Nitrate/nitrite poisoning in dairy cattle from Santa Fe, Argentina.

BOLCATO, M.; MACHADO, S.; ALLASSIA, M.; RUIZ, M.; ANGELI, E.; AGUIRRE, F.O.

Bolonia

Congreso; 50th National Congress of the Italian Association for Buiatrics; 2018

50th National Congress of the Italian Association for Buiatrics

Nitrate intoxication is in veterinary medicine most commonly related to the use of nitrate-accumulating plants for livestock forage. Of secondary importance as sources are nitrate or nitrite fertilizers and surface waters contamined by fertilizers or nitrogenous animal waste products (Davis, 1980; Knight, 1985).Ruminants are particularly at risk of acute, fatal nitrate-nitrite poisoning. They are 10 times more sensitive to nitrate than monogastric animals because microorganisms in the rumen reduces nitrates to nitrites then ammonia for microbial growth (Nicholson, 2007). Nitrite is toxic to erythrocytes because it converts hemoglobin into methemoglobin, an oxidized form of hemoglobin, which cannot bind to oxygen.In a rural property in the city of Ramona, in Santa Fe, Argentina, eight of 35 dairy cattle showing clinical signs of poisoning. Clinical examinations of affected animals and necropsy of the dead were performed. The suspected poisoning cows were immediately treated with 1% solution of methylene blue (10mg/Kg). The pasture was observed for the possibility of exposure to toxic plants or water.Affected animals presented weakness, ataxia, muscular tremors, cyanotic mucous membranes, respiratory disorders and progression to sternal decubitus. Death occurred after one day post treatment and, without treatment, in a few hours. At the gross pathology animals showed darkened blood (chocolate-colored) of difficult coagulation, petechiae and suffusions in heart, pulmonary emphysema and cyanosis of the mucous membranes and nipples.In the pasture the presence of Cynodon spp., Chenopodium album, Conium maculatum were detected.Diagnosis of nitrate intoxication was based on observed clinical signs, chocolate-brown blood and exposure to the toxic plant. The intoxication occurred in a rainy period (November to January), that followed a drought season (Mayto October). The occurrence of a drought period followed by a rainy period is considered an important factor that results in the increase of nitrate concentration in the plants, causing an accelerated growth and absortion of toxic levels of nitrates (Riet-Alvariza, 1993; Cheeke, 1998; Radostits et al., 2007).