Experimental reproduction of cyanogenic poisoning by star grass (Cynodon nlemfuensis Vanderyst var. nlemfuensis cv. “Florico”) in cattle

Abstract

We experimentally reproduced star grass (Cynodon nlemfuensis Vanderyst var. nlemfuensis cv. “Florico”) poisoning in cattle. Star grass was planted in four shaded (1, 2, 3, and 4) and three sunny paddocks (5, 6, and 7) and were fertilized with the equivalent of 0, 750, 200, or 100 kg/ha urea. Fresh plant leaves were collected from each paddock and fed to 8 calves aged 5 months to 1 year at 10g/kg live weight. Clinical examinations were performed pre- and post-feeding. Fresh leaves were also subjected to sodium picrate paper and diphenylamine tests to evaluate hydrocyanic acid and nitrate concentration, respectively. Clinical signs of poisoning by the star grass cv. “Florico” in cattle were observed 5-15 minutes after ingestion; these included wobbling, muscle tremors, frequent and/or dripping urination, tachycardia, ruminal atony, depression, red ocular mucous membranes, and bright red venous blood. Three animals became severely ill, 4 manifested mild to moderate clinical signs, and 1 did not become ill. The 3 severely ill bovines received a thiosulfate and sodium nitrite solution at a dose of 40ml/100 kg live weight, intravenously (IV). Florico star grass poisoned bovines and the reaction to the sodium picrate paper and diphenylamine tests was more significant for samples cultivated in the shade and with high nitrogen fertilization. Florico grass utilization should be avoided in a silvopastoral system.