Sir, - I would like to record a clase of nitrate/ nitrite poisoning in cattle that had been gI:'azing a paddock in which Amaranthus hybridus group (red.wot) stalk was the only vegetation available. This weed is extremely common in crops ,in this area and may often constitute a large proportion of the feed ingested. In the DSIR Bulletin Poisonous Plants in New !Zealand (1948). Connor states that this weed has not been recorded as poisonous in New Zealand or Australia but points out that it has been found to accumulate nitrates in the stems and branches. In this case a paddock had been sown in crop but this had failed completely and t)Je whole area had overgrown with red root. Ewes were put on to graze this for 4 days and showed no ill effects. 18month-old cattle were then put on to graze off the long stalk prior to discing. There was virtually no leaf present. The cattle were put in the paddock at 10.30 a.m. At 5.30 p.m. the farmer noticed one animal was dead and moved the rest from the paddock. One beast was unsteady and was le£t behind; the others remained normal. On reaching the farm I examined the paddock for any other weeds or shrubs. None was present Post-mortem examination of the beast that had died showed a rumen full of stalk but no obvious lesions. We then turned our attention to the sick beast which showed s1ight unsteadiness and a nervous aggressive tendency. To examine it more closely, we drove it towards a yard. 'It trotted for about 50 metres, stopped' and fell. The heart stopped, within one minute. The mucous membranes were distinctly brown; the blood was dark but not obviously brown. The diagnosis of nitrate poisoning seemed the most likely. Samples of the stalk taken from the paddock revealed toxic levels of nitrate. We feel in this' practice we may have missed the significance of the stalk of this weed in two previous cases of poisoning. Both of these were on crops that 'contained a lot of redroot, and cattle had been left on a break for an extra day, thus grazing stalk. In one of these cases we had the crop tested fo,r nitrates with negative results, but omitted to send any of the weed stalks. Although not a common poison,}t may not be as rare as records may suggest.
R. H. DUCKWORTH Wanganui Veterinary Club, P.O. Box 612, Wanganui. April 8, 1975.