After months of dry conditions, recent rains have brought a lush flush of green growth across the region — but along with it comes a hidden danger for livestock - Phalaris toxicity.
Livestock producers are being urged to monitor their animals closely, as grazing on young Phalaris grass, particularly when there is little other feed available, can lead to severe illness or even sudden death.
Phalaris grass is particularly dangerous in its early growth stage — usually the first six weeks.
During this period, the plant contains toxic alkaloids that can trigger Phalaris staggers, a condition affecting coordination and mobility. Another threat, Phalaris sudden death syndrome, arises from high ammonia levels in the animal's system. Sheep are especially vulnerable, while cattle are somewhat less so.
Interestingly, kangaroos also are very susceptible. Numerous cases of Phalaris staggers in kangaroos have recently been seen.
Phalaris staggers may not appear immediately. Symptoms can develop between 10 days and four months after grazing the pasture.
Animals may stagger or stumble, adopt a 'bunny hop' gait, nod their heads, struggle to stand or eat, and lose weight. Some sheep may recover but remain permanently affected.
Sudden death syndrome is far more rapid. Signs, which typically emerge 12 to 36 hours after grazing, include breathing difficulties and blue-coloured gums, often leading to death within hours.
If Phalaris toxicity is suspected, affected animals should be removed slowly but immediately from the pasture to reduce further risk.
Preventive measures include:
Limiting grazing during the first two days to only a few hours per day;
Managing stocking rates carefully; and,
Providing hay before turning stock onto pasture to reduce overeating
In cobalt-deficient areas, cobalt supplementation may help reduce the risk of Phalaris staggers, although it does not prevent sudden death syndrome.
Producers concerned about Phalaris toxicity should contact their local veterinarian, Agriculture Victoria veterinary or animal health officer.