Why would scientists use sheep if they want to find out how ryegrass endophyte affects dairy cows?
Agriseeds science manager Colin Eady says there are two good reasons: “Sheep are more sensitive to ryegrass staggers than cattle, and because they are smaller, higher numbers can be run on the same area, providing more robust statistical data. So if it is safe for the sheep, it is more than likely to be safe for the cow.”
He’s talking about endophyte animal safety trials being run this summer.
As in previous years, these aim to test new grass-endophyte combinations under ideal conditions for ryegrass staggers. With careful supervision, separate mobs of lambs will be grazed for eight weeks at the height of summer on pure swards of perennial ryegrass deliberately allowed to become overgrown and stalky to maximise production of the endophytes’ chemical defences.
As the trial progresses, the lambs will graze the swards right down toward the base of the plant where most endophyte chemicals are produced. This tries to mimic a ‘worst case’ exposure of the lambs to the chemicals.
Those which succumb to staggers, or a decline in body condition are removed as required and the grass-endophyte combination they were grazed on is not progressed.
New animal safe grass/endophyte combinations that do not cause issues are progressed and the information used to further improve Agriseeds’ safety data.