Nitrate and nitrite poisoning in sheep and goats caused by ingestion of Portulaca oleracea

Abstract

Three outbreaks of poisoning by Portulaca oleracea were reported in sheep and goats in Northeast Brazil. In the first outbreak, 8 out of 20 sheep were affected and later died. In the second outbreak, three goats and one sheep died out of a flock of 30 animals that included both species. In the third outbreak, two out of 19 sheep were affected, and they recovered after a treatment of 2% methylene blue at a dose of 4 mg/kg body weight. In the first and second outbreaks, the animals ingested P. oleracea after it was cut and offered in feeders. In the third outbreak, the flock was grazing in an area that had been invaded by the plant. To determine the toxicity, P. oleracea was administered experimentally at a dose of 80g/kg of body weight to seven sheep, weighing 19-30 kg. One control sheep received green grass. One to four hours after P. oleracea ingestion, the animals showed clinical signs of poisoning characterized by cyanotic mucous membranes, bloat, ruminal pH of 8-9, pollakiuria, aerophagia, involuntary movements of the upper lip, apathy, tachypnea and tachycardia. Five animals recovered, including one that was treated with 1% methylene blue, and two animals died. During necropsy, the mucous membranes were brownish, and the blood was dark brown. Diphenylamine tests of the plant and of rumen contents were positive for nitrates. Positive results for nitrates were also found in 24 samples of P. oleracea that were collected in different places in the states of Pernambuco and Paraíba. We conclude that P. oleracea accumulates nitrates at toxic levels and may cause poisoning in sheep and goats.

Clinical and toxicological findings in nitrate and nitrite poisoning in cattle in Northeastern Brazil

“…In previous studies in Northeastern Brazil nitrate and nitrite poisoning was associated Pennisetum purpureum and Echinochloa polystachya in cattle (Medeiros et al 2003) and by Portulaca elatior in goats and sheep (Simões et al 2018). In the outbreaks reported herein the disease was caused by P. purpureum and Brachiaria spp, mainly Brachiaria brizantha.…”

Performance, Methane Emission, Nutrient Utilization, and the Nitrate Toxicity of Ruminants with Dietary Nitrate Addition: A Meta-analysis from In Vivo Trials

“…On the other hand, it was found that sheep tolerate the double amount of nitrate administration in the cattle. A study on nitrite poisoning in goats and sheep showed that sheep tolerate up 50% of the nitrate conversion, while death occurs when the nitrate conversion rate exceeds 80% (Simões et al, 2018). Sheep were reported to have more resistance to nitrate toxicity among the ruminants, and their tolerance to the dietary nitrate can be enhanced by acclimation (Alaboudit & Receivedg, 1985).…”

Plants causing poisoning outbreaks of livestock in South America: A review

“…Portulaca oleracea (Portulacaceae) is a plant that usually accumulates nitrates and causes outbreaks of intoxication in the Northeast region of Brazil in pastures invaded by it or when it is cut and administered in feed troughs ( Simões et al, 2018 ). In Chile, poisoning by nitrates and nitrites has been described in cattle by the ingestion of Silybum marianum (Asteraceae) ( Freire and Araya, 1988 ).…”