Page 22 - ACV Journal DECEMBER 2015
P. 22
Scientific 3
WATER (SALT) TOXICITY
IN LOST CATTLE
Megan Davies, DV, North West LLS Narrabri
12
4
1. Deceased steer found near the water trough. Note the bleeding from the nose - likely due to intravascular haemolysis. 2. Liver of euthanased steer with rounded edges and pale tan “nutmeg”.
3. Kidney of euthanased steer. Note the dark purple colour and no clear demarcation between the cortex and the medulla. pattern throughout surface. 4. Recumbent steer prior to euthanasia.
District veterinarians were initially called to investigate the deaths of 6 between the medulla and cortex. The abomasal mucosa was red and
cattle in a 400Ha paddock in North Western NSW in August 2015. congested. The rostral half of the cerebrum was bilaterally grey, while
The mob of 270 Angus x steers were grazing native pasture, largely the vertebral canal contained a large amount of clear fluid with a jelly-like
wild turnip, burr medic and galvanized burr. Some thick stands of turnip consistency. Broadly, the steer was a “dark cutter”, with dark red / purple
were up to 2m in height. The cattle had been moved to the paddock 8 skeletal musculature throughout the body.
days prior from a similar property approx 100km away. Since their arrival
they had lost condition, become lethargic, and had a “hollowed out” Histopathological testing of samples sent to EMAI (Elizabeth Macarthur
appearance. The deceased cattle were spread throughout the paddock, Agricultural Institute) showed no evidence of liver pathology. The kidneys
and were noted to have a bloody nasal discharge. They were presumed showed evidence of reduced renal perfusion, while the vaculolation of
to have died over a period of 48 hours. All had been recently vaccinated the cortex of the cerebrum was consistent with cerebral oedema.
with 5-in-1 clostridial vaccines, and had been recently drenched.
Water salinity testing showed the salinity of the trough water was within
On finding the deceased cattle, the caretaker had cleaned out the water recommended safe limits (400uS/cm, recommended to be <1600uS/cm).
trough, after which the cattle swarmed around the trough, drinking large
amounts of water. Three more animals died soon after near the trough. The combination of hypernatramia and cerebral oedema, added to the
The caretaker then let the cattle into the adjoining paddock where there history of sudden intake of large volumes of water led to a diagnosis
was a dam, fed by the same bore as the trough. The cattle gathered of water intoxication. This condition occurs after a period of water
around the dam, several immersing themselves, and a further three deprivation causes a buildup of extracellular sodium and movement
animals died in the dam. of fluid out of the central nervous system (CNS). A sudden influx of
water causes fluid to move rapidly back into the CNS, causing cerebral
On arrival at the property, initial field investigations involved testing for oedema. The sudden influx of fluid also causes red cells to burst,
Anthrax (negative) and Nitrate / nitrates (negative). Aqueous humour causing intravascular haemolysis – explaining the condition of the blood
was collected from the eye of one deceased animal, and a full post samples on arrival at the lab.
mortem was performed on a recumbent animal that was euthanased.
Initial differential diagnoses included polioencephalomalacia, salt toxicity Further discussion with the caretaker of these cattle revealed that they had
and other toxicities including plants. not been shown the location of the water trough when first moved into the
paddock. Owing to its large size, and the volume and height of vegetation
Testing of the aqueous humour and serum from the euthanased steer present, it is likely the cattle got lost in the paddock, and were unable to find
revealed both had very high sodium levels (180mmolL and 158mmol/L the single water source. Consequently, the early deaths were likely due to
respectively (normal range 135-152mmol/L). Unfortunately, biochemical water deprivation, while the later deaths were likely a result of sudden over
analysis of the blood from the euthanased steer was not possible as hydration after the water source was discovered by the cattle.
the samples were severely haemolysed on arrival at the laboratory. The
post mortem revealed a swollen, friable liver, with a nutmeg pattern on The surviving cattle remained in the paddock with the dam, where they
the surface. The kidneys were dark purple, with no clear demarcation recovered slowly over the next week, with a further 2 deaths noted. A
total of 15 cattle died during this episode.
22 The Australian Cattle Veterinarian | volume 77 | December 2015 www.ava.com.au/cattle
