Grass tetany, a magnesium (Mg) deficiency in grazing ruminants, often
occurs simultaneously with periods of reduced solar radiation levels. The objective of
this study was to determine if reduced radiation levels produce a chemical composition
in grass indicative of a tetany-prone forage. Two grass species were exposed to three
radiation levels (8, 25, and 100% of actual) by shading with burlap cloth. The vegetatively
growing forage was harvested at weekly intervals over a 5-week period during
early spring.
Shaded forage had higher concentrations of Mg than did unshaded forage. However,
shaded forage compared to forage grown in full sunlight would likely result in less Mg
being available to the animal. The hypothesized inverse relationship between radiation
and the incidence of grass tetany in Idaho, Nevada, and Utah is supported by field
observations
