It can be disheartening when you see your cows slipping, especially after all the effort you put in over mating. 

The reality is, a certain number of slips are inevitable. But it’s still worthwhile keeping an eye on how many you have and trying to avoid those that can be managed out of the equation.  

So, what’s normal? It’s common to see about 2-5% of your cows abort, and another 3% may abort unseen.   

Some possible causes of abortions in cattle include:

• Nitrate poisoning. 

• Ingestion of toxic plants (especially Macrocarpa or any species of pine tree).

• Salmonella infection (not every strain causes abortions, but they do happen occasionally). 

• Bovine Viral Diarrhoea infection, which can cause anything from early embryonic loss and calf abortions, to calves being born ok but not thriving, depending on the stage of pregnancy the cow gets infected at. 

• Neospora caninum infection, which can cause an abortion or a mummified foetus. While dogs are commonly involved with the Neospora lifecycle, infected cows spreading the parasites and cow-to-cow transmission via aborted material are also ways the disease can be transmitted. 

• Consumption of bad quality silage – grass silage that’s been poorly preserved can grow the bacteria Listeria monocytogenes. Soil contamination in the silage, low dry matter content, or poor fermentation can all reduce the quality. While abortions are more usual after cows have recently eaten the bad silage, they can sometimes occur at a
  later date.

• Consumption of mouldy silage – eating mouldy silage or hay can cause fungal diseases such as Aspergillus fumigatus or Mortierella wolfii, which can trigger abortions. A fatal fungal pneumonia can follow after a Mortierella abortion.     

Essentially, any illness a cow gets while she is pregnant could potentially cause a slip, making it quite difficult to identify what the reason was.  

If you’d like to investigate, samples that can help your vet determine the cause of an abortion are: 

• The whole aborted foetus,

• The placenta,

• Blood from the cow.

Lab testing may not always be able to discover the cause of an abortion. Sometimes the material has already decomposed, and having positive antibodies for diseases like Bovine Viral Diarrhoea doesn’t necessarily mean it caused the abortion. 

However, if you’d like to give testing a go to try and find out the reason, make sure you keep the foetus and placenta cool until you can get it to us. 

If you think you’re having too many slips, talk to your vet.