By Charlotte Westwood, Veterinary Nutritionist, PGG Wrightson Seeds
Stock got the wobbles?
Ryegrass staggers cause sheep, cattle, deer (and horses, alpacas and goats) to “get the shakes” (tremors), a stumbling staggered gait and incoordination. Stock rarely die from direct effects of ryegrass staggers, but fatalities can occur if animals fall into water troughs, down gullies or become cast under electric fences etc. From a management point of view, stock with severe ryegrass staggers can prove almost impossible to manoeuvre – for instance, yarding or even just moving stock from one paddock to another. What are ryegrass staggers and what preventative measures can we take? How do we manage stock affected by staggers?
The following overview provides general information on ryegrass staggers. As always, your veterinarian remains your number one ‘go-to’ person for advice specific to your own stock.
What is the cause of ryegrass staggers?
Ryegrass staggers can occur in animals grazing perennial or long rotation hybrid ryegrasses that contain a seed-borne endophytic fungus, Neotyphodium lolii. The ryegrass endophyte association is an important one. Ryegrass persistence is greatly improved with endophyte alkaloids which deliver protection to the plant against a range of insect pests.
Standard ryegrass endophyte (also called “wild type”) produces several endophyte alkaloids, including peramine, which helps plant persistence. Another alkaloid, Lolitrem B, is a neurotoxin responsible for ryegrass staggers.
What are the symptoms of ryegrass staggers and what time of year poses a higher risk??
Symptoms of ryegrass staggers are often noticed when walking amongst stock or shifting them into another paddock. Left alone, often there’s not much to see – stock appear fine or at worst, show a bit of a head tremor. Moving stock increases the risk of making the tremors worse, animals may stumble and stagger, unable to walk well. Convulsions might be seen; animals may collapse and struggle to get back up. For dairy cattle, cows can appear ‘grumpier’ than usual in the dairy shed, being jumpy, twitchy and over-reactive to stimuli such as loud noises, bikes and dogs.
Summer and autumn pose a higher risk for ryegrass staggers. With that said, a late spring flush of seedhead production in ryegrass increases the level of Lolitrem B consumed by stock, which is a leading cause of ryegrass staggers. Seedheads and stem contain a high concentration of Lolitrem B. Caution is also required around grazing sheath at the base of the plant, as the risk of ryegrass staggers increases as stock graze down to low post-grazing residuals. The leaf of ryegrass plants contains relatively low levels of endophyte alkaloids. Ryegrass staggers is rarely seen during winter and early to mid-spring.
What increases the risk of ryegrass staggers?
- Most cases arise from stock grazing old pastures that have not been regrassed in a long time or paddocks which have been regrassed with older ryegrass cultivars infected with standard endophyte. However, cases are occasionally seen on paddocks recently regrassed with modern, novel ryegrass cultivars which have reverted back to older, standard endophyte infected ryegrasses.
- Low post-grazing residuals pose a high risk – when stock graze into the bottom 2.5cm of the ryegrass pasture (where Lolitrem B is more concentrated)
- Ryegrass staggers are more likely in ryegrass-dominant pasture mixes with few clovers, herbs or non-endophyte infected grasses present to ‘dilute’ stock intake of Lolitrem B.
- Seedhead-dominant ryegrass pastures increase the risk of standard endophyte ryegrasses causing ryegrass staggers compared to leafy ryegrass pastures.
- Ryegrass staggers occur most often in summer and early autumn months. During summer conditions the endophytic fungal mycelium (that release Lolitrem B) extends up into the leaf sheath. In contrast, during winter and early spring, the myeceliae shrink back down into the base of the plant. Endophyte hyphal counts and Lolitrem B production are close to zero during colder winter and early spring months.
Why don’t we see as many cases of ryegrass staggers as we used to?
Very few modern ryegrass cultivars contain standard-type endophyte responsible for producing Lolitrem B. Novel endophytes such as AR1 and the NEA endophytes can contain minimal levels of Lolitrem B or it is otherwise completely absent. Ryegrass staggers can sometimes be seen in sheep (and very occasionally cattle) grazing ryegrasses infected with AR37 endophyte due to the presence of epoxy-janthitrems, chemicals closely related to Lolitrem B. Compared with clinical signs associated with Lolitrem B, cases of epoxy-janthitrem associated ryegrass staggers are usually relatively milder and resolve more quickly once stock are removed from ryegrass pastures.
How can we help stock with ryegrass staggers?
- Leave stock alone. Left alone, stock with ryegrass staggers manage to ‘mostly’ do fine – it is the stress of yarding and shifting animals that sets off the clinical signs of ryegrass staggers. This is not a practical solution as we still need to handle animals to move them onto new paddocks, drenching etc.
- Shift out of paddock. Moving stock out of the paddock responsible for ryegrass staggers is a good plan. The aim is to allow plenty of time to quietly move stock. Don’t bring in dogs or bikes/quads etc, instead get some patient, gentle people to help very quietly and slowly move stock out of the paddock.
- Non-ryegrass forages. Choose an alternative paddock to move affected stock into – ideally one that has pasture that has been recently regrassed with nil-endophyte ryegrasses (such as endophyte-free Italian ryegrasses), modern novel ryegrass endophytes that do not produce Lolitrem B and/or pastures containing more non-ryegrass species such as clovers or herbs (including plantain or chicory). Summer crops are also a good option (brassicas such as raphanobrassica, or chicory or plantain), because crops are completely free of endophyte alkaloids.
- Keep post-grazing residuals high. If all paddocks are standard-type endophyte and/or ryegrass dominant pastures, then move stock into a paddock with a large pasture mass and keep post-grazing residuals high to prevent stock grazing into the base of the pasture where the Lolitrem B levels are more concentrated.
- Feed out supplements. If symptoms of ryegrass staggers are severe and you are struggling to move stock, consider feeding out baleage or silage to animals. However, check your supplement type as hay/silage made from an older ryegrass-dominant paddock and containing a lot of seedhead may contain high levels of Lolitrem B. Lucerne hay or silage would be a great alternative.
- “Silver bullet treatments”? Useful animal treatments for affected animals are few and far between. Interesting work from researchers at Charles Stuart University, Australia, suggested oral doses of potassium bromide might help lambs recover from staggers, however exact dose rates that safely reduce staggers symptoms while not harming the lambs remain elusive.