Can cattle spread giant rats tail grass seed (Sporobolus pyramidalis) in their faeces?

Abstract

Giant rats tail grass (GRT) (Sporobolus pyramidalis and S. natalensis) is an unpalatable and aggressive weed of pastures that has the potential to infest large areas of northern Australia. One possible means of spread is in the manure of cattle. In a pen trial where cattle were fed one dose of a known quantity of GRT seed, three questions were posed: (i) does GRT seed pass through the gut of cattle? (ii) if so, is the seed viable?, and (iii) how long does it take for seed to pass through? Forty one percent of the seed fed to the cattle was excreted. Seventy nine percent of that seed remained viable giving a total of 28% of seed fed to cattle passing through unharmed. Greater than 94% of excreted seed was excreted on days 2 and 3 with none being detected in sub-samples of manure after day 4. The practical implications are that, once eaten, GRT seed can be spread in the manure of cattle. As a precautionary measure, cattle being moved from GRT infested areas to clean areas should be detained on a diet free of GRT seed for at least 4 days before release.