Urea poisoning in cattle: A brief review and diagnostic approach

Urea is an organic compound characterized as a white, solid, and hygroscopic substance. It is recognized as a source of non-protein nitrogen (NPN) and is widely used as a partial replacement for protein in cattle diets due to the ability of the ruminal microbiota to convert it into microbial protein. Despite the advantages of using urea, it also has limitations, particularly the proximity between metabolizable and toxic or fatal doses. Furthermore, for safe use, a period of adaptation is necessary for the animals. Poisoning is characterized by rapid and generally fatal development, which is frequent in non-adapted animals but can also occur in those with previous adaptations. The aim of this study was to characterize the clinical, epidemiological, and pathological aspects of urea poisoning through a brief review and a retrospective study. In addition, interviews were conducted with veterinarians who frequently send diagnostic material to the Laboratory of Anatomic Pathology of the “Faculdade de Medicina Veterinária e Zootecnia” (LAP-FAMEZ) to assess their perception of the outbreaks of urea poisoning. The objective was to obtain a comparative scenario between published cases and those received by the laboratory while considering the real situation of this condition in the field. During this retrospective study, only four outbreaks were investigated; in one, the diagnosis was possible through experimental reproduction. Of 35 interviewees, 88.9% said they had seen more than one case compatible with urea poisoning, but 87.5% did not perform a necropsy and/or send material to confirm the diagnosis. The results show that the reality of urea poisoning may be very distant from that reported in previous studies due to the difficulty often observed in the diagnostic approach, so we developed a flowchart aiming to provide a useful guide for field veterinarians. RESUMO: A ureia é um composto orgânico, que se apresenta como uma substância branca, sólida e higroscópica, e é reconhecida como fonte de nitrogênio não proteico (NNP), sendo amplamente utilizada como fertilizante e também como substituto parcial de proteína em bovinos devido à capacidade da microbiota ruminal de convertê-la em proteína microbiana. Apesar das vantagens que envolvem o uso da ureia, ela também apresenta limitações, a principal delas é a proximidade entre doses metabolizáveis e tóxicas ou fatais, e para que seja utilizada com segurança é necessário um período de adaptação dos animais. A intoxica