Spring turn out is the highest risk period for hypomagnesemia, more commonly known as grass staggers. Ellie Layton looks at ways livestock farmers can reduce the risk.
Grass staggers is a metabolic disorder which affects cattle and on rare occasions, sheep, too explains Matt Foulkes, farm vet and owner of Black Mountains Farm Services based in Powys. He adds that although grass staggers is relatively uncommon, the mortality rate is high.
Grass staggers is seen when an animal does not receive their daily requirement for magnesium. He explains that magnesium is essential in many metabolic processes like protein synthesis and nerve function. Grazing animals cannot store or control blood magnesium levels, this means a constant supply is needed to maintain normal levels.
Availability of magnesium can be restricted by excess potassium and nitrogen levels in the soil and grasses. Interestingly, clover has a high magnesium content but its growth can be restricted where nitrogen levels are high, says Mr Foulkes.
Low dry matter content of spring grass contributes to the condition, with the lack of fibre content speeding up gut transit time, therefore reducing magnesium absorption.
Any factors that reduce grazing, like wet weather or tight grazing conditions, can cause stock to be vulnerable if not correctly supplemented.
Lactating cows, often four to eight weeks post calving, are most at risk. Older animals are susceptible as they are more likely to have greater ongoing losses in milk yield, explains Mr Foulkes.
The annual incidence of grass staggers in the UK is reported to be less than one per cent, with recently calved beef animals making up a large proportion of these cases.
When should you seek veterinary advice?
If the condition is suspected, you should contact a vet immediately. Grass staggers is one of the true veterinary emergencies, says Mr Foulkes.
Animals with this condition can be a serious health and safety risk, so it is vital to ensure yourself and others are not in danger when trying to treat an animal.
What can be done to reduce the risk?
Planning ahead of turnout can be one of the most effective ways to reduce the risk of grass staggers says Mr Foulkes
He adds that ensuring the correct dry cow mineral supplementation in the lead up to calving will help to regulate the release of calcium from bone, which will help reduce the risk of milk fever. He also advises trying to ensure that the dry cow supplement contains greater than 10 per cent magnesium and less than 14 per cent calcium. Forage analysis enables the calculation of more precise inclusion rates. Magnesium supplementation in the dry period results in fewer calvings that are slow to progress, due to its critical role in muscle contraction.
Mr Foulkes says: Getting animals used to any supplements is imperative before turnout. The palatability of magnesium salt is poor, so giving cattle a minimum of three weeks to adapt is important and will improve intake. When using complete dry cow mineral mixes, which also carry multiple other benefits, supplementation should begin four to six weeks before expected calving for maximum effect.
Buffer feeding with extra roughage such as hay or straw can be helpful to slowdown gut transit of fresh grass. Using a feeder can help, as stock can shelter by the feeder whilst eating.
Longer term strategies can include soil and forage analysis as well as fertiliser planning to avoid excess pasture application of potassium and/or nitrogen.
Can you test?
You can test for magnesium deficiency within the herd. This is normally done by blood testing a selection of five to 10 cows that are within a month or so of calving, says Mr Foulkes.
In 2019, a Scottish Government funded study found that one third of tested herds were low in magnesium pre-calving and one quarter deficient post-calving.
Blood testing can be a useful surveillance tool to check and correct ration formulation, as required.
What supplement options are on offer?
- Loose minerals (mixed with daily ration to increase palatability; buffer feeding after turnout facilitates their ongoing use)
- Boluses
- Magnesium cobs
- Water supplements (these must be in all available water sources to ensure adequate intakes from all animals)
- Lick buckets (Some cows may favour these leading to selective intake and variable results)
-Pasture dusting (every 10-14 days)
What are the clinical signs of grass staggers?
- High head carriage
- Twitching of muscles (especially around the head)
- Incoordination (staggering walk)
- Separation from the group
- Flighty behaviour
- Bulging of the eyes
- Teeth grinding
After this, an animal will often lay down and start exhibiting seizures with paddling of the legs, warns Mr Foulkes. Unfortunately, finding one or multiple animals dead, can often be the first sign.
