Nitrate-nitrite toxicity in cattle and sheep grazing Dactyloctenium radulans (button grass) in stockyards.
Hungry cattle and sheep introduced to stockyards containing a dominant or pure growth of Dactyloctenium radulans (button grass) suffered acute nitrate-nitrite toxicity in four incidents in inland Queensland between 1993 and 2001. Deaths ranged from 16 to 44%. Methaemoglobinaemia was noted at necropsies in all incidents. An aqueous humour sample from one dead steer contained 75 mg nitrate/L and from one dead sheep contained 100 mg nitrate and 50 mg nitrite/L (normal = ca 5 mg nitrate/L). Both lush and dry button grass were toxic. The nitrate content of button grass from within the stockyards ranged from 4.0 to 12.9% as potassium nitrate equivalent in dry matter and from outside the stockyards ranged from <0.2 to 0.4%. These data suggest that urine and faeces in stockyard soil may boost the nitrate content of button grass to a concentration hazardous to hungry ruminants.
McKenzie
R A
RA
Department of Primary Industries, Yeerongpilly Veterinary Laboratory, Animal Research Institute, Locked Mail Bag No 4, Moorooka, Queensland 4105. ross.mckenzie@dpi.qld.gov.au
Rayner
A C
AC
Thompson
G K
GK
Pidgeon
G F
GF
Burren
B R
BR
D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000209:etiology* / Q000401:mortality; D017809:Fatal Outcome; D005260:Female; D008297:Male; D008708:Methemoglobinemia / Q000209:etiology / Q000401:mortality / Q000662:veterinary*; D009566:Nitrates / Q000506:poisoning; D009573:Nitrites / Q000506:poisoning; D010939:Plant Poisoning / Q000401:mortality / Q000662:veterinary*; D006109:Poaceae / Q000506:poisoning*; D011793:Queensland; D012756:Sheep; D012757:Sheep Diseases / Q000209:etiology* / Q000401:mortality
D009566:Nitrates; D009573:Nitrites