Outbreak of ruminal acidosis in cattle caused by the ingestion of hedge lucerne (Desmanthus virgatus L. Willd.) in Northeastern Brazil

Abstract

This study describes the epidemiological, clinical, and pathological aspects of an outbreak of ruminal acidosis and ruminitis caused by the ingestion of hedge lucerne (Desmanthus virgatus L.) in 70 cattle in the state of Paraiba, Northeastern Brazil. The herd had been transported from the state of Piauí to Paraiba. The deaths of the cattle occurred 15 days after the animals were introduced to a native pasture containing D. virgatus. All animals exhibited ruminal atony, which ranged from mild to severe. A total of 35 cattle died, with five undergoing necropsy. Initial clinical signs included apathy, followed by a marked increase in left abdominal volume, consistent with ruminal distension, absence of rumination (ruminal atony), lateral recumbency, and ultimately death. All affected animals were treated with oral administration of rumen fluid, enteral fluid therapy, and oral antacids. During this period, twenty animals succumbed to the condition, and an additional 15 died after being relocated, resulting in a 50% fatality rate. Significant gross pathological findings were observed primarily in the digestive system. The forestomachs were markedly distended, containing large amounts of reddish, pasty, and serous ingesta. A demarcation line was evident in the esophagus, separating the pale and bloodless distal esophagus from the congested proximal esophagus at the thoracic inlet, corresponding to the “bloat line." Frothy material was present in the tracheal lumen, indicating pulmonary edema. Additionally, rectal prolapse was noted. Histopathological examination revealed marked edema and severe hydropic (ballooning) degeneration of the basal layer in the forestomachs, along with intercellular edema. Separation of the epithelium from the lamina propria, forming multiple clefts, was observed, accompanied by areas of lymphoplasmacytic inflammatory infiltrate in the submucosa. This study demonstrates that this plant can cause severe gastrointestinal disturbances in cattle unaccustomed to its consumption and ingesting large quantities of the plant's shoots.