With turnout being later than anticipated this year, now is the time to be thinking about prevention for cases of hypomagnesemia – more commonly known as ‘grass staggers’. Staggers usually affects recently calved beef cows; however dairy cows are also at risk writes Charlotte Phillips of Farm First Vets.

Magnesium (Mg) is not stored by the body therefore it needs to be administered daily to cattle during high-risk periods. These are periods with fast growing, lush pastures which are low in fibre. This increases the rate of transit time through the rumen, leaving less time for the magnesium to be absorbed, resulting in low levels.

Grass staggers is a neurological condition which may present as hyperexcitability, muscle spasms, respiratory distress or progress to collapse, seizures, and even sudden death. There may be evidence of soil disturbance around the recumbent cow suggesting seizure activity. Any cases seen should be treated as a veterinary emergency.

A minimum target intake for lactating suckler cows is 30g of magnesium, and for dry cows the level is 20g; which includes background levels from forage. In areas where potash levels are high (over 2%), then 40g should be the target for the total diet (30g for dry cows). High nitrogen levels in the grass are also thought to interfere with Mg absorption.

There are several ways to supplement cows with magnesium, so it should be possible to find a method to suit individual farms:

· Magnesium in the water- added as a soluble salt magnesium sulphate or chloride. This is available from local farm supply retailers and usually comes in builder-type cement bags. A small hole should be made in one side of the bag which is then dropped into the bottom of the water tank. This will slowly release magnesium into the water. For this method to work effectively, the drinking trough must be the only source of water available to the cattle out grazing.

· Pasture dusting with calcined magnesite. Grass should ideally be damp when applying so that the dust sticks to the leaf. This will last for 10 - 14 days, however reapplication is required after heavy rainfall.

· Magnesium lick buckets are commonly used as is a practical method for many farms and can be effective provided all the cows are taking them – individual uptake is not guaranteed, so some cows will still be at risk.

· Magnesium bolus – the number of boluses will vary depending on the product used and usually give about four weeks protection. The downside to this method is that it is labour-intensive, and boluses can be regurgitated in some cases.

· Supplementing the cows with extra forage at grass, such as hay, silage, or straw will help increase rate of magnesium absorption.

· High magnesium nuts – if you need to feed more than 1kg of nuts to get the required level of Mg it can become costly.

Note that anything which affects dry matter intake will impact the cows’ magnesium status, increasing the risk of grass staggers. A few examples of this would be rotational grazing, when aiming for a low target residual before changing to

a new paddock, harsh weather (cattle tend to shelter in field corners) and stress events such as calving and weaning.

If you have any questions about the risk of Staggers in your herd or any questions about animal health on your farm, please call Farm First Vets on 01873 840167.