Cobalt deficiency in ruminants from Tocantins State, Brazil: an underdiagnosed nutritional challenge?

Although mineral deficiencies are well-documented in Brazil, they continue to cause significant economic losses, particularly in animals raised under extensive grazing systems. Cobalt (Co) acts as a cofactor for the enzyme methylmalonyl-CoA isomerase, the sole metabolic pathway for propionate conversion and subsequent glucose synthesis. It is also essential for vitamin B12 synthesis, which supports hemoglobin formation, carbohydrate and lipid metabolism, and nucleic acid synthesis. Deficient animals exhibit anorexia, weight loss (despite forage availability), anemia, ruminal atony, and lignophagia. To describe the first reported cases of cobalt deficiency in sheep and cattle in Tocantins State, Brazil, focusing on clinical history, nutritional and hematological aspects, and impacts on animal health. The study was conducted across three distinct farms in Tocantins, Northern Brazil. Diagnosis involved clinical history, physical examination, hematological analysis, blood glucose and ketone measurements, urinalysis, rumen fluid evaluation, fecal parasitology, necropsy, and liver cobalt quantification via spectrophotometry. Therapeutic diagnosis was confirmed through vitamin B12 administration and cobalt supplementation. All three farms exhibited cobalt deficiency cases, with primary symptoms including lignophagia, anorexia, progressive emaciation, and mortality. Hematological findings revealed normocytic normochromic to macrocytic hypochromic anemia, occasional leukocytosis, hypoglycemia, and normal β-hydroxybutyrate (BHB) levels. Urinalysis showed no abnormalities. Rumen fluid analysis indicated complete microbial inactivity with indigestion. All treated animals achieved full clinical recovery without relapse. Cobalt deficiency in sheep and cattle in Tocantins poses a significant health and productivity threat. The positive response to vitamin B12 and cobalt therapy underscores the importance of proper nutritional management. This first report of cobalt deficiency in previously unmapped regions alerts farmers and veterinarians to prioritize mineral monitoring and supplementation to mitigate economic losses and ensure animal welfare.