that low soil 0 2 levels caused a decrease in Mg concentration of annual ryegrass (Lolium multiflorum L.). Haaland et al (1978), in a greenhouse study, examined the effects of low soil 02 levels on Mg concentration in tall fescue and found similar results.…”