"What do Socrates, Sherlock Holmes & sheep farmers have in common? They have all been affected by alkaloids." A Report on the 2002 Perennial Ryegrass Staggers Epidemic.
Dr Katrina Rainsford B.V.Sc. M.A.C.V.S.
District Veterinary Officer
Pastoral & Veterinary Institute
Department of Natural Resources & Environment
Private Bag 105
Hamilton, Victoria 3300
In: Plant toxins and their effects on animal welfare. Paper presented at the Animal Welfare Centre Scientists' Meeting, 17th May 2002, DPI Werribee, Mickleham Road Attwood, Victoria.
Perennial ryegrass staggers (PRGS) is common throughout the western districts of Victoria where staggers can appear in summer and autumn but deaths are rare. In 2002 reports of horses with perennial ryegrass staggers in January were followed by reports of sheep with PRGS from early February. During March the numbers of properties and the numbers of stock on properties exhibiting the syndrome increased. In April it became apparent that the common condition causing few losses and minor stock management interruption was more widespread than usual and causing substantial stock deaths and prolonged livestock management problems. A working group of Pastoral & Veterinary Institute scientists was established to respond to the graziers concerns. The group provided extension materials through print and radio outlets, fact sheets to the NRE call centre and producers, set up a monitoring project measuring alkaloids on ten representative farms, and circulated a PRGS producer survey to track the extent of the epidemic and the losses associated with the condition. A local Hamilton district producer survey reported sheep mortality of 4%. Reports from interstate included 10% loss in weaners on Kangaroo Island where diagnosis of the condition is uncommon. Tasmanian and southern Western Australian diary farmers also reported losses particularly in heifers and bull beef operations. The PRGS Survey 2002 will provide a dataset for future research. Perennial Ryegrass Staggers surveys have been received from 257 producers from three states (Victoria, South Australia and Tasmania). 32,000 sheep died on 217 properties surveyed with perennial ryegrass pastures present on the property. Up to 30% mortality occurred in some mobs, with the majority of losses being experienced in weaners. Cattle losses were minimal (0.2%) but up to 2% in some weaner mobs. Most producers reported difficulty in handling cattle, increased injuries when working with affected cattle and suffering delays to marketing.
Perennial ryegrass staggers occurs in sheep, cattle, horses and deer. Alkaloids produced by the endophytes found in perennial ryegrass act as neurotoxins, specifically the tremorgen Lolitrem-B. The vasoconstrictor alkaloid ergovaline is also present in the Lolium perenne endophytes affecting circulation. The ergovaline toxin is associated with increased body temperature, alteration in the production of prolactin and digestion.
The condition is a reversible alkaloid toxicosis. Stock grazing affected pasture can exhibit symptoms after one to two weeks and when removed from the toxic pasture return to normal movement in one to three weeks. Sheep develop a fine head tremor that progresses to nodding, tremble, display incoordination, jerky exaggerated limb movements with a stiff-legged gait. The condition is induced by stimulation like driving the mob, and affected stock can go down on their side with their legs extended. Left alone they can recover, regain their coordination and get up and resume grazing. Appetite is not affected by the condition, with an abundance of ryegrass pasture available stock graze until they unable to graze.
Producers in the Western Districts of Victoria reported cases of perennial ryegrass staggers in early summer with higher than usual October rainfall producing increased growth of perennial ryegrass. February rain provided persistent green ryegrass pasture and a high availability to stock. Many pastures became ryegrass dominant. Stock were grazing toxic pastures from January to June 2002, compared to a seasonal short term autumn occurrence. The impact of the prolonged period of managing toxic pastures has been reduced condition of stock, particularly ewes coming into lambing and weaners. Producers and consultants are recognising the potential illthrift that prolonged exposure to perennial ryegrass endophyte toxins is having on profitability.
Throughout Victorian high rainfall areas there were reports of increased incidence and severity of PRGS. Gippsland graziers reported large losses in sheep, Northern Midland cattle producers experienced significant handling problems with flighty staggering cattle. Tasmanian sheep, dairy and beef producers were affected. Western Australian producers in the Albany district reported significant losses in weaner dairy cattle. South East of SA producers experienced unusual losses in sheep and cattle and reports were received from Kangaroo Island of up to 10% of weaners being lost in affected properties.
This year the accepted occasional inconvenience of a few staggery sheep in the odd mob was replaced by more sheep being affected, for longer, being found down in the paddock and remaining recumbent for longer. Handling individual sheep aggravated the tetanic extension of limbs and sheep were extremely difficult to nurse. A feature of losses this year was the number of reports of sheep drowning in troughs not just dams and drains.
With all species death is usually by misadventure (drowning in troughs, dams and gullies), wasting due to recumbency, starvation and dehydration with many down stock requiring euthanasia. However this year some sheep were found dead overnight when grazing toxic pastures for prolonged periods.
Illthrift and poor growth rates when grazing endophyte infected perennial ryegrass has been suspected and is listed in diseases of uncertain aetiology causing weaner illthrift in Radostits Gay Blood and Hinchcliff ,Veterinary Medicine (9th Edition). Pasture palatability or mycotoxins in the soil or pasture are suspected of causing this seasonal illthrift and reduced weight gains despite an abundance of feed. The toxins also affect the digestive tract and secondary deficiencies in nutrients and trace elements could be anticipated. Producers reported an increase in flystrike and exacerbated foot rot in some flocks.
Cattle grazing toxic pastures commonly tremble, become excitable and erratic to handle, can go down on their brisket and splay their legs out backwards. This year major disruption to management procedures like pregnancy testing, weighing and marketing were recorded along with reports of deaths in water troughs and liquid feeders. Three weaner cattle were reported drowned in one large cattle trough. Both sheep and cattle being mustered for the expanding live export trade were affected by the prolonged perennial ryegrass stagger period with many producers reporting marketing delays and increased rejections prior to shipment.
Horses are reported to exhibit trembling, staggering and incoordination with erratic behaviour when handled. A summary from an equine newsletter reported previously unknown handling difficulties, with the blacksmith's work made more difficult. Few reports on the survey and those PRGS deaths were associated with horses being caught in fences or found down and requiring euthanasia.
Deer are described as demonstrating more exaggerated staggers and incoordination that sheep. The 2002 survey had reports one deer producer reporting losses suspected to be attributed to PRGS with post mortem consistent with PRGS and alkaloid levels present in the faeces and pasture where 40 does and 100 fawns were lost on a perennial rye grass pasture dominant deer farm. Whilst change in climate and managements systems were considered factors in this isolated case pasture samples and faecal samples identified the presence of the endophyte alkaloids ergovaline and lolitrem-B.
Journals report that alpaca are susceptible to perennial ryegrass toxicosis and reports were received of affected animals but no deaths with all recovering.
Hay produced from perennial ryegrass (Lolium perenne) infected with the endophyte (Neotyphodium lolii) which produces alkaloids including Lolitrem-B has been associated with atypical pneumonia and ryegrass staggers in weaned beef calves (North America). Levels of alkaloids can be measured in hay. The samples tested at PVI from a severely affected property produced a low alkaloid level.Producers need to be aware that dry feed and hay can have toxins and tests are available to check.
Current Management Methods
Delay management procedures
Initially this is the preferred management tool. In an average year by leaving stock alone whilst suffering low levels of perennial ryegrass toxin exposure will reduce the number so sheep that go down and require nursing or destruction.
Removing sheep from the toxic pastures can allow detoxification in 5 days. The time for recovery could be proportional to the period of exposure to the pasture toxin. Sheep can still be suffering a loss of condition and illthrift despite the receding tremor/stagger syndrome.
Grazing toxic pastures for only short period can be effective. Sheep do not die suddenly with this condition; there is sufficient opportunity to observe the mob for return of symptoms indicating they have reached their toxin threshold again.
Be prepared to feedlot sheep if there are not alternative safe paddocks. Thousands of sheep enter the feedlots at Portland each year, with just a small percentage of shy feeders overall. Consider preparing a feedlot in small paddocks, laneways or with temporary fencing across corners paddocks with safe waterpoints. Mobs can be boxed, and the period of feedlotting may be just weeks, allowing a detoxification period and assessment of how the season is progressing.
Train weaner sheep to grain
This year due to the excellent spring feed many producers had not fed grain to sheep by the onset of the perennial ryegrass stagger period. Attempting to supplement young untrained sheep reduced the effectiveness of alternative feed sources as a management tool for perennial ryegrass staggers.
Plan alternative weaner paddocks and have a variation in pasture composition across the property
Our best pasture species have periods of toxicity and long-term management would include planning a variation in pasture composition particularly for the weaners, which are most susceptible to perennial ryegrass toxicity.
What the farmers are saying ...
"We have a bit of staggers every autumn. We have never suffered any losses before."
"Could not shear weaners - delayed 3 months then lost 150 due to inclement weather in June"
"Couldn't sell lambs on time"
"Problems with fly strike and can't handle the sheep"
"My health has suffered, bending over too many fly blown sheep"
"Have only been able to crutch 40% of the ewes coming up to lamb"
"Very difficult to remove rams at end of mating period - 3 days instead of usual 1"
"Unable to muster for drenching and crutching"
"Unable to sell cull sheep off shears due to staggers"
"Affected growth rates and still seems to be affecting animal health"
"More important than the deaths was weight loss in wethers at critical time of year for staple strength"
"Foxes are stressing them and they drop and eat them"
"We have a bit of staggers in sheep, every autumn; not cattle. We have never lost any before."
"Unable to drench young cattle on time"
"Cattle caught in troughs & in liquid feed tanks"
"Could not get cattle in to milk or pregnancy test"
"Quite a number of losses in dairy cows, dairy and beef heifers and ewes and prime lambs"
"My husband risked his life in a creek to save a staggering heifer"
"Problem severe and research needed"
The Animal Welfare Science Centre was established by the University of Melbourne, Monash University and the Department of Primary Industries, Victoria. The Centre focuses and coordinates the research and academic resources of the three collaborating organisations, providing the animal industries, animal users, the farming community, Government, the general community and the academic community with an internationally competitive research, teaching and training resource in animal welfare.