Volume 12: Livestock Farming
5. Breeding programmes and techniques
Relevant aspects of pregnancy and calving

5.40 The gestation period of a cow is approximately nine months. Pregnancy may not go to its full term for a number of reasons. It is estimated that about 8 per cent of fertilised ova fail to develop because of some genetic defect or incompatibility between sperm and ovum. Foetal death between 25 and 30 days of pregnancy is common, and in most cases the foetus is absorbed into the uterine tissues. ¹

5.41 Abortion of the foetus also occurs. Brucellosis used to be the main cause of abortion in cattle. Since its eradication in 1985, abortions have accounted for only about 2 per cent of all calvings. ²

5.42 After calving, cows normally expel the afterbirth in a single piece within six hours. In a minority of cases, detachment can take up to seven days. ³

5.43 If left to its own devices, it is common for the cow to eat its own afterbirth. ⁴ Before the advent of BSE, an afterbirth was sometimes 'put out with the muck' and treated as compostable material, or left in the field, giving badgers and foxes access to it. A cow will not eat afterbirth that is not its own. ⁵

5.44 In response to the BSE epidemic, MAFF provided health and safety advice to farmers on precautions to take when assisting with calving. This included guidance on minimising the risk of transmission of BSE from cow to farmer via the placenta (see vol. 6: Human Health, 1989-96).