Lift in grass seed contamination thorn in side for sheep industry

The number of sheep carcasses impaired by grass seed is increasing but some areas are worse than others. See which states are most at risk.

A lift in grass seed contamination was one of the key findings in the monitoring of sheep animal health in abattoirs.

And while overall levels across all carcasses remain relatively low, the surveillance work has show there are hot spots where more than 10 per cent of sheep are showing seed contamination issues.

The National Sheep Health Monitoring Project is an annual assessment of sheep carcasses, and involves abattoirs in Victoria (Ararat, Geelong and Brooklyn); NSW (Cowra, Dubbo, Gundagai and Tamworth); South Australia (Lobethal); Tasmania (Cressy), and Western Australia (Narrikup).

Grass seed infestation in sheep.

A map showing contamination by local government areas showed key Victorian lamb production areas had zero issues with grass seed contamination in carcasses.

But the news was not so good for NSW, with some local government areas having levels of more than 10 per cent of carcasses with seed contamination.

Of the 9.8 million carcasses monitored, 103,455 or 1.1 per cent showed grass seed contamination, but when animals younger than two years were isolated, that level rose to 1.4 per cent.

The states to show the biggest lift in grass seed contamination were Tasmania, up 1 per cent, and South Australia, up 3 per cent.

“The percentage of impacted PICs is relatively low compared to other conditions, which suggests that grass seeds tend to be concentrated in certain areas, rather than being widespread over many PICs across the state,” the report said.

Results from the annual national survey for 2022-23, which have just been released, show grass seed issues in carcasses have been steadily rising during the past three years.

“Grass seeds embedded in the carcass due to spear, brome, barley, silver and Chilean needle grasses cause weaner ill thrift, infections and/or death, reduction in wool production and wool value,” the report said.

“Grass seeds also cause trimming of the carcass and a decrease in meat and skin value.”

The monitoring found the total number of sheep carcasses affected by grass seeds lifted by 0.6 per cent in 2022-23 compared to the previous financial year.

The project started in 2007 and was created to monitor sheep carcasses for various animal health diseases.

In the past financial year, there was a rise in the number of sheep inspected as well as a lift in the source properties.

There were 9.8 million sheep inspected over the 12-month period, up from 7.8 million in 2021-2022, while the sources of those sheep (individual property identification codes) rose to 10,255.

While there was a lift in grass seed issues, two other conditions were found more often.

Of the carcasses which were assessed, bladder worm proved to be the most prevalent condition at 2.9 per cent of all inspected sheep in Australia, while pleurisy impacted 1.8 per cent of carcasses.