Impact of animal by-products inclusion on the multi-elemental composition and toxic element profiles in dry cat feedingstuffs

This study presents the first comprehensive multi-elemental assessment of 101 commercially available dry cat feedingstuffs across Europe, integrating pet food safety within a broader One Health perspective. Using inductively coupled plasma mass spectrometry and direct mercury analysis, 55 inorganic elements were quantified to examine how the presence of animal by-products as primary protein ingredients influences their distribution. Higher concentrations of Al, Ti, V, Sb, Bi, Hf, and especially As, were observed in animal-based compared with cereal-based feedingstuffs. The highest levels of toxic elements were found in fish-based formulations, with mean concentrations of As, Cd, Hg, and Pb reaching 475, 105, 7.8, and 193 µg kg⁻¹ , respectively. Selenium exceeded recommended limits in up to 75 % of pork-, 72 % of fish-, and 50 % of beef-based cat foods. Multivariate analysis using t-distributed stochastic neighbor embedding and Gain Ratio feature selection revealed distinct elemental patterns associated with primary protein component. Arsenic, Hg, and Sr were identified as the most discriminative elements, differentiating fish-based from poultry- and red meat-based products. The findings achieved indicate that fish-derived products substantially contribute to toxic element contamination, highlighting the need for improved ingredient sourcing. Addressing this issue is essential to safeguarding animal, human, and environmental health as interconnected components. • Animal-based cat food had higher concentrations of Al, Ti, V, Sb, Bi, Hf, and As. • Fish by-products are major contributors to toxic element buildup in cat food. • Recommended limits of Se were exceeded in fish-, ovine-, and beef-based products.