Sustainable dairy farming and fipronil risk in circular feeds: insights from an Italian case study

Circular feeds, such as grain dry distillers, citrus pulp, cane molasses, and potatoes peels, are co-products of biomass processes. They are currently proposed in animal nutrition to improve the environmental and economic sustainability of the food production chain. In this paper, we report a case study involving fipronil, a pesticide currently not authorized for agriculture within the EU, but used in the Americas, Eastern Europe, and Asia. Fipronil was found at a mean level of 0.49 mg/kg, in a grain dry distiller batch administered to dairy cows. This finding, along with other evidence of potential fipronil presence in feed materials, prompted us to evaluate the risk to food safety and food security from 12 different conventional and sustainable feeding regimens. To this purpose, we considered a fipronil feed-to-milk carry-over rate of 0.52, the tolerance levels in fodders and food from The EU, Codex Alimentarius, and US-EPA, and the Acceptable Daily Intake (ADI) of 0.0002 mg/kg body weight for adverse effects on thyroid function in dairy cows. Under a conservative scenario, fipronil-contaminated potato peels and grain distillers in the feeding regimens may play a pivotal role in exceeding the EU Maximum Residue Level (MRL) in bovine milk and fat (0.005 and 0.030 mg/kg, respectively). Hay-based diets with soybean hulls and cane molasses show negligible risks (Hazard Index ∼ 1). In all cases, the ADI exceedance suggests the need to evaluate thyroid function in dairy cows exposed to fipronil as a food security factor.