Farm Tech

In The Paddock
Seasonal sheep and cattle management tips – February 2003

Beating endophytes – Grazing management and pasture renewal are the best solutions

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Key points

• Absorbent yeast and clay compounds may reduce ryegrass staggers and improve stock health.
• Reducing intake of toxic ryegrass by grazing management or offering supplements, crops etc is beneficial.
• Replace toxic ryegrass with AR1 ryegrass or a similar safe endophyte cultivar where possible.
• Spraying/cropping or double spray/fallow reduces toxic ryegrass seed in the soil and ensures a safe pure sward is established. This could take two years.
• Prevent the invasion of wild-type seed via hay/silage, dung, fleeces and machinery.
• Selection for animal resistance to staggers may be a good long-term strategy.

The endophyte fungi which grow inside ryegrass plants have both beneficial and negative effects. The alkaloids produced by the fungi protect the grass from insect attack, but some cause ryegrass staggers (RGS) and heat stress.

While prevention is the best way to deal with these conditions, a number of potential remedies are promoted as offering a cure.

Absorbent compounds based on yeast cell wall extracts or zeolite and bentonite clays have looked promising in lab studies, but have yet to be fully proven in practice. Some farmers claim to have had good results from their use.

Other remedies such as cider vinegar, potassium chloride/magnesium sulphate mixture, Nutrimol, seaweed extract and trace element/vitamin E supplements are also being used to treat animals for RGS, but generally with low success rates.

Grazing management

Eliminating or reducing the intake of the toxic parts of perennial ryegrass which contain the wild endophyte is the only sure method of prevention.

This can be done by diluting the ryegrass intake with supplements, or by shifting the animals onto a ryegrass-free pasture or crop. Alternative feeds, such as hay, silage, grain and forage crops reduce intake of fungal toxins.

Ryegrass hay may contain the toxins, so lucerne or clover hay is preferred. Silage is likely to be a safer option than hay as it is normally made early when toxin levels are low.

Grazing management can also be used to minimise the problem.

Because the endophyte toxin is concentrated in the leaf, sheaths, stems and seedhead, grazing management must aim to minimise the intake of these parts of the plant. Topping or cross-grazing with less susceptible animals such as adult cattle to decrease the amount of seedhead will help.

Rapid rotations are the key. Pastures should not be grazed below around 3 cm height. Spelling between grazings to allow regrowth, and grazing regularly enough to prevent growth of seedheads, is particularly important in December/January. Where this is not achievable over the whole farm, it may be possible to develop safe areas.

Replacing toxic ryegrasses

Where land can be cultivated, pasture renovation using safe endophyte species will often be the most effective solution.

AR1, a recently developed ryegrass containing a safe endophyte, provides another solution. For areas like Northland where black beetle, which attacks AR1 ryegrass, is common, other safe-endophyte ryegrasses may be available. Consult your local seed merchant for advice.

Good preparation of the paddock is vital before sowing a safe endophyte species. This means eliminating the existing ryegrass in the pasture either with a double cropping programme or double spray.

In summer dry environments where there are high levels of ryegrass seed in the soil, two summers should elapse between removal of the last pasture and sowing of the new one. All existing vegetative ryegrass plants should be destroyed either by repeated cultivations and/or herbicides.

A seedbed that favours rapid establishment of the sown pasture (e.g. fertile, moist, fine, weed-free) will reduce contamination of the new pasture.

Dexcel has studied how pre-sowing management and establishment method influences the contamination of a newly sown AR1 ryegrass with wild endophyte. In their study, hay, silage, grazing, grazing/topping and a turnip crop pre-sowing resulted in 2555, 747, 348, 391 and 25 wild type seeds/m², respectively, remaining on the soil surface after natural re-seeding.

This illustrates the importance of having a crop in the rotation to reduce the number of wild-type seeds remaining in the soil. Two such cropping cycles would reduce seed levels even further.

Spray/cultivation and double-spray/fallow reduced contamination with volunteer ryegrass plants to 8 and 34 plants/m², respectively, compared to direct-drilling AR1 seed into hard-grazed existing pasture (581 plants/m²).

While the spray/cropping or double spray methods are recommended, there are concerns about how successful they are on hill country. However, on-farm work by the Northern Sheep Council, Ballance Agri-nutrients, C Alma Baker Trust, Nufarm NZ and Wrightson Seeds in the northern North Island has shown the spraying/cropping or double-spray/fallow regime using a helicopter can be quite successful.

The invasion of new AR1 pastures by wild-type ryegrass is always a risk. To reduce the risk, prevent seed entering via dung, in fleeces, hay/silage, sown seed or machinery. The grazing rotation is important. Avoid grazing wild-type ryegrass pasture, especially if it is seeding, just before grazing new AR1 pasture.

Genetic selection offers a potential long-term solution to RGS.

During a six year trial, AgResearch Ruakura selected for resistance or susceptibility to RGS in sheep. At the end of the trial, there was a 24 per cent difference in the incidence of RGS between the two lines. Unfortunately, resistant rams are not yet commercially available, but genetic selection is a good long-term protection policy.

More information

Ryegrass endophyte – an up-to-date review of its effects, WoolPro 2001.

In The Paddock, January 2003. Ryegrass endophytes – both friend and enemy.

Meat NZ R&D Briefs – No 17 and No 45.

Your local farm consultant can provide useful advice about reducing the impact of endophtyes. Alternatively, contact your local Meat & Wool Innovation extension specialist: