What causes abortion in beef cows and heifers?

Abortion is a word that every suckler farmer hates to hear at this time of year. There are many reasons why cows and heifers ‘throw a calf’.

These range from a simple slip or fall in the yard or shed to pathogens infecting the pregnant cow or heifer. According to Teagasc, any illness where a cow has a very high temperature can result in abortion.

Aborting cows do not normally display signs of illness unless there is retention of the foetal membranes (afterbirth). Illness that occurs at the later stages of pregnancy can result in abortion or stillbirths.

Individual or abrupt abortions may be caused by an infectious disease or a simple injury during pregnancy.

Any infectious pathogens that come into contact with the placenta in the pregnant cow/heifer and that cause damage to the foetus and/or the placenta can result in abortions.

When infection occurs – in early pregnancy – the resulting embryo loss may only be apparent when cows are found to be ’empty’.

Several abortions occurring within a relatively short period of time may indicate that multiple cows in the herd have been exposed to an abortion-causing infectious disease.

Infectious diseases

Brucellosis

This is a very contagious disease and is notifiable (required by law to be reported to government authorities). Abortion normally occurs after the first five months of pregnancy.

The placenta and fluids released at calving are highly infectious. Farmers are legally obliged to have any cow or heifer that aborts tested twice for brucellosis.

Leptospirosis

Leptospirosis can cause abortion at any time during pregnancy and is among the main causes of reproductive losses in Irish suckler herds.

It must be noted that tests on the aborted foetus are unsatisfactory and blood testing is required to confirm the disease. Vaccination should be carried out to ensure the herd is free from the disease.

Salmonellosis

This is a contagious disease which can cause abortions from the fourth month of pregnancy. It can also cause other illnesses in the herd. It can be detected from the aborted foetus or placenta or by blood test.

This disease can be difficult to control, as many animals can carry the organism without showing signs. However, salmonellosis is an exception where many of the aborting animals can sometimes show signs of illness.

Vaccination of the herd should be carried out if the disease is confirmed.

Neosporosis

Neosporosis in cattle is caused by a parasite found in the faeces of infected dogs or foxes. Abortion normally occurs between three and eight months of the pregnancy.

Infection from dogs can lead to multiple abortions within the herd. Once infected, animals remain infected for life.

Any live, full-term calves they produce may be born infected; allowing neospora to be passed from generation to generation. It can be detected in the foetus or in blood from the cow or heifer.

There is no vaccine available. Farmers should restrict the access of pets and wildlife to animals’ feed and remove infected animals from the breeding herd.

Mycotic abortion

Mycotic abortion is caused by a fungus that is normally found on poorly preserved silage.

Abrupt abortion normally occurs between month three and seven of pregnancy. In addition, the disease can be obtained from bedding. However, risk of infection from this source is low.

Listeria and bacillus are other bacteria which are also found in silage. These bacteria are common in preserved silage where soil has been picked up during harvesting.

Bovine viral diarrhoea (BVD)

BVD can cause a range of problems in suckler herds, including abortion. BVD-related abortion can occur at any stage of the pregnancy. However, it is more common in the early stages.

Tissue tagging of the foetus is a good way to check whether BVD has caused the abortion and all farmers in Ireland are required to carry out this practice.

Farmers should eliminate persistently infected (PI) animals from the herd, as these animals are a source of infection. This is the basis of the current Animal Health Ireland (AHI) eradication programme.

Vaccination can be used to protect the herd. However, the vaccination is not effective if PI animals are not removed.

Infectious bovine rhinotracheitis (IBR)

IBR can be transmitted by the semen of infected bulls. IBR is a form of virus pneumonia on Irish farms. It is also a cause of abortion in beef herds.

It is a very contagious disease and can spread from animal to animal rapidly. The disease can be passed from the mother to the calf and from one calf to another.

The disease is controlled when a strict vaccination programme is implemented.

Treatment and prevention

Any animal that has suffered an abortion, Teagasc says, should be quarantined – especially from other pregnant cows for two-to-three weeks until vaginal discharge has ceased.

Samples should be taken and sent for laboratory testing. Good hygienic practices should also be implemented; especially when handling the products of an abortion and any discharge from the aborting cow/heifer.

Diseases which cause abortions in cattle can also cause severe illness in humans.

Any contaminated material – such as afterbirth – should be disposed of hygienically. Pens where aborting animals have been housed should be thoroughly cleaned and disinfected.

Farmers should keep a close eye on other pregnant cows/heifers. Where vaccinations are available (BVD, leptospirosis, salmonellosis, IBR), programmes should be implemented to prevent re-occurrence of abortion.

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