Abortions can occur at any stage of pregnancy, although usually only mid to late-term aborted foetuses are big enough to be noticed.
What causes abortions in sheep?
- There are various causes, most of which are infections.
- The most common causes are toxoplasmosis, caused by a tiny parasite, and Campylobacter infection and other types of bacterial infection like salmonellosis.
- Toxoplasmosis is spread from the faeces of cats, which can excrete the eggs for a short time usually when they are kittens. Older cats don’t usually pose any risk to sheep, so don’t heed old wives’ tales about getting rid of farm cats to prevent toxoplasmosis.
- A sensible precaution against toxoplasmosis is not to feed hay to younger more susceptible pregnant ewes if it comes from barns where there may have been kittens. This hay can be fed to non-pregnant hoggets and can help them develop immunity for future years.
- Some types of salmonellosis cause abortion in ewes, and affected ewes will become very dull and may have severe diarrhoea. They will require veterinary treatment.
- Poor quality silage and baleage can contain bacteria (Listeria) that cause severe diarrhoea and abortion in ewes. Aborting ewes will require veterinary treatment.
Prevention - sheep
- There are effective vaccines available against toxoplasmosis and Campylobacter infection and Salmonella infections in sheep.
- Vaccination should be carried out well before mating or early in pregnancy.
- Don’t feed poor quality baleage or silage to pregnant ewes.
What causes abortions in cattle?
- In cattle, a tiny parasite called Neospora is one of the most common causes of abortion.
- It is thought that some dogs have a role in spreading the disease.
- Mouldy hay and silage can cause fungal abortions in cattle.
- If cows are hungry and eat fallen macrocarpa foliage this can trigger abortions too.
Prevention - cattle
- Don’t let dogs eat afterbirths (placentae) and aborted calves, and keep pasture clear of dog faeces as much as possible.
- Don’t feed mouldy hay or poor quality silage or baleage to pregnant cows.
- Prevent access to macrocarpa foliage if cows are likely to eat it, ie if they are hungry or bored.