There are multiple potential causes of abortion and the detection of abortions in a herd can vary significantly depending on the husbandry system and calving pattern. Therefore, the reported incidence of abortion at herd level also varies markedly. It has been suggested that an abortion rate of 5% or more in a herd should be considered an indication of an abortion problem.
- Causes of Abortion >
- Effects of Abortion >
- Diagnosis of Abortion >
- Treatment & Control of Abortion >
- Medication/Vaccination for Abortion >
Causes of Abortion
The causes of abortion can be classified as follows:
Infectious:
- Non-specific
- Specific
Miscellaneous:
- Drug-induced (prostaglandins)
- Insemination/intra-uterine infusion
- Trauma/stress (transport, noise, veterinary treatment etc.)
- High fever and endotoxins (toxic plants, nitrate/nitrite, fungal toxins, other disease)
- Nutritional (malnutrition, vitamin A/selenium/vitamin E deficiency, goitre)
- Twin pregnancy
- Genetic (malformation)
- Hypothyroidism
Infectious causes of abortion tend to be more significant, both within herds and in terms of national disease status. Both non-specific and specific infectious causes of abortion can lead to "abortion storms" in a herd (i.e. where the incidence is >5%), whereas the miscellaneous causes often result in sporadic, individual cases.
The most important infectious abortion agents are listed below. It is important to note that several of these are also zoonotic:
- Neospora caninum abortion
- Salmonellosis (particularly Salmonella dublin)
- Leptospirosis
- Bovine Viral Diarrhoea (BVD)
- Listeriosis
- Infectious Bovine Rhinotracheitis (IBR)
- Campylobacteriosis
- Fungal/mycotic abortion
- Epizootic/chlamydial abortion
- Trichomoniasis
- Brucellosis
Effects of Abortion
Loss of calf or foetus
Diagnosis of Abortion
Loss of calf before 271 days of pregnancy
Treatment & Control of Abortion
Due to the multifactorial aetiology of abortions in cattle, general prevention of non-infectious abortion concentrates on good husbandry, feeding and management. The control of infectious abortion is based on good disease control through closed herd policy, careful screening and quarantine of bought-in or introduced (e.g. rented bulls) animals and good biosecurity. Specific control measures for individual infectious abortive agents are presented under each disease.
Once a sporadic abortion or an outbreak of abortions has happened, it is, in most cases, difficult to prevent further abortions from occurring unless the causative agent is identified and can be eradicated. In some cases, like IBR, further abortions will occur months after the first event.
An important cornerstone of abortion control in a cattle herd is good record-keeping of abortion events, and identification, if possible, of the causes in each detected case of abortion. It is, therefore, good practice to investigate all abortions, even though only about one third of all laboratory investigations of abortions produce a conclusive result. Over a period of time, a picture of the herd’s health status will emerge, and can be used to refine the Herd Health Plan to control disease.
A systemic examination of all abortion cases should be carried out by a veterinary surgeon who will collect information on the history of the individual cow and the herd, examine the cow and the foetus (including placenta), collect laboratory samples and interpret results in connection with the cow and herd history. In some cases, samples will need to be taken as part of statutory disease control measures, therefore, allabortions should be reported to the farm’s veterinary surgeon.
As it is virtually impossible to prevent an abortion from happening once the expulsion of a foetus has began, the treatment should concentrate on making sure that the dam does not suffer any long-term effects from the event. Subsequent retained foetal membranes or metritis need to be attended to.
In the case of an unknown cause, further spread of a potential contagious infection should be prevented by isolating the affected cow/cows, until discharges have cleared and/or until advised by a veterinary surgeon.
Medication/Vaccination for Abortion
The dam should be observed and treated if after-effects are seen. Affected animals should be isolated to prevent further spread.
To prevent abortions from happening or abortive agents from entering the herd, the following points should be included in the Herd Health Plan:
- Establish a closed herd policy where possible.
- If buying in stock, obtain from an accredited health status herd Screen and isolate bought-in animals for abortive agents such as IBR, BVD and Leptospirosis.
- Establish good biosecurity on the farm.
- Establish a good recording system for abortions on the farm (date, cow, stage of gestation, additional information, results of systemic examination by a vet).
- Report all cases of abortion in the herd.
- Undertake a disease investigation if the annual incidence is more than 4% (4 cows in 100).
See also:
This info was adapted from Defra’s Compendium of Animal Health & Welfare in Organic Farming, which is a collaborative effort led by Duchy College, Cornwall with VEERU at The University of Reading and The Faculty of Veterinary Medicine, University of Glasgow.
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