Case Report - Chronic oak toxicity (Quercus suber) in beef cattle in the south of Portugal

Oak toxicity in cattle results from ingestion of acorns, buds, leaves, sprouts, and saplings from several species of trees in the genus Quercus, all of which contain high concentrations of tannins. Consumption of acorns by ruminants, principally between late summer and early winter, is common in the south of Portugal, where there is a high prevalence of Quercus suber. Oak poisoning can lead to progressive damage to the kidneys and may result in renal failure and death. This study involved 17 beef cows that died of chronic oak poisoning related to ingestion of Quercus suber. The most relevant findings from necropsy examinations were abdominal fluid accumulation, atrophic/fibrotic kidneys, mesenteric and sub-mandibular edema, absence of body fat reserves and muscle atrophy, and weight loss. The most significant histopathologic finding was chronic interstitial nephritis. Elevated blood urea nitrogen, creatinine, and K+ values and reduced albumin values were found in 4 cows examined ante-mortem. Straight-bred Mertolengo cows appeared to be highly resistant to oak toxicity.