May 27, 2011

 

Australian dairy herds are threatened by new diseases

 

 

Four cattle diseases are surfacing to affect Australian dairy herds, according to one of Australia's top cattle veterinary experts.

 

Cattle veterinarian, Dr Rob Bonanno, focused on four emerging cattle diseases when he addressed the Australian Veterinary Association's Annual Conference in Adelaide last week.

 

"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," Bonanno said.

 

"Many of these new cattle diseases have become increasingly common due to the extremely wet weather conditions we have been having in recent months."

 

A trend towards larger herd sizes is also correlated with many emerging diseases of importance.

 

The cause of Acute Bovine Liver Disease (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).

 

Bonanno said removal of animals from affected paddocks when the first signs appeared was critical to prevent new cases and limit the toxic damage to mildly affected animals and aggressive early treatment could save many cows.

 

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," Bonanno said.

 

"Other risk factors also include large herd sizes which are defined by more than 500 head, newly introduced cattle, and larger breeds of cattle such as Holsteins."

 

Haemorrhagic Bowel Syndrome (HBS) 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 Zinc toxicity is 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 stocks often receive a relatively higher dose and may be the group that is affected the most.