Cows can suffer abnormalities during pregnancy leading to death of the foetus or resulting from foetal or maternal abnormality. Abortion in dairy cattle is the loss of a foetus between the age of 42 days and approximately 260 days.
Pregnancies lost before 42 days are usually referred to as early embryonic deaths, whereas a calf that is born dead between 260 days and full term is definedas a stillbirth.
Causes of abortion in cows
There are multiple causes of abortion and the detection of abortions in a herd can vary significantly depending on the husbandry system and calving pattern, the incidence of abortion at herd level also varies markedly.
It has been suggested that an abortion rate of five per cent or more in a herd should be considered an indication of an abortion problem.
Abortion in cattle is caused by so many factors which are categorised into non-specific and specific abortion.
Non-specific include drug-induced, Insemination/intra uterine infusion, trauma or stress as a result of transport, noise, veterinary treatment among others.
Specific abortion causes include high fever and endotoxins such as toxic plants, nitrate, and fungal disease among other diseases.
Nutritional deficiency can also cause abortion and this includes malnutrition, deficiency of Vitamin A or E and selenium. Malformation of pregnancy or twin pregnancy can also lead to abortion.
Both non-specific and specific infectious causes of abortion can lead to abortion storms in a herd. The most important infectious abortion agents are Salmonellosis mainly Salmonella Dublin, Listeriosis among others.
Fungal abortion are associated with contaminated feed and are either sporadic or occur in small outbreaks, normally between the fifth and the seventh months of pregnancy. Epizootic abortion in cattle, caused by Chlamydia is an emerging cause of contagious abortion in cattle.
A low rate of abortions is usually observed on farms and three to five abortions per 100 pregnancies per year is often considered “normal. However, the loss of any pregnancy can represent a significant loss of potential income to the producer and appropriate action should therefore be taken to prevent abortions and to investigate the cause of abortions that may occur. Each abortion is estimated to cost the producer Shs40,000 to Shs80,000 depending on such factors as the current value of replacement stock, feed and milk prices, and the stage of gestation when the abortion occurs.
General prevention of non-infectious abortion concentrates on good husbandry, feeding and management. The control through closed herd policy, careful screening and quarantine of bought in or introduced or rented bulls and good bio-security.
Specific control measures for individual agents need to be known. A systemic examination of abortion cases should be carried out by a veterinary surgeon that will collect information on the history of the individual cow and the herds, examine the cow and the foetus including the placenta, collect laboratory samples and interpret results in connection with the cow and the herd history.
Although it is virtually impossible to prevent abortion from happening once the expulsion of a foetus has begun, the treatment should concentrate on making sure that the cow does not suffer any long term effect from the event.
In the case of unknown cause, further spread of a potential contagious infection should be prevented by isolating the affected cows.