AN APPROACH TO THE STUDY OF MASTITIS CONTROL IN ORGANIC DAIRY HERDS IN THE UK

M. HOVI AND S. RODERICK

INTRODUCTION

Most conventionally managed dairy herds in the UK operate a system of mastitis control that places emphasis on the use of prophylactic treatments at the end of each lactation (dry cow therapy, DCT). In organic systems the routine use of prophylactic antibiotics is prohibited. A survey of organic livestock producers in the UK has revealed that dairy producers adopted a range of treatments, dominated by combinations of the therapeutic use of antibiotics and homeopathic remedies and homeopathic nosodes (Roderick et al.,1996). A detailed study of the incidence, treatment strategies and financial implications of mastitis in organic dairy herds in the UK is presently being conducted. This paper will focus on the methodologies being adopted and will present preliminary findings.

METHODOLOGY

The study has been conducted on a sample of 16 organic and seven conventional herds. The sample of organic herds at the start of the study represented a significant proportion of the national organic herd. The data collection methods can be broadly categorized into the following components:

1. A longitudinal epidemiological survey of the sample herds.
2. A series of case studies conducted on the survey herds.
3. A comparative analysis using data collected from National Milk Records.

1. The objective of the longitudinal study was to gain epidemiological data, individual animal details and measurable environmental and management data so as to describe the incidence of the disease and to understand some of the risk factors associated with the disease and its control.
2. A case-study approach was initially instigated so as to gather detailed information on the control strategies adopted. Given that producers adopt a range of complex strategies, it was felt that the most effective method of achieving this was to combine recorded details with open-ended discussion with owners and herdsmen. These informal interviews were also used to assess perceptions of the disease and its control.
3. National Milk Records were used to gain access to detailed information on milk and herd production. These data will be combined with data collected from the longitudinal study to allow a detailed analysis of the disease and production relationship. More precise data gathered from the case-studies will also be integrated with these data to provide detailed financial and economic analyses.

RESULTS

To date, a limited preliminary analysis of the data has been conducted and the trends can be summarized as follows:

• mastitis incidence was similar on organic and conventional farms;
• there were large variations in mastitis incidence between the organic farms;
• overall, dry period mastitis was more common in organic than conventional herds;
• there were large variations in dry period mastitis on organic farms;
• both bulk tank and individual cow somatic cell counts (SCC) were higher on the organic farms;
• there were no obvious parity (number of calves) effects related to SCC;
• bulk tank SCCs were higher on the organic farms receiving no SCC payment premiums as compared to those receiving premiums for low bulk tank SCCs;
• homeopathy was the main alternative to antibiotics on organic farms;
• antibiotic use was significantly lower on organic farms (0.45 tubes/cow/year) than on conventional farms (5.9 tubes/cows/year);
• approximately 68 percent of conventional antibiotic use was in the form of dry cow therapy;
• milk withdrawal periods on organic farms were significantly longer after antibiotic use than on conventional farms;
• milk withdrawal periods for "alternative" therapies were shorter than that for antibiotic use on both conventional and organic farms.

DISCUSSION

This discussion will focus on the methodology adopted and its relevance to the study of animal health on organic farms. Whereas the epidemiological methods applied were similar to those adopted for the study of conventional systems, the informal interview methods proved to be particularly relevant to both the study of organic health control methods and the perception of disease amongst organic producers.

Since all of the conventional farms in the study adopted universal therapy and prophylaxis using antibiotics, the measure of veterinary inputs proved to be a straight forward recording process. Organic producers tend to use a wide range of techniques and applications. Detailing these was only possible through a process of interview, discussion and observation. For example, whereas some producers may see homeopathy as a straight forward substitute for antibiotics, others see this as a more holistic approach. This latter approach, requiring attention to detail and individual knowledge of each animal in the herd, does not lend itself to standard methods of measuring veterinary inputs.

Further to the detailed description of control methods, informal interviews were also important in determining farmer/herdsperson perception of disease. It has become clear that the attitude to the relationship between somatic cell count and milk quality is different between the organic and conventional sector. Whereas low levels of SCC is accepted conventionally, maximum levels amongst organic producers has a greater significance. This perception was also noted at farmers' meetings designed to disseminate the preliminary findings of the study.

It was concluded that whilst the informal interview techniques, together with mid-term feedback of research results to the participating farmers, may result in "research bias" in future data collection, the enhanced understanding of the system gained from this methodology is extremely valuable. In a situation where mainstream advice differs significantly from the organic approach, the producers themselves have to act as innovators of new technologies. It was suggested that a participatory approach in defining final research goals and in identifying farmer acceptability of potential research recommendations, would be particularly useful in this context. Participatory Rural Appraisal (PRA) methodologies that have been widely used in other farming systems research in the developing world, might prove to be of equal benefit to organic farming research generally and to animal health and welfare issues specifically.

REFERENCE

Roderick, S., Hovi, M. and Short, N. (1996): "Animal Health and Welfare in Organic Farming: Research Priorities", AHT Report, University of Reading.