Crop Poisoning

Brassicas are most frequently grazed during summer and autumn and less frequently during winter.  They provide high quality feed for cows and young stock when pasture availability and quality is often low.  In addition they are a useful part of pasture renovation programs.  While many herds graze brassica crops without clinical disease problems, over recent years a number of diseases have been identified. Some of these incidents resulted in multiple deaths and substantial economic loss.

In the early grazing period cattle are at a greater risk of disease occurring.  This highlights the importance of careful grazing when cattle are first fed brassicas.

Signs commonly observed with crop poisoning include:

  • Cows with red painful udders or kicking at their bellies e.g. from photo
  • Staggering or down cows
  • Diarrhoea
  • Bloat
  • Choke
  • Redwater (red urine)
  • Jaundice (yellowing of the pigments around the face, vulva, etc)

If there are any signs of disease observed while the cattle are on the crop:

  • Remove the sick cow(s) or herd from crop.
  • Feed high quality hay or silage.
  • Continue feeding concentrates if scouring/staggering not caused by lactic acidosis (overload).
  • Contact veterinarian if necessary.


Some of the diseases associated with crop poisoning are easily cured / managed.

Photosensitization (Photo, Swamp fever, Fire fever)

  1. Feed grain and hay/silage.
  2. Inject with 5ml Histamil for 3 days if early, or while the skin is irritated if severe
  3. Restrict access to green feed until recovered.
  4. If possible provide shade.
  5. Other products which may be beneficial in a case of photo, include zinc creams, teat creams etc.

Photosensitization outbreaks were more likely when nitrogen-containing fertilisers were applied and when crop yields were low.

Scouring cows

The scouring may be caused by carbohydrate overload (lactic acidosis); excess amounts of green leafy feed or nitrate poisoning.

  • If you suspect carbohydrate overload as the cause, drench the cow with 2 cups of bicarb.
  • If the eyes are sunken (dehydrated), call a vet to administer IV fluids.


Keep a close watch on these cattle after treatment, as the signs may deteriorate quickly, especially if carbohydrate overload or nitrate poisoning is the cause.

Staggering and down cows

May be caused by milk fever, grass tetany, carbohydrate overload or nitrate / nitrite poisoning.  Nitrite poisoning may show signs of muscle tremor, it is important in these cases not to stress the cattle affected.

  • Give calcium subcutaneously or intravenously.
  • If no response and cow is down, call vet to distinguish between carbohydrate overload and nitrite poisoning.

Choke

The fodder (eg turnips) being stuck in the throat causes choke.  If complete blocking of the throat occurs the cattle will blow up rapidly because they can not belch to release rumen gases.

  • Call vet for assistance.
  • Stab only if the condition is life threatening.


Redwater


Requires veterinary attention as some cases may require a blood transfusion or other necessary treatment.



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