Reduced risk of acute poisoning in Australian cattle from used motor oils after introduction of lead-free petrol.

Lead (Pb) poisoning of cattle has been relatively common in Australia and sump oil has been identified as an important cause of Pb toxicity for cattle because they seem to have a tendency to drink it. Lead-free petrol has been available in Australia since 1975, so the aim of this study was to assess the current risk to cattle from drinking used automotive oils. Sump or gear box oil was collected from 56 vehicles being serviced. The low levels of Pb found suggest that the removal of leaded petrol from the Australian market as a public health measure has benefited cattle by eliminating the risk of acute poisoning from used engine oil.

Cyanide poisoning in cattle from Dysphania glomulifera (red crumbweed): using the internet for rapid plant identification and diagnostic advice.

A 300-strong Angus-Brahman cattle herd near Springsure, central Queensland, was being fed Acacia shirleyi (lancewood) browse during drought and crossed a 5-hectare, previously burnt area with an almost pure growth of Dysphania glomulifera subspecies glomulifera (red crumbweed) on their way to drinking water. Forty cows died of cyanide poisoning over 2 days before further access to the plant was prevented. A digital image of a plant specimen made on a flat-bed scanner and transmitted by email was used to identify D glomulifera. Specific advice on the plant's poisonous properties and management of the case was then provided by email within 2 hours of an initial telephone call by the field veterinarian to the laboratory some 600 km away. The conventional method using physical transport of a pressed dried plant specimen to confirm the identification took 5 days. D glomulifera was identified in the rumen of one of two cows necropsied. The cyanogenic potential of D glomulifera measured 4 days after collection from the site of cattle deaths was 18,600 mg HCN/kg in dry matter. The lethal dose of D glomulifera for a 420 kg cow was estimated as 150 to 190 g wet weight. The plant also contained 4.8% KNO3 equivalent in dry matter, but nitrate-nitrite poisoning was not involved in the deaths.

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.

Studies on the pathogenesis of bovine ephemeral fever. IV: A comparison with the inflammatory events in milk fever of cattle.

The study of ephemeral fever in cattle has defined a range of haematological and biochemical changes in blood which are characteristic of an inflammatory response. One of the clinical signs of ephemeral fever, a temporary paralysis reversible by treatment with calcium borogluconate, is similar to that in milk fever (parturient paresis), a disease of multiparous dairy cows. Three separate groups of cows were studied. Four multiparous cows were observed and sampled repeatedly during calving, three similar cows and one cow calving for the first time in a dairy herd were sampled daily before and after calving; and, in other dairy herds, seven cows with milk fever were sampled during illness. One of the cows under repeated observation during calving developed milk fever. The results showed that all the inflammatory indicators in blood were present in the multiparous cows at calving and that these were essentially similar to those established in ephemeral fever. The similarities in the four cows sampled repeatedly during the periparturient period were: a rectal temperature rise of 1 to 1.2 degrees C; rise in circulating neutrophils to peaks between 5700 and 11200 l-6; disappearance of eosinophils for 1 day; hypocalcaemia (plasma Ca < 2.0 mM l-1); fall of plasma zinc to low levels immediately after calving (plasma Zn < 500 micrograms l-1); fall of inorganic phosphate (plasma P < 0.9 mM l-1); rises in copper (plasma Cu > 1000 micrograms l-1) and plasma fibrin to > 8.75 g l-1. Plasma glucose peaked at calving between 5.7 and 8.9 mM l-1 then fell to levels ranging between 3.4 and 3.8 mM l-1. Plasma iron rose in one cow to 1220 micrograms l-1, was unchanged in one cow and fell in the other two to 440 and 860 micrograms l-1 respectively. The three multiparous cows which were sampled daily and calved normally showed similar haematological, macro and micromineral changes and fibrin response as did the seven milk fever cases. In the periparturient period, milk fever cows differed from multiparous cows calving normally, in degree but not in kind, of inflammatory response. It is postulated that an inflammatory event occurs in the periparturient period of multiparous cows which partially accounts for the falls in plasma calcium. This can precipitate a paralysis and other hypocalcaemic signs similar to that seen in acute ephemeral fever.