Grass tetany: With temperatures dropping, heavy showers and a recent surge in growth, grass tetany has been an issue on some farms over the last few days. Grass tetany, or hypomagnesaemia, is caused by a deficiency of magnesium (Mg) in the blood. Sucklers don’t have much ability to store Mg in their bodies and need a daily supply to prevent deficiency. It is common with suckler cows when they are grazing very bare, as well as lush pastures. This grass is frequently low in Mg due to quick growth and heavy slurry spreading, which is high in potassium and can have a negative effect on Mg uptake. It can be associated with stress like transport, wet weather, cows in heat or changes in diet or pasture. Ways of controlling or preventing grass tetany include:

  • Feeding high-Mg concentrates.
  • The addition of Mg to the drinking water (this can be questionable in periods of wet weather).
  • Buffer feeding with hay or straw.
  • Giving free access to high-Mg minerals, either by way of powder mineral or mineral licks.
  • The use of Mg bullets — at least two bullets/boluses should be used per cow which will release Mg at a controlled rate each day for four to six weeks.
  • BDGP update: Participants in the programme using a stock bull were required to have at least one bull on their holding on 30 June 2020 who was a minimum of 12 months old and was rated at four or five stars on the replacement and/or terminal index, within and/or across breed on the first genomic evaluation or the genomic evaluation at the time of purchase. There have been two simpifications: