Grass Tetany in cattle or hypomagnesemia tetany is a highly fatal disease caused by excessive low magnesium levels in the blood. The grass becomes lush and green during the spring. Young grasses are low in magnesium. If you feed your cattle lush grass, there is a chance of grass tetany. Magnesium is a trace mineral in bone and is available in blood from bone and intestine. The low level of magnesium in the blood causes impaired nerve function and death.
Importance of Grass Tetany in Cattle
Grass tetany is one of Australia’s leading causes of death in beef cattle. The condition is primarily seen in older cattle and calves on foot. The condition is mainly found in late autumn through the winter. Gaunt cattle and excessive fatty cattle are more susceptible to this condition.
Causes of Hypmagnesemic Tetany in Cow
The general and common causes of grass tetany in cows are:
- Low magnesium intake in the diet through feeding lush and green grass and cereals.
- Excessive excretion of magnesium through milk.
- Digestive disturbances due to sudden environmental changes.
- Excessive feeding of low magnesium-containing grass like lucerne and clover.
- Season of the year like late autumn to winter.
Predisposing Factors of Risk Factors
The predisposing factors of grass tetany in cattle are:
- Feeding lush grass in the winter season of the year.
- Grasses are grown in acidic and sandy soil.
- High-yielding dairy cows at their pick of lactation (6-8 weeks after lactation).
- High moisture-containing grass.
- Reduced absorption from rumen due to low sodium and high potassium and nitrogen content in the rumen.
- Fasting or low energy intake or sudden changes in feed.
- Lower salt and phosphorus in the diet.
- Stress due to transportation.
Clinical Signs of Grass Tetany in cattle
In many cases, the affected cattle with grass tetany were found dead without showing clinical signs. The early clinical signs of the condition are as follows:
- The animal becomes nervous and excitable.
- Muscle twitching.
- Staggering gait.
- Abnormal movement.
- Body tremor.
- Hyper behavior.
- Death of the animal.
Diagnosis of Hypomagnesemic Tetany in Cows
The condition is difficult to diagnose early as most animals die before showing any clinical signs. The standard methods of diagnosis of hypomagnesemic tetany are:
- Clinical history of low magnesium intake in the diet, high-yielding cows, winter season.
- Presence of pathognomic clinical signs like muscle twitching, staggering gait, and nervous signs.
- Determination of magnesium level in blood.
Differential Diagnosis of Grass Tetany
The disease has similar signs to the following diseases or conditions:
- Nitrate poisoning.
- Lead poisoning.
- Bovine Spongiform Encephalopathy (BSE).
- Staggering gait caused bt ryegrass toxicity.
Treatment of Grass Tetany in Cattle
The essential treatment is the restoration of magnesium levels in the blood. The procedures of magnesium restoration are as follows:
- IV injection of calcium and magnesium preparation.
- In acute cases, subcutaneous injection of magnesium solution.
- You can provide oral magnesium preparation to prevent the reoccurrence of the disease in the herd.
- Magnesium oxide powder in feed or pasture.
- Magnesium licking block.
- Magnesium sulfate or soluble magnesium salt in hay or silage.
- Magnesium salt is added to concentrate or pelleted feed.
Prevention and Control of Hypomagnesemic Tetany
The preventive measures are of three types; immediate, short term and long-term.
- Immediate Action:
- Eliminate factors that reduce the absorption of magnesium.
- Supplement of magnesium in the diet.
- Short-term Measures:
- Increase energy in the diet.
- Provide good quality hay and silage.
- Provide magnesium salt block to herd.
- Reduce stress in animals due to transportation and yarding.
- Long-Term Measures
- Correct the soil acidity of pasture or grassland with lime and dolomite (having magnesium).
- Apply phosphate fertilizer to pasture and fodder crops.
- Avoid clover to animals.
- Make a ration scale of lactation cow with at least 2 grams of magnesium per kg concentrate feed.
Concluding Remarks on Grass Tetany in Cattle
Grass tetany is an acute and highly fatal metabolic disease of healthy cattle. The disease is caused by a sudden fall in blood magnesium level due to poor quality feed, less absorption in the rumen, or excessive excretion through milk, urine, and feces. The affected cattle mostly died without showing any signs. The disease can be prevented by carefully managing feed, grass, soil, and the daily activities of farms.