We all know the risks associated with introducing cattle to lush, rapidly growing pasture - that is Nitrate poisoning. Generally this occurs in autumn/winter on lush rapidly growing pasture such as fast growing annual ryegrasses or nitrogen/urea boosted pasture grazed too early and during dull, overcast, warm weather.

The secret is to introduce this sort of pasture gradually, feed in short periods, supplement with other feeds and watch for signs of sick cattle.

Well, here’s another reason to take care with new or lush pasture:

“Fog Fever”; also known as Atypical Interstitial Pneumonia, this condition has been diagnosed recently in our area, resulting in the sudden death of three cows.

Typically this condition is seen in the autumn when cattle are moved on to new lush pasture from drier more mature pasture. The reason we’ve seen it earlier than usual (one case before Xmas) is due to the dry pre-Xmas conditions followed by rain and sudden grass growth. Often the pasture concerned has been top-dressed with a nitrogenous fertiliser and the condition is generally seen within a couple of weeks of entry to the new pasture.

The syndrome is thought to be an allergic reaction to a breakdown product of an amino acid called L-tryptophan, which is present in pasture, especially lush rapidly growing pasture.

 

Clinical signs: Onset is normally sudden, with one or more animals affected. Symptoms can vary widely and the farmer may only notice one to be ill at the start. Severe breathing difficulty with loud grunts and frothy mouth breathing become obvious in acute cases but actual coughing is only heard occasionally. Mortality rates are often high (75%) but fortunately usually only a small number of cows are affected (5%). Sometimes cows are simply found dead in the paddock.

 

Treatment: in early cases, antihistamines and anti-inflammatories can help and antibiotics are often given to prevent a subsequent bacterial pneumonia. Remaining animals should be removed from suspect pasture (slowly, because stress and excitement can precipitate death). They can be safely returned to the same pasture after 2-3 weeks when the critical stage of growth has passed and grazing will be safe again.

 

Another reason to treat new, lush pasture with caution and respect when feeding to stock.