Four emerging cattle diseases are threatening Australian dairy herds according to one of Australia’s top cattle veterinary experts.
Cattle veterinarian Dr Rob Bonanno told the Australian Veterinary Association’s Annual Conference that these four new diseases are: a fatal cattle liver disease thought to be caused by an annual grass and a plant fungus; lameness caused by hairy heel warts; haemorrhagic bowel syndrome; and the growing issue of zinc toxicity.
“Many of these new cattle diseases have become increasingly common due to the extremely wet weather conditions we have been having in recent months,” said Dr Bonanno. “A trend towards larger herd sizes is also correlated with many emerging diseases of importance.”
Dr Bonanno said that removal of animals from affected paddocks when the first signs appear is critical to prevent new cases and limit the toxic damage to mildly affected animals; aggressive early treatment can save many cows.
“This disease has become one of the leading causes of lameness in confinement dairy herds in North America and Europe, and is being diagnosed increasingly in Australia, especially on farms that have adopted intensive systems of production,” said Dr Bonanno.
The disease is caused by exposure of the feet to a slurry of manure resulting from poor drainage or poor hygiene protocols, damage to the feet caused by rough flooring or poor pathways, wear damage due to sand or poor tracks, and maceration of the skin due to wet muddy conditions. “With the particularly wet weather in recent months and a move away from drought conditions, the presence of muddy laneways, loafing areas or feed pads, digital dermatitis has become a more frequent issue,” said Dr Bonanno. “Other risk factors also include large herd sizes (especially over 500 head), newly introduced cattle, and larger breeds of cattle such as Holsteins,” he said.
This is being reported with increasing frequency in lactating dairy cattle in recent years. This sometimes presents as a cause of sudden death, but also sudden milk drop, abdominal pain and loss of appetite. The exact cause of HBS is not known, however risk factors may include rumen and post rumen acidosis, fungal infections such as aspergillus, or clostridial bacterial infections.
Although rarely seen in Australia, zinc toxicity can be a symptom of use of excessive supplementation in the diet to prevent facial eczema or zinc sulphate contamination of feed. Signs can include anorexia, diarrhoea, chronic constipation and reduced milk yields. More severe signs are heart problems and seizures, ill thrift and death. Young stock often receive a relatively higher dose and may be the group that is worst affected.
The cause of ABLD, which has been recorded in Western Australia, South Australia, Tasmania and Victoria, is not clear but it is associated with warm humid conditions and the presence of an annual grass called Rough Dog’s Tail which has a specific fungal growth. Symptoms of ABLD can include sudden death, severe milk drop, acute abdominal pain and sensitivity to sunlight with marked photosensitisation (sunburn).
If you have spotted any unusual signs in your cattle please call the Emergency Animal Disease Watch Hotline on 1800 675 888.