by Roger Martyn

Introduction

Ryegrass staggers is a disease of grazing animals that affects nerves and muscles and can result in spasms, loss of muscle control and paralysis.

Ryegrass staggers is not to be confused with grass tetany, which display similar symptoms in grazing animals but is caused through lack of magnesium (or excesses of elements that suppress magnesium such as potassium and high nitrates) in the grazing animals diet, and is often associated with low sunshine, cool, and wet conditions. Perrenial Ryegrass staggers is associated more with hot summer conditions.

Ryegrass staggers is caused by toxins produced by a naturally occurring fungus called an endophyte that infects the lower parts and seeds of most perennial ryegrasses and tall fescues in summer. The presence of this fungus and the toxins produced are favourable to these grass plants as they afford a natural protection against a wide range of insect pests to the plants but these same toxins can adversely affect grazing animals such as sheep cattle, horses, deer and alpaca when they are made to graze the affected pastures to low pasture height levels.

Animals with symptoms are will be more flighty, will tremor and stagger and fall into drains, against fences and gates, especially when being moved. They will often seek water in order to cool their lower legs and feet, which tend to swell and get hot. Cattle can often be found standing in troughs, and stock losses due to drowning in dams, creeks and swamps can readily occur as the stock are considerably weakened, less co-ordinated and less able to extract themselves from trouble when affected.

Even when no symptoms are showing, pasture consumption and production can be reduced, because animals dislike endophyte infected pastures, so eat less. High endophyte intakes are often associated with an increased incidence of dags on sheep and loose faeces in general, a sure sign that feed conversion is not at its best.

There are endophyte free perennial ryegrasses and fescues, but they tend to be less drought tolerant.

Selenium supplied to heifers and cows has stopped perennial ryegrass staggers within days. Repeat doses have sometimes cured bad cases in a week.

Management

• Any condition which slows pasture growth or shocks perennial ryegrass encourages perennial ryegrass staggers.
• Animal management should encourage green growing pastures with clover, not ungrazed stemmy perennial ryegrass.
• Rotate stock rather than set stock, and try to grow more species than just perennial ryegrass.
• Avoid moving affected stock (except slowly to fresh pastures), and avoid mustering and yarding.
• Selenium supplied to heifers and cows has stopped perennial ryegrass staggers within days. Repeat doses have sometimes cured bad cases in a week.
• Keeping soils moist by encouraging earthworms and a thick growing and dense pasture sward helps.
• Keeping pastures green and growing, through correct liming, fertilising and by encouraging the establishment of winter ryegrasses as well as clovers, and by rotationally grazing leafy perennial ryegrass.

If perennial ryegrass staggers is an ongoing problem every year, consider planting mid and late summer crops such as turnips to supplement the animals diet so diluting the endophyte effect in the diet while also allowing the animal to avoid grazing the pastures down too hard by being able to move them onto the crop to eat and stay the rest of the day. Use the crop as a part of a farm pasture renewal program to introduce other alternative pasture species, such as fescue triple mixes (improved fescues, cocksfoot, phalaris, praire grass, chicory, plantaina, clovers etc) most of which have low or nil endophyte content yet are sufficiently insect tolerant or to introduced modified endophyte forms of perrenial ryes and fescue which are now commercially available.

Set stocking on stemmy or stressed high endophyte perennial ryegrasses and fescues will increase animals uptake of endophyte as will spraying with fungicides and / or weed herbicides increase increase the levels of endophyte within the plants.

Endophyte levels increases more on perennial ryegrasses with a high nitrogen content, so avoid using artificial N, especially prior to summer. Applying N to pastures at any time decreases the clover content (except on new grasses prior to the clover establishing and producing N), which in turn can result in a higher percentage of perennial ryegrass and endophyte within the pasture sward.

Because endophyte is necessary to reduce damage by insects like Argentine stem weevil, black beetle, pasture mealy bug and root aphid and to give heat and drought resistance, it is important to use only perennial ryegrasses with endophyte.

Fortunately there are now commercially available rye grass and fescue grass varieties where plant breeders have been able to introduce modified endophyte into grass varieties so that the endophyte toxins that afford resistance to insect attack remain while those which causes animal health problems are no longer present. Trials show better animal production/performance while maintaining pasture persistence similar to standard endophyte. It would be beneficial to take the time to match varieties that best suit your particular growing environment and likely insect pests.

Care should be taken to avoid losing the endophyte. Fungicides kill them, as does storing for seed for too long, especially in a hot building. All seeds should be stored in cool places.

Endophyte can be measured in seeds, so levels in perennial ryegrass can be checked before buying seed.