“With this in mind, producers with cattle on pasture or planning their spring pasture turnout need to be aware of the possibility of grass tetany,” says Carl Dahlen, North Dakota State University Extension Service beef cattle specialist.
Grass tetany is caused by a magnesium deficiency. It’s most common when cows and ewes in heavy lactation graze lush spring growth. Rapidly growing forages have low levels of magnesium, and high levels of protein and potassium in the forage further reduce the availability of magnesium.
Animals with grass tetany may experience excitable and erratic behaviour, blindness, muscle tremors, a staggered walking pattern and, ultimately, death.
The onset of the condition can be very rapid, and the first symptom producers may see is a dead animal.
Forages most likely to induce grass tetany are cool-season grasses (crested wheat grass, bromegrass, bluegrass and timothy) and annual cereal grasses (wheat, rye, oats). Tetany also can occur in native range pastures when grass growth is rapid and lush.
Producers should consult their veterinarian about a treatment if they observe symptoms, Dahlen says.