“A Pinch of Salt”
by Chris Reinhardt, feedlot specialist
For ranchers who live in areas where grass tetany is common, the fear of suddenly losing a good cow and prevention planning is a normal part of the ranching calendar.
Grass tetany, often referred to as “grass staggers”, causes cows to become highly agitated, develop a staggering gait, collapse, convulse, and, ultimately, die. Grass tetany is caused by insufficient magnesium in the blood stream. This deficiency is normally caused by a combination of low magnesium in forages coupled with elevated potassium in forages. The elevated potassium hinders absorption of magnesium in the animal.
This combination of nutritional circumstances occurs most commonly in the spring of the year, while cows (most often lactating) are grazing cool-season pastures, when abundant moisture and warm temperatures result in rapid, lush, growth of pasture grasses. Grass tetany is most commonly observed in cows grazing cool-season forages in the spring of the year; however, it also has been reported in cows grazing small grain pastures. It can also happen during the fall and winter months if there is a magnesium deficiency or excessive potassium.
Fortunately, if caught during the early stages, grass tetany can be successfully treated. Unfortunately, however, we often do not observe the symptoms until it is too late. Therefore, knowledge is power, and we know when cows are most likely at risk and can prepare our herd for this potentially deadly issue.
The most common grass tetany prevention practice is to provide cows with a free-choice mineral mix with an elevated level of magnesium (8-12% is commonly recommended), starting 2-3 weeks prior to the lush growing season. However, the elevated magnesium, along with the lush grazing conditions, often results in poor palatability and limited intake of high-magnesium mineral mixes. Therefore, producers should encourage consumption by placing mineral feeders near water sources.
In addition, because magnesium absorption by the animal is actually dependent on the animal having adequate available sodium, it is essential that cows have access to free-choice loose salt during this same time frame. Place salt near water sources to encourage consumption, and to ensure that abundant good, clean water is available in conjunction with the elevated salt intake.
For best results, provide a high-magnesium free-choice mineral, in conjunction with a separate source of loose, free-choice salt, both placed near a quality, abundant water source, shortly before and during any periods of lush grass growth, particularly if cows are grazing predominantly cool-season forages.