Weeds Containing Nitrates cause Abortion in Cattle

Metabolism of nitrate by cattle

“…It is generally recognized that the toxicity of nitrate for ruminants depends upon its reduction to nitrite in the rumen and the combination of the nitrite with haemoglobin to form methaemoglobin in the blood. In addition to the acute symptoms that accompany nitrite poisoning, other conditions, such as a non-contagious abortion in cattle (Sund et al 1957), have been attributed to ingestion of materials high in nitrates. The current studies re-emphasize the very rapid conversion of nitrate into nitrite and ammonium ions in the rumen.…”

“…Lewis (1951) demonstrated that micro-organisms in the rumen of sheep reduce nitrate to ammonium ions with nitrite as an intermediate; enough nitrite was transferred to the blood to convert a considerable fraction of the haemoglobin into methaemoglobin. Sund, Wright & Simon (1957) reported that a non-contagious abortion observed among cattle pastured on marsh land in central Wisconsin apparently was a manifestation of nitrate toxicity.…”

Nitrate Accumulation in Some Iowa Crop Plants1

“…Bradley et al (1), on the basis of their experiments, have arbitrarily set the equivalent of 1.5% KN0 3 in forages as the lower toxic limit that may result in fatal poisoning. However, less than lethal amounts may result in abortions or serious reductions in meat or milk production (3,6,8).…”

Residue Reviews / Rückstands-Berichte

“…The clinical aspects of nitrate poisoning in stock, conditions under which nitrates are likely to accumulate in the leaves of certain plants, and lists of these plants have been reported by BRADLEY et al (1940), DAVIDSON et al (1941), GILBERT et al (1946), CASE (1957), andSUND et al (1960). The toxic effects of nitrate are caused by a reduction of nitrate to nitrite and the conversion by nitrite of haemoglobin in the blood to methoglobin: the animal dies from asphyxia.…”

“…Nitrate in plants is generally present in the form of potassium nitrate and increases in nitrate content have been associated with drought conditions and high soil nitrogen (GILBERT et al 1946, CASE 1957. SUND et al (1960) noted a high nitrate content in Urtica spp. and Rubus spp.…”