Avoiding grass-seed contamination of carcases

More than one-quarter of all direct consignment lines of sheep slaughtered in Victoria are reported to have grass-seed contamination by the National Sheep Health Monitoring Project (Figure 1).

From 2009 to 2014, grass-seed contamination affected 29 per cent of lines of adult sheep and 11 per cent of lines of lambs inspected.

 Bar graph with the grass-seed prevalence in sheep less than 2 years and more than 2 years of age along the x-axis and the number of lines along the y-axis.

Young sheep with grass seeds stuck in the fold of skin under the chin above the fleece line Meat & Livestock Australia (MLA) estimates that grass-seed contamination costs around $1.50 per kg carcase weight in downgraded value and extra labour costs.

Abattoirs put effort into ensuring that they supply a quality product. The detection of one grass seed on the surface of a cut of Australian meat in the United States would close that export market.

At the farm level, grass seeds stick in the fleece and work their way into the skin, causing irritation to sheep. In severe cases, they can make the animal reluctant to move, and predispose them to infection, irritation and production losses (Figure 2).

The usual culprits are barley grass, brome grass, silver grass or spear grass — species that are found in pastures across south-eastern Australia (Figure 3). The worst cases of carcase contamination in Victoria occur in lines from the annual pasture sheep production areas, in the north and west (Figure 4).

Map of Victoria showing the distribution of grass-seed contaminated sheep - mostly prevalent in the west of the state.
Map of Victoria showing lines with 30% contamination - most prevalent in the far west of the state.

Figure 5 shows the proportion of lines with severe grass-seed contamination in 2009 to 2014. This illustrates that:

  • lambs are less likely to have grass-seed contamination, as they have had less time to accumulate seeds
  • seasonal conditions can make the problem far worse — the wet summers of 2009 to 2010 and 2010 to 2011 provided ideal conditions for grassy weeds to proliferate in pastures.

Line graph with 2 lines (adults and lambs) with percentage of lines with high prevalence of contamination on the y axis and the year (2009 to 2014) on the x axis.

Prevention of grass-seed infestation in sheep is far more effective than a cure. A significant amount of research has been conducted over many years, and has provided information, training programs and risk assessment tools for farmers. MLA has information on how to incorporate management programs for grassy weeds that will decrease the likelihood of contamination. This information and the 'Winning against seeds' booklet are available to help you manage your properties and livestock to minimise the costly and often painful impact of grass seeds on lamb and sheep carcases.

hanging trimmed sheep carcases

The department is currently working with industry to improve systems to assess grass-seed contamination in lamb carcases, to lead to better feedback to producers about the issue.

Recommended strategies to minimise the risk of carcase contamination by grass seeds include a combination of:

  • grazing management, including altering grazing rotations and stocking density
  • agronomic management through pasture manipulation, fodder conservation and sowing fodder crops
  • stock management changes, including altering the time of shearing or lambing, and using containment feeding areas
  • altering marketing by changing sale time or producing store lambs.

Further advice is available from MLA.

Page last updated: 03 Jul 2020