A mystery dairy cow illness which struck milking herds in the southwest of the country this spring was likely subacute or acute ruminal acidosis, according to the Department of Agriculture.

A Department spokesperson said “all available evidence” indicates that the cows’ symptoms of diarrhoea and a sudden drop in milk yield are down to this “metabolic condition associated with the transition from housed diets to lush spring pasture”.

Furthermore, it suggested that the illness is now an annual occurrence in late April and May in Cork and Kerry dairy herds which are grazing strong grass.

Observations

The Department explained that its Cork regional veterinary lab (RVL) has, since April, been receiving reports of herds affected by ruminal acidosis from vets on the ground dealing with farmers in Kerry, mid-west Cork, north Cork and east Cork.

“Affected cows typically have a slight or moderate reduction in appetite, loose faecal consistency, and sometimes reduced rumination, but they do not have a fever. The most consistent sign, and the main concern, is a sudden drop in milk yield,” it said.

The Department said that most affected cows remain “clinically well” with the ruminal acidosis with milk yields recovering within a week.

Food safety

It also confirmed that the syndrome has no implications for food safety.

On cow recovery, the spokesperson said farmers should feed cows silage for a part of each day or for a few consecutive days or provide the herd with access to straw.

“Occasionally, rumen buffers and other nutritional supplements are recommended,” they said.

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Mystery illness hits southern dairy herds