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253. In many herds a culling rate of about 25% is normal. A distinction must be made between voluntary culling for genetic and economic progress, and involuntary culling, as a result of infertility and other problems. Poor fertility is the single most important reason for culling, irrespective of the age of the animal. Infertility in itself may not be a specific welfare problem but, in some cases, reduced rate of reproductive success can be an indicator of poor welfare, resulting from, for example, metabolic stress. Other causes of infertility include various perinatal diseases, twinning, dystocia, retained afterbirth and endometritis.
254. There are widespread problems with oestrus detection and conception to first service. Many herds fall well below targets of 80% oestrus detection and 60% pregnancy rate to first service. Training and education are most important in achieving targets in these areas and veterinary help is likely to be necessary in implementing a planned breeding programme. Poor observation can lead to the unnecessary use of hormones and other drugs. This can result in poorer welfare for cattle.
255. Pregnancy rates can be reduced by the stress of poor winter housing conditions and also by the mixing of cows (with associated aggressive behaviour) leading to early foetal death and return to service.
256. Managers should ensure that stockmen are allowed sufficient time to monitor herd fertility so as to limit the unnecessary use of hormones or other treatments. Observation for oestrus is necessary at least three times a day, including once in late evening, each for a minimum of 20 minutes.
257. If culling for infertility is appreciably higher than the industry norm, practical training on oestrus detection and other management factors influencing fertility may be necessary.