In June 2000 a dairy farmer at Burrumbuttock reported a problem with his weaned dairy calves. The property is 432hectares and run primarily as a dairy.
Affected animals were first noticed about end of April (2 months prior). He reported variable neurological signs and 2 deaths. The owner suspected a mineral deficiency. The calves were grazing on phalaris dominant pasture. In the affected group there were 36 weaner calves around 10 months old, of which 6 had been affected (2 deaths, 4 neurological signs).
There was some scant standing dry feed of poor quality and variable amounts of green phalaris regrowth had been grazed all following ‘autumn break’ rains. The calves were supplemented with 4 kg grain per head every second day and had fescue hay available in a self feeder at all times.
Some of these calves were destined to be replacement heifers. These calves had been grazing this pasture since weaning about 5 months beforehand.
The affected calves were not losing condition and appeared bright and alert.
Variable neurological signs were seen — all had a wide base stance in the front limbs. Some had difficulty getting up. Some had been seen grazing on their knees. There was variable posterior paresis — but that was generally quite mild. Some calves occasionally showed a fine head tremor.
The most severely affected calf showed knuckling of all fetlock joints. This calf also had a constant fine head tremor. This animal had lost some weight and was now almost totally recumbent. The most severely affected calf was euthanized.
No significant findings reported. Pigment in the brain was looked for but not seen grossly.
The brain was examined on histopathology and sections taken at the level of the colliculus and obex revealed pigment within the neurones. The type and distribution was typical of that seen in phalaris staggers.
The calves were removed from the pasture and pasture renovation was planned to reduce phalaris dominance
The calves were to be monitored with the expectation that there may be some further deterioration over the next few months immediately after the removal from the toxin. It was not expected that the affected animals would completely return to normal. They were given a guarded prognosis and it was recommended that affected animals not be kept as milkers as periods of stress may increase symptoms and affected animals moving over slippery concrete would be more at risk of injury. It was recommended they be culled direct to slaughter to reduce stress rather than selling through the yards.
There were no more cases seen that deteriorated to the point of requiring euthanasia or other intervention.