Grass tetany, also known as grass staggers, is a metabolic disorder caused by low levels of magnesium in the blood. This condition is most common in lactating cows grazing lush cool-season grasses in early spring. Without timely intervention, grass tetany can be fatal, making prevention and early detection critical for cattle producers.
Causes and Risk Factors
Grass tetany is primarily linked to magnesium deficiency, but other factors also contribute:
- Pasture Composition: Early spring grasses, such as tall fescue, are high in energy and protein but often low in magnesium. Additionally, excessive potassium in these grasses can interfere with magnesium absorption.
- Environmental Stressors: Frost, drought, and other environmental changes can alter forage mineral balance, increasing the risk of grass tetany.
- Lactation Demands: Spring-calving cows have high magnesium requirements, and their reserves can be quickly depleted.
Recognizing Symptoms
Early detection can mean the difference between saving or losing an animal. Symptoms include:
- Increased excitability
- Teeth grinding
- Excessive salivation
- Muscle spasms
- Loss of body control
- Collapse and death in severe cases
Without immediate intervention, an affected cow may die within hours.
The Role of Potassium and Sodium
Research suggests that potassium and sodium levels in forage play a crucial role in magnesium absorption:
- Potassium Overload: High potassium levels in pastures can prevent magnesium absorption, even when forage magnesium levels appear adequate. Excess potassium often results from heavy fertilization in early spring.
- Sodium Deficiency: Sodium helps transport magnesium across the rumen wall. Freeze-damaged grasses often lose sodium, further reducing magnesium uptake. Providing free-choice salt or increasing salt levels in mineral supplements can support magnesium absorption.
The Importance of Phosphorus
Soil phosphorus levels also affect magnesium availability. Research indicates that maintaining adequate phosphorus levels in pastures can improve forage magnesium content, helping prevent grass tetany.
Prevention Strategies
Effective prevention requires a multi-faceted approach:
- Provide High-Magnesium Supplements: Use “hi-mag” mineral supplements containing 6%-10% magnesium, especially in early spring.
- Increase Salt Intake: Choose mineral mixes with 30% salt or mix additional salt into mineral supplements.
- Manage Fertilization: Avoid excessive potassium fertilization in early spring to prevent magnesium suppression.
- Graze Mixed Pastures: Introduce legumes like clover, which have higher magnesium content than grasses.
By understanding the interplay between magnesium, potassium, and sodium in forage systems, cattle producers can develop effective prevention strategies to minimize the impact of grass tetany and safeguard herd health.
