Disease patterns of the diseases appear to be multivariate responses to

A . Sundrum Livestock Production Science 67 2001 207 –215 209 ¨ and Kopke 1994. The study showed that organic reduced production level in organic livestock farm- agriculture has clear benefits in reducing environ- ing Vaarst et al., 1993; Boehncke, 1997. On mental pollution in comparison to conventional average, milk yield per cow per year in organic agriculture. production is lower compared to conventional pro- To assess nutrient losses on the farm level, the duction BMELF, 1997; Kristensen and Kristensen, most common methodologies involve using balance 1998. Because of the renunciation of supple- sheets of the whole farm. Calculations demonstrate mentation by conventional produced foodstuffs, ge- that the systemic effect of organic agriculture has netic performance capacities are often not exhausted. great implication on the nutrient balance and the Although the relationship between milk yield and balance-surplus in relation to the product Halberg et predisposition for diseases is not well understood, al., 1995; Spiekers and Hahner, 1995; Hoppe et al., there are reasons for the assumption that high 1996; Geier et al., 1997; Martinson, 1998. There is yielders react to inadequate conditions more sensi- reason for the assumption that the benefit of the tively than animals with an average performance system-related factors on minimising pollution are Butler and Smith, 1989; Wanner, 1995. much more effective as compared to management- Mastitis related factors, such as increasing animal perform- Concerning the incidence of mastitis, studies ance per animal per year. For example, reducing revealed that mastitis was of the same or even of 21 nitrogen input of 100 kg N ha is more than doubly greater relevance on organic than on conventional efficient in relation to the balance surplus than farms Augustburger et al., 1988; Offerhaus et al., 21 increasing average milk yield for 1.000 kg cow 1993; Krutzinna et al., 1996; Weller and Cooper, and year Mejs and Mandersloot, 1993. 1996; Spranger, 1998. In contrast Vaarst and By analyzing agricultural energy utilization Enevoldsen 1994 and Ebbesvik and Loes 1994 through system modelling, Refsgaard et al. 1998 found a lower incidence of clinical mastitis in found conventional dairy production to be more organic compared to conventional dairy herds. It is intensive with a greater feeding ration and a higher most likely that some local or national conditions proportion of high-protein feed, but also higher like traditions for management, use of medication or yields. However, the conventional yields were not herd size could explain differences between the sufficiently higher to compensate for the extra use of results. However, the limitation of the data do not energy compared with the organic feeding ration. justify further statements. In summary, the basic standards of organic farm- Results about the incidence of reproductive dis- ing provide suitable tools to minimise environmental orders and other diseases in organic dairy herds are pollution and nutrient losses on the farm level. These less significant due to a small number of farms seem to be more effective than measures in conven- within those studies. However, studies in different tional production. However, there is a high vari- countries showed that the reproductive life span of ability within organic farms in relation to their dairy cows was significantly higher in organic com- efforts and their nutrient efficiency. pared to conventional farms Offerhaus et al., 1993; Ebbesvik and Loes, 1994; Krutzinna et al., 1996. ¨ According to Enevoldsen and Grohn 1996, most

4. Disease patterns of the diseases appear to be multivariate responses to

a complex set of interrelated causal factors and are Metabolic disorders often due to mistakes of the farmer, inadequate Looking at the disease patterns as an indicator of handling and inappropriate housing conditions. Man- animal health at herd level, several authors found a agement-related factors, such as regular checks of decrease in the incidence of metabolic disorders on the milking machine, feed analysis and the calcula- organic compared to conventional farms Ebbesvik tion of the diet are, and prove to be, of high and Loes, 1994; Vaarst and Enevoldsen, 1994; Krut- importance for animal health Schukken et al., 1990; zinna et al., 1996. The decrease in metabolic Bartlett et al., 1992; Barkema, 1998. Whether these disorders is discussed as a factor of a general management-related factors are practised differently 210 A . Sundrum Livestock Production Science 67 2001 207 –215 between the two production methods cannot be In summary, comparative studies investigating the concluded from the present data. However, it can be health situation of organic and conventional dairy supposed that the management-related strategies farms show that there seems to be no fundamental mentioned above are more often used and farmers difference between the production methods with are more aware of the benefits of management- reference to the animal health status of dairy cows. related factors on highly specialised farms than on Management is the most important factor in both mixed farms. Due to their reliance on efficient production methods. However, organic livestock nutrient circulation, mixed farms follow, in most farming creates stronger demands on the qualifica- cases, the basic concept of organic farming, although tion of the farm management. The risk for inappro- the degree of mixture can be widely different priate handling increases when capacities are over- Hermansen and Kristensen, 1998. Feeding, hand- taxed due to requirements of multiple demands. ling and taking care of the farm animals are in competition with various other farm activities, being different on organic mixed farms compared to highly

5. Animal welfare