The Veterinary Record, March 7,1998 Exploratory study on the economic value of a closed farming system on Dutch dairy farms G. van Schaik, A. A. Dijkhuizen, G. Benedictus, H. W. Barkema, J. L. Koole Veterinary Record (1998) 142, 240-242 A closed farming system may prevent the introduction of infec- tious diseases on to dairy farms and could be a good starting point for the eradication of these diseases. In order to intro- duce a closed farming system, farmers need to be made aware of how these diseases are introduced into the herd. Farmers will be more likely to implement a closed farming system when the economic value is quantified and attractive. An exploratory study was carried out to investigate the technical and economic results of closed dairy farms. Farms that purchased cattle and/or shared pasture (dermed as 'open' farms) differed in technical results from farms that did not ('closed' farms). The results of the discriminant analysis showed that the 'closed' farms incurred lower costs for veterinary services, had a lower average age at first calving and a higher birth rate per 100 dairy cows. A linear regression analysis was carried out to investigate the influence of the farming system on economic performance. Being 'closed' was found to increase the net profit by £0.31 per 100 kg of milk, or approximately £25 per cow per year or 5 per cent of the typical net return to labour and management (£1 = Dfl 2.80 in November 1996). A MAJOR aim of the European Union (EU) livestock policy is to improve the health of farm animals in the member states. Preventive herd health control at farm level is considered to be the major tool to bring about this improvement. National borders are replaced by borders around individual farms implying that indi- vidual farmers are responsible for their animals' health. Farmers need to be aware of the risks and management opportunities in order to maintain or improve the health of the animals on their farms (Julicher and others 1993). Dutch agriculture is characterised by an intensive animal produc- tion system. In the past few decades the concentration of animals as well as the number of national and international contacts, for exam- ple the import or export of live cattle, have increased considerably (Nagel 1995). Dutch animal production depends strongly on inter- national markets and, together with the favourable geographical sit- uation of the country, this results in the large scale import and export of animals and animal products, putting strong pressure on maintaining a good health status (Tazelaar and Gerats 1995). Statistics for 1994/95 show that there were approximately 1-7 million dairy cows on 32,000 specialised dairy farms in the Netherlands (Agricultural Economics Research Institute 1996). The farms had on average, 53 cows and 31 hectares of land with an average milk production of 6954 kg per cow per year. Surplus cattle were sold as calves, heifers or fattening cattle. About 50,000 head of cattle were sold for live export annually. ,According to the Dutch extension services the major routes through which an infectious agent can be introduced on to a farm are (Koole 1995): - Contact with other dairy cows, for example with purchased cows or cows at cattle shows; - Contact with other animal species that are potential carriers of the disease, for example sheep, goats, rats and dogs; G. van Schaik, MscAgric, A. A. Dikhuizen, MscAgric, PhD, Department of Economics and Management, Wageningen Agricultural University (WAU), Hollandseweg 1, 6706 KN Wageningen, The Netherlands G. Benedictus, DVM, PhD, H. W. Barkema, DVM, Animal Health Service, PO Box 361, 9200 AJ Drachten, The Netherlands J. K. Koole, MscAgric, National Reference Centre for Livestock Production, PO Box 482 6710 BL Ede, The Netherlands fLi .. - Transmission by humans, for example visitors and veterinarians; - Transmission by machinery, for example cattle trucks, manure spreaders and other tools; - Transmission by foodstuffs or water, for example ditch water; - Transmission by air. Research was carried out to investigate the number and kind of contacts which, on average, Dutch dairy, pig and mixed farms have (Nielen and others 1996). When risky contacts, such as buying cat- tde and the visits of a veterinarian, were combined with less risky contacts such as the transport of feed and milk, and social human contacts, cattle farms had a median of 6-9 contacts per day. A sur- vey of the Animal Health Service in the northern provinces of the Netherlands in 1995 showed that 55 per cent of the dairy farms had purchased cows in the preceding year (G. Benedictus, personal communication). Direct and lengthy animal contacts are the most important risk factors, followed by contacts with people or animal transport vehicles, animal products and transmission by feed, ver- min or air (Wentink and others 1993, Koole 1995, Horst and others 1996). The most usual way in which bovine herpesvirus 1 (BHV-1) iS transmitted between farms is by the introduction of latently infected animals on to a farm (Msolla and others 1981, Pastoret and others 1984). To introduce a closed farming system farmers need to be made aware of the risk of the introduction of infectious diseases on to the farm. Farmers will be more likely to implement a closed farming system when they are aware of the economic value of such a system. However, the economic value of maintaining stable ani- mal health and a closed farming system has not been quantified. The present study explores the economic value of the adapta- tions in management required to introduce a closed system on to dairy farms to prevent the introduction of diseases and to improve the health of animals on the farm. According to the advice of the extension services, the Animal Health Service and National Reference Centre for Livestock Production, a closed farming sys- tem may prevent the introduction of, for example, BHV-1, bovine virus diarrhoea virus, leptospirosis, paratuberculosis and salmonel- la on to a farm, and can be a good starting point for the eradication of these infectious diseases. Further study will be necessary to reveal the epidemiological characteristics of a closed farming sys- tem. This study evaluates the advice of thet,extension services on the economic characteristics of a closed farniing system. Materials and methods An exploratory study was carried out to investigate the techni- cal and economic results on open and closed dairy farms. The data were derived from an accounting system for Dutch dairy farms (DELAR) and cover a period of two years. DELAR iS used on approximately 2500 farms and provides each farmer with infor- mation on average animal performance (milk production and cattle credits), land use (forage production and some other crops), fodder consumption (concentrates, forage and milk products) and remaining costs for fertilisers and contract work. The dataset con- tained data from 1485 farms for 1991/92 and 1992/93. The farms were grouped by several variables present in the accounting system, namely the income from, or the costs of, sharing pasture, the numbers of animals purchased, and the numbers of ani- mals reared for or on other farms. If a farrm did not share pasture, rear animals for or on other farms, or purchase cattle, it was defined as a 'closed' farm; otherwise the farm was defined as 'open'. To gain an insight into which variables accounted for the differ- ences between the open and closed farms, multivariate analyses (discriminant analysis and regression analysis) were carried out. Discriminant analysis is a statistical technique for studying the 240 group.bmj.com on December 2, 2014 - Published by http://veterinaryrecord.bmj.com/ Downloaded from