How will a mild wet winter affect lactating cows?

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Experts from Scotland’s Rural College (SRUC) have recently alerted farmers that due to a mild wet winter, the risk of staggers may be increased.

Although soil temperatures are expected to be a few degrees warmer than average at turn-out, the mild winter brought prolonged wet conditions, diluting grass dry matter (DM) content, and causing leaching of micro nutrition within grass.

David Thornton, Rumenco technical manager, explains how this can affect lactating cows: “Magnesium is a key requirement for lactating cows at grass, be it suckler or dairy cows, as with every litre of milk produced, magnesium is lost from the system. If cows have a magnesium deficiency, they are at risk of staggers, also known as hypomagnesaemia.

“For some, high potash levels will cause further problems, as potassium (K) which is the main component, locks up magnesium availability,” says David. “With magnesium not easily mobilised from stores in cows’ bodies, coupled with a low level of magnesium in circulation, they rely on a constant supply in their diet. These factors combine to make it hard for grazed diets to match demands.”

The average potassium (K) levels in spring grass can vary, and as K levels increase, more magnesium is required. Data captured from over the last 10 years shows that average K levels in grass for April are around 3.21%, meaning 40g/day of magnesium is required.