Grass tetany is only one of several diseases that can lead to sudden death on dairy and suckler farms during the spring months, according to Co Meath vet Frank O’Sullivan.

“Acute metritis and mastitis are equally likely to result in no warning mortalities on farms with freshly calved dairy and suckler stock at this time of the year,” he said.

But the veterinarian, on staff with Trim-based Patrick Farrelly and Partners, did confirm that the coming weeks represent the period of the year when spring calving dairy cows are most predisposed to grass staggers

“Tetany, or staggers, is caused by a magnesium deficiency,” he said.

“It is a mineral which ruminant animals cannot store with the result that they must secure the Magnesium they need in dietary form on a daily basis. During the month of April fast growing grass can be lacking in the mineral. Adding to cows’ predisposition to tetany is the impact of widely fluctuating weather conditions, particularly during those periods when warm days are followed by cold, frosty nights.”

O’Sullivan pointed out that dietary supplementation plus adding magnesium sources to drinking water supplies are effective means of preventing grass staggers.

“Magnesium boluses and dusting swards with CalMag are also effective,” he said.

“One possible downside of adding magnesium to drinking water during spells of wet weather is that the stock may be able to get most of the water they need from puddles in fields. Magnesium is also quite unpalatable.

“Mature cows need 30g of magnesium per head per day. If the mineral is included in concentrates be, the farmer must discuss the inclusion rates of magnesium required with his feed compounder.

“Dairy cows are more predisposed to tetany than suckler cows at this time of the year. The reverse is the case during the autumn months, which coincides with the associated stress of weaning for sucklers.