Hazardous substances present in crop-livestock recycling system: hazards to animals and humans

The symbiotic relationship between agriculture and animal husbandry has long been a cornerstone of sustainable farming practices. By integrating crop residues and animal wastes back into the farming system, this model promotes resource efficiency and reduces environmental footprints, delineating a path toward ecological farming. However, this system, while sustainable, is not without its challenges. Chief among these are the hazardous substances that can accumulate within the cycle, posing significant risks to animal health and, by extension, to human consumers. These substances can originate from multiple sources - including pesticide residues on crop remnants, heavy metals present in soils absorbed by plants, veterinary pharmaceuticals used in livestock, etc. Their presence within the recycling system necessitates a comprehensive understanding of their distribution patterns, the mechanisms through which they affect animal health, and the potential residual effects on human health through the consumption of animal products. This review aims to delve deeply into these issues. By reviewing recent five years researches and case studies, it seeks to characterize the occurrence, environmental fate, and toxicological effects of hazardous substances within the crop-livestock recycling system, with particular attention to their impacts on both target and non-target organisms. Furthermore, it investigates the physiological and biochemical pathways through which these substances exert detrimental effects on livestock, thereby shedding light on the complexities of their impacts. Understanding these facets is crucial for developing strategic interventions to mitigate these risks. Hence, our discussion will also explore potential solutions and management practices aimed at minimizing the presence and impact of hazardous substances within this integrated system, thereby ensuring its continued viability as a sustainable farming practice.