The use of grey zone products at the dairy farm

Farmers use a wide range of products for their livestock for prevention or treatment of health issues in dairy cows and to clean or disinfect the milking system. Besides registered veterinary medicinal products and biocides, there are many other products available for this purpose; the so-called grey zone products. The use of these grey zone products may pose a potential health risk to livestock and consumers of animal derived products. The aim of this study was to gain more insight in the use of grey zone products at dairy farms, the potential presence of illegal substances and the potential human health risks related to the use of these grey zone products. For this purpose, the following steps were followed: 1. Exploring the use of grey zone products by interviewing dairy farmers and experts; 2. Online search on availability of grey zone products; 3. Chemical analysis of a selection of these grey zone products and 4. Development of a risk classification method for grey zone products. Interviews with experts and a limited number of dairy farmers were performed. This showed that grey zone products are most frequently used in relation to udder and claw care. Main incentives for use were the need to reduce or omit antibiotics use and to find effective alternatives for persistent problems like mastitis and Mortellaro (digital dermatitis). Products can be obtained from veterinarians, animal supply shops (e.g. Welkoop) and wholesalers. Also, a large product range is offered on online web shops. As grey zone products are expected to be easily obtained online, an online screening of cattle care products was performed. In total, 18 web shops were found to offer a substantial product range of cattle care products. These web shops were screened using expert judgment for products with a potential risk to human health when residues are found in dairy products. This resulted in 42 grey zone products of which 11 products were selected for chemical analysis of their composition. Reasons for selection were unclear ingredient declarations (n=3) and discrepancies between claims and declared composition (n=9). An example of the latter is a product claiming antibacterial or anti-inflammatory effects, which cannot be substantiated by the listed ingredients. Such products could indicate the presence of illegitimate substances. The products could be categorised into skin care products (n=3), dry-off products (n=2), respiratory care products (n=2), immune system supporters (n=3) and gastrointestinal product (n=1). An analytical protocol was developed to determine whether the selected products contained illegal and/or undeclared substances. The analytical strategy was based on an untargeted LC-HRMS method combined with the data processing tool Compound Discoverer. Additional analyses were performed, but due to time and budget constraints, only focused on painkillers, hormones and coccidiostats. Analysis of these selected 11 products with this strategy did not yield illegitimate or undeclared substances with potential risks. Apart from the chemical analysis, a risk classification method was developed that allows for a food safety risk prioritization of grey zone products. Google Scholar and Scopus were used to perform a literature study on general risk ranking methods of products. No pre-existing risk ranking strategy was found that can prioritize products on food safety risk. The literature study revealed only methods that can prioritize active substances within products. Therefore, a risk classification strategy was developed using scores for severity with respect to human health, probability of exposure and the exposure intensity. Because of the wide variety of grey zone products that are available, a decision tree to rank the severity when using grey zone products was established. Based on expert judgement, a selection of products (n=10) obtained from the online screening was used to test and adjust the risk classification method. Many products state a health or disinfection claim without registration or authorization as a veterinary medicine or biocidal product. Based on the final classification of products, follow up actions can be taken. Overall, the product testing showed that the developed risk ranking method allowed for a classification of grey zone products based on a potential food safety risk. The results of this study show that many grey zone products are available for use at the dairy farm. The developed risk classification method can be used to select those products which need further attention. Although no illegitimate substances or chemical hazards were identified in the selected products, potential legal issues related to discrepancies between claims and composition were found. Also, it revealed significant prevalence of incomplete or unclear ingredient declarations.