Volume 12: Livestock Farming
11. Other livestock
Relevant aspects of UK sheep production
Structure of the industry
Sheep diet
Scrapie

Structure of the industry

11.2 Although there was an overall increase in the number of sheep and lambs in the UK between 1986 and 1995 (from 37 million on 85,000 holdings to 42.7 million on 82,800 holdings), sheep numbers actually peaked in 1992 at 44 million. Sheep numbers had grown steadily since 1980, when there were 31.5 million. ¹ This growth was mainly attributable to the introduction of the EU sheep meat regimein 1980, which resulted in the introduction of the Variable Premium Scheme inthe UK, and partly due to the imposition of milk quotas, which encouraged dairy farmers to diversify their operations.

11.3 There are about 40 native breeds of sheep and many crossbred sheep kept primarily for meat production, with wool an important secondary product. Throughout the period 1986-95 about 70 per cent of sheep farms also raised cattle, and the combined farms accounted for about 81 per cent of sheep and half of the cattle farmed in England and Wales. ²

11.4 Sheep production in the UK is based on a stratified breeding system. Of the20 million or so breeding ewes maintained in the UK during 1986-95, 6 million were kept in the hills and were specialised breeds well adapted to harsh conditions in these areas. Surplus female lambs from these hill ewes were sold to farmers in the upland areas, where they were mated with longwool breeds. Crossbred female offspring from these matings were sold to lowland farmers to be mated with lowland breeds to produce quality lamb carcasses demanded by the market. ³

11.5 The sheep industry is characterised by extensive buying, selling and movement, ⁴ not only as a consequence of the stratified breeding system, but also in response to price differentials across different regions. Furthermore, the expansion of sheep production during the 1980s and early 1990s itself led to the movement of larger numbers of sheep around the UK.

Sheep diet

11.6 The sheep diet is based on grass, supplemented by purchased feeds when necessary. At the time BSE emerged, most sheep farmers supplemented the diets of their stock with concentrates. However, the diet would vary according to whether the sheep were kept in the hills, the uplands or the lowlands, and according to the time of year lambing took place. Whereas hill flocks were rarely given concentrates, sheep kept in the uplands and lowlands were offered them, particularly the early lambing flock, which required winter housing and thus supplementary feed. Lambs born in winter would also require supplementary feed. ⁵

11.7 Concentrates were likely to contain some level of MBM, though the extentto which it was included cannot be ascertained with precision. However, inclusion rates were lower for sheep feed than cattle feed, and the per capita exposure to MBM would have been significantly lower for sheep than for cattle. ⁶ The feeding of MBM to sheep was prohibited by the ruminant feed ban that came into forcein June 1988. ⁷

Scrapie

11.8 Scrapie is a transmissible spongiform encephalopathy mainly affecting sheep, though goats are also susceptible. It was first recorded in Britain around 1732, and by the time BSE emerged it was widely recognised by farmers and vets. The symptoms are incoordination and intense itching - hence the name - leading tothe fleece being rubbed off against fences, posts and trees. Transmission occurs naturally between sheep, though precise routes are unknown. One route may be infected placentae. It is believed to spread between sheep in pastures and particularly in spaces where sheep are congregated, such as lambing pensand paddocks.

11.9 Vol. 2: Science provides details of the research undertaken since the 1960s to find out how scrapie is transmitted and what measures can be taken to control it. This body of knowledge became the basis for judgements in the Southwood Report on BSE (see vol. 4: The Southwood Working Party, 1988-89 for further details).

11.10 Farmers try to rid their flocks of scrapie by ensuring that scrapie-suspected animals are removed at the earliest opportunity. Selective breeding has also been used in an attempt to prevent scrapie from entering the flock by vertical transmission. For example, since scrapie was made a notifiable disease on 1 January 1993, the Meat and Livestock Commission has recommended that farmers implement a closed flock policy, with purchases only from scrapie-free flocksof preferably older ewes less likely to develop the disease. ⁸

11.11 When scrapie was made notifiable, there were no powers of compulsory slaughter. A compulsory slaughter and compensation scheme was not implemented until July 1998. However, agreement was normally reached with the farmer for submission of the head to a Veterinary Investigation Centre to allow a laboratory diagnosis. In general, only the first case reported in a flock and subsequently confirmed in a two-year period was sent for laboratory examination. Second and subsequent cases were confirmed on clinical grounds only. ⁹

11.12 It is accepted that before scrapie was made notifiable, official scrapie statistics (based on cases sent to Veterinary Investigation Centres for diagnosis) did not represent the true national incidence, since many farmers could identify scrapie themselves, and therefore would not call in the vet. In 1988, on the basis of a voluntary survey, it was estimated that a third of British flocks were affected, scattered throughout the UK. As discussed in more detail in vol. 2: Science, the incidence of clinical cases of scrapie in affected flocks of 100 or more sheep, estimated from the survey, was either 0.5 or 1.1 cases per 100 sheep per year. Extrapolation of these data to develop a picture of the national incidence of scrapie would not provide a robust assessment given some of the problems with the survey, not least the low sample size. But if such extrapolations were made they would indicate (albeit approximately) a much higher incidence of scrapie in the national breeding flock than suggested by the number of confirmed cases per year since scrapie was made notifiable (328 in 1993, 235 in 1994 and 254 in 1995). This suggests that either the incidence of scrapie has drastically fallen (since the survey results in 1988), or a robust assessment of its incidence is not yet available. ¹⁰