With the lush grasses and changing temperatures of the spring, it’s easy for cases of grass tetany to appear quickly in your herd. Taking preventative measures when turning out your cattle for the season can help prevent severe economic repercussions.
Grass tetany, often referred to as grass staggers, results from a magnesium deficiency in the blood. The first symptom tends to be poor coordination, which can lead to staggering and cattle going down, hence the term grass staggers.
Older and lactating cows tend to be most susceptible to a deficiency, especially when grazing fresh green pastures in the spring. Mature animals are unable to efficiently mobilize and use magnesium from the bones, which is why younger animals won’t display symptoms as quickly.
The rumen’s role in absorption
Ruminant animals are not as efficient at absorbing magnesium compared to non-ruminants. The primary site of absorption in ruminants occurs in the rumen, compared to the small intestine in non-ruminants. Magnesium must be highly soluble in order to be absorbed in the rumen.
Magnesium is essential to cattle for the correct transmission of nerve pulses and for other energy-generating reactions in tissues.
The level of magnesium in the blood strictly depends on the amount obtained from the diet. Grass in the spring tends to have higher levels of potassium and nitrogen, and lower levels of magnesium and sodium. Extra potassium in the rumen makes it more difficult to absorb magnesium, but presence of sodium makes it easier.
Essentially, potassium blocks magnesium absorption in the rumen and sodium boosts it.
The ability and ease of magnesium to dissolve also depends on the rumen pH. A lower, more acidic pH dissolves magnesium easier whereas excess nitrogen consumption can increase rumen pH, making it harder to absorb magnesium.
Prevention
When there is a magnesium deficiency in the diet, the neuromuscular functions become impaired, which causes staggering, muscle convulsing, nervousness, and can even lead to death. Spring-calving cows are especially at risk because peak lactation calls for increased levels of magnesium, but levels are low in the season’s grass.
Feeding a mineral supplement high in magnesium during high-risk periods such as springtime will help prevent the majority of deficiencies. However, it is important not to feed a high magnesium supplement year-round as it can decrease consumption during the crucial periods.
Additionally, supplementing with white salt blocks can help increase magnesium absorption. Keep in mind though, too much salt can increase urination, and magnesium can be excreted through the urine.
If cows still aren’t consuming enough magnesium from supplements, limiting grazing for several hours or feeding them hay can help slow the rate of passage in the digestive tract and allow more time for magnesium absorption.
Cows require 20 grams of magnesium in their diet, or four ounces daily of a 15 percent mineral mix. Consistent intake is crucial for deficiency prevention, so be sure to keep mineral feeders filled.
If detected early enough, grass tetany is treatable. Keep a close eye on cattle after first turning them out onto green pasture and be sure to call the vet at the first sign of possible tetany. An IV solution of magnesium, calcium, and glucose can get the cow up and going again. But if left untreated, in a matter of hours the cow can die. — Anna Miller, WLJ correspondent
