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Managing a Period of High Grass Staggers Risk

18 October 2019

Across the country there has been a spike in the number of cases of Hypomagnesemia (grass staggers) in cattle.  Staggers is caused by cows having a lack of Magnesium and is often fatal to cows, impacting on both animal welfare and business profitability.

Below are a few simple steps to reduce the risk of staggers affecting your herd.

  1. Ensure that cows are eating enough so that they are not in negative energy balance and hence low magnesium and under additional metabolic stress. The less stress the better – extra care is needed when cows are handled and calves weaned.
  2. If grass is below 6 cm, cows must be supplemented for energy as well as for magnesium. This can be from silage, hay or straw. Remember straw is very poor for magnesium and low in energy. If spring-calved cows are eating more than 5 kg/head/day of straw while at grass, they are needing better forage to meet their needs.
  3. Avoid periods where intakes may be lower than required then suddenly change, for example, rotational grazing taking residuals too low to meet nutritional needs for the time of year, then moving to a lush paddock or overnight with no feed, then a move in the morning.
  4. Observe cow behaviour and spot the risk factors. For example, cows standing around the gate or sheltering from weather for long periods without eating. Look at the amount of grass available and if they are going to realistically meet their daily requirements from this grass.
  5. Always take into account the risk of magnesium shortage by checking the base ration the cows are on and what is being supplied by additional supplements.

In order to increase Magnesium level in the base diet, you may consider some of the following:

  1. Hi Mag rolls; normally 1 kg supplies a full daily Magnesium requirement (check with supplier). These are easy fed on the ground. 1 kg will also supply around 10 MJ of energy which is important when grass supplies are short.
  2. Mineralising your own cereals – this is cheaper but you need to account for wastage when feeding on the ground and possibility losing mineral on the ground – 100 g/head of a 25% magnesium mineral is required.
  3. Liquid molasses fortified with magnesium – harder to regulate intakes.
  4. Hi Mag buckets or free access mineral – aim for around 20% mag in buckets and 25% mag for powdered minerals. The downside is you are relying on all cows taking the minerals – ensure good access to minerals/enough buckets are put out for the number of cows.
  5. Where grass supplies are running low and cattle are beginning to poach, the best option may be to house cows and offer them a full winter ration.

Karen Stewart,

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