The importance of the PrP genotype in active surveillance for ovine scrapie.

Surveillance activities for ovine scrapie have expanded in the 21st century, following concerns about the potential for a hidden epidemic of bovine spongiform encephalopathy in European sheep populations. Large-scale surveys have been used to estimate the prevalence of scrapie infection. In this study we analyse data from the surveys in Great Britain between 2002 and 2004. When we estimate genotype-specific prevalences for each of the two screening tests used a difference is observed. One test underestimates the number of positive cases in genotypes classically considered to be at a low relative risk of developing clinical disease (ARR- and AHQ-containing genotypes). By comparison, the other test underestimates the number of positive cases in genotypes classically considered to be at an increased relative risk of developing clinical disease (VRQ-containing genotypes). These findings have implications for surveillance, disease control, and diagnostic test evaluation.

The use of databases to manage fertility.

Dairy farming now needs more records to be kept for quality assurance as well as for management. Herd fertility management is best brought about through the use of computerised records for each animal that integrate fertility, health and production. The development of dairy information systems over the last 25 years has allowed the creation of databases that give rise to "standards" of performance and "interference levels". These databases are of limited use for research unless the coding system has a structure and definition that works across herds. There is an increasing need to incorporate carefully coded disease records into these databases as there is increasing concern about welfare, zoonoses, assurance and the environment. Rules can be determined for satisfactory fertility so interference at an early stage is cost-effective. Integrated indices have been developed (using databases) that incorporate the costs of wastage caused by poor fertility, thus highlighting the priorities for management. Databases are best operated near to the farm, either in the veterinarian's office or on-line in the farm office. Databases can be made into expert systems that deliver high standards of fertility management. A checklist is included that can be followed to analyse the causes of poor fertility in a dairy herd.

Incidence of clinical mastitis in dairy herds in England.

The annual incidence of clinical mastitis was measured in 144 Holstein/Friesian dairy herds in England (average size 132 cows) during 1994, 1995 and 1996 by means of carefully defined mastitis indices. The mean annual incidence of the disease over the three-year period was 43.4 quarter-cases per 100 cows, and the disease affected 25.9 per cent of the cows in the herds, with 1.6 quarter-cases per affected cow. In terms of cow-cases, the mean incidence was 39.9 cases per 100 cows in the herd and hence the ratio of quarter-cases to cow-cases was on average 1:1. The proportion of repeat quarter-cases was on average 19.4 per cent, and the recurrence rate was 18.3 per cent. The new infection rate was 28.3 per cent.

The costs of production diseases in dairy herds in England.

Economic losses due to common health problems in dairy cattle were investigated in 90 Friesian/Holstein herds (average size 152 cows), which calved in England during the 1992/1993 season with an average annual yield of about 6000 l per cow. By using only the direct costs of common production diseases and other health problems (mastitis, lameness, vulval discharge, treatments for oestrus-not-observed, retained foetal membranes, milk fever, twinning, calf mortality and aid at calving), the cost of ill health in a 100 cow herd with average rates of these problems (compared with target levels) was estimated at Pounds 6300 per year. The costs ranged from Pounds 1200 (average of the top 10%) to Pounds 13600 (average of the worst 10% of the herds). The main losses were due to mastitis and lameness (38 and 27% of health cost, respectively).

Culling in 50 dairy herds in England.

A survey of 50 Friesian/Holstein dairy herds (average size 178 cows) in England investigated the rate of culling and the reasons for disposal and death over three years from 1990 to 1992. The average total annual culling rate was 23.8 per cent (22.0 per cent sold and 1.8 per cent died). Of the disposals, 54 per cent were culled by the end of their fourth lactation. Poor fertility was the most important reason for culling (36.5 per cent of disposals), followed by management policy (11.5 per cent), mastitis (10.1 per cent), bovine spongiform encephalopathy (BSE) (7.4 per cent) and lameness (5.6 per cent). The most common causes of death were mastitis (8.9 per cent) and BSE (11.5 per cent), but 46 per cent died for unknown reasons.

Incidence of production diseases and other health problems in a group of dairy herds in England.

The incidence of major production diseases and other health problems was investigated in 90 Friesian/Holstein dairy herds in England (average size 152 cows) for cows calving during 12 months in 1992-1993. The mean incidence of mastitis was 33.2 cases per 100 cows, and it affected 20.6 per cent of the herd with 1.6 cases for each affected cow. On average, 17.4 per cent of the cows suffered from lameness, with 1.4 cases per affected cow and a total of 24.0 cases per 100 cows. Cows treated for oestrus-not-observed totalled 33.6 per cent, with 46.4 treatments per 100 cows. The incidence of milk fever was 7.7 cases per 100 cows. Retained fetal membranes affected 3.6 per cent of cows. Vulval discharge affected 15 per cent of the average herd with 1.4 treatments per affected cow and a total of 21.2 treatments per 100 cows. The mean incidence of twinning was 4.1 per cent. Calf mortality claimed 7.8 calves per 100 calves born. The average number of cows given aid at calving was 8.7 per 100 cows calving.