Winter Active Max P Fescue linked to horse poisonings

PASTURE agronomist Ross Watson, Scone, says horse owners throughout Australia should not graze their horses on any pasture containing the Max P® Mediterranean Fescues, (also widely known as winter active fescues) following three horse deaths at Scone and Canowindra, and many cases of horse illness on five properties in Scone, Canowindra, Albury, Cootamundra and Kangarilla in South Australia.

Mr Watson, a consultant to horse studs throughout the Hunter Region, said that at present, Flecha Max P® was the variety associated with the majority of cases, possibly because its seed accounted for the majority of seed sales, and therefore sowings, over recent years. However, he said all Mediterranean /winter active fescues with Max P might also be implicated, which included “VNS” (Variety Non Specific) fescue seed lines and downgraded Max P fescue seed lines.
Mr Watson said that horse owners were advised to no longer sow Max P Mediterranean fescue or any pasture blend containing these specific fescue lines until the problem was clearly understood.
“Property owners who might have these fescue pastures primarily sown for cattle or sheep should not place their stock horses or children’s ponies on such pastures,” he said.
Mr Watson said there had been a total of 59 horses on five properties, grazing pastures that contained the Mediterranean fescues and 47 of these horses had been affected. Based on this, there was a high risk of horses becoming seriously ill or dying on these pastures.
“This is the first case of this problem ever being reported in the world,” he said.
“This problem is something the pasture and the horse industry did not need.”
The new Fescue Poisoning Syndrome, known as “Equine Fescue Oedema” (EFO), is very different to the widely recognised Fescue Toxicosis that occured in America, when horses graze high endophyte or “wild type” fescue pastures.
As soon as this problem was first reported in October 2007, a team of pasture and veterinary experts from Australia and New Zealand were put together by PGG Wrightsons , the marketers of Max P fescues in Australia, to investigate this problem. Extensive pasture sampling from all affected sites were collected and carefully prepared in Australia late last year, for detailed analysis by AgResearch NZ in January 2008. These complex analyses have taken some time and are continuing, but because this is a new and complex problem it is not going to be an easy task to pin point the compound and when, where and why this has occurred, Mr Watson said.
"Initially no one was sure whether it was in fact the fescue, certain veterinary drugs, contaminated feed supplements, a toxin associated with other grasses in the pastures or some rare fungi or bacteria which had attacked the fescue and had produced the toxin," he said.
But over the last month and with the recent Canowindra case, Mr Watson said the overwhelming field and veterinary evidence accumulated certainly pointed to the Max P Mediterranean fescue containing some unknown toxin. On this basis, he said this warranted a public awareness campaign.
While the answer to the problem might take many months to fully investigate, in the mean time, Mr Watson said horse owners everywhere needed to be aware.
"Until we know for sure, we think it is appropriate that people are aware of the problem, and hopefully we will have a definite answer on what has caused this problem in the near future," he said.
As a result, Mr Watson said that horse owners would have to reconsider their pasture options.
"As far as fescues, only Certified, Nil or Zero Endophyte Mediterranean fescue seed lines such as Flecha (Non Max P version) and Resolute (Non Max P version), Prosper and Fradyo winter active fescues can be considered safe for horses," he said.
"Interestingly, the Summer Active or Continental Max P fescue lines such as Quantum Max P, Advance Max P and Jessup Max P have been used for many years on horse studs in Australia with absolutely no problems.
"Max P fescues are pasture lines inoculated with a specially selected endophyte fungi. These fungi naturally live inside the grass plant in a symbiotic relationship. They produce chemical compounds which give the host pasture plant much better resistance to insects, heat stress and drought. Novel endophytes have been used successfully in pastures in NZ, Australia and the USA for more than 15 years in perennial ryegrass and fescue pasture lines. They have made a major difference to the productivity and persistence of ryegrass and fescue pastures. It will be a major loss to the pasture industry throughout the world if MaxP technology is jeopardised," Mr Watson said.
Dr Bourke, Principal Veterinary Scientist with NSW DPI, Orange, has been assisting the working group on Equine Fescue Oedema.
He said that some of the consistent clinical signs were that the horses becqme lethargic, depressed, loose their appetite and are inclined to lie down.
"Most develop mild to moderate swelling of the head and neck as a result of a build up of fluid below the skin which is called an oedema, and at the same time they develop oedematous thickening of the wall of the right dorsal colon," he said.
"This is visible on scan images of the abdomen. They go on to develop oedema of the chest and belly (ventral oedema), including accumulation of fluid within the abdominal cavity. Whereas the head and neck oedema quickly resolves, the ventral oedema can persist for several weeks. Protracted weight loss and associated anoestrous are risks for affected lactating mares. Secondary inflammatory changes such as peritonitis are possible in some animals. The prolapse of the rectum has also been observed."
Dr Bourke said that vets dealing with Equine Fescue Oedema needed to be aware that the outstanding and consistent finding is a drop in total blood plasma proteins with values as low as 27 but typically 35 to 45 g/L (normal range 52-79). This is due to an albumin decline, with albumin values recorded of about 8 to 12 g/L (normal range 19 -32). The PCV is elevated, eg 56 to 70 (normal 36-48). If the albumin drop is too severe the horse will die before plasma administration can restore it. During the recovery phase plasma proteins may not return to normal for several weeks. In some affected horses these biochemical and blood changes can develop quite suddenly and return to normal quite quickly once they are moved off the pasture.

Extensive pasture sampling and chemical testing to date has not conclusively identified the problem, but the overwhelming available evidence is pointing to an issue related to the chemical compounds produced by the Max P endophyte in winter active fescues.
This is a very lethal toxin with only small amount of the toxin needed to kill or make an adult horse very sick.
"We feel all horse owners need to be aware of this problem, so any further horse deaths or animal ill health can be avoided," Dr Bourke said.
"Cattle and sheep grazing these same pastures have shown no obvious effects to date. Many thousands of cattle and sheep have grazed these sort of pastures over the last five years and there has been no reported problems associated with this type of fescue. Cattle and sheep owners should report any similar symptoms or stock losses on fescue pastures."
The Max P fescues have been widely and successfully established throughout temperate areas of Australia, especially in NSW, Victoria and South Australia since 2005.
"The first reported case was in Scone in September 2007 and the most recent case was at Canowindra in March 2008. However, the vet and stud manager at a horse stud in Southern NSW noted horses affected by EFO, when grazing pastures which did contain fescue in 2006, but did not know what it was and did not report the case. So at the moment no one can be sure if and when this fescue is “safe” to horses. We do know that in many cases horses have grazed these paddocks for periods before the poisonings occurred, with no known effects, but suddenly we have had this problem. We are not sure now when the high risk period is," Dr Bourke said.
"The many affected horses in spring 2007 were brood mares in pasture paddocks with foals at foot, but geldings, stallions and young yearling horses have all been affected. Clinical cases first appear about three to seven days after horses start grazing a toxic pasture but with mixed pastures it may take some weeks, depending on pasture composition and horse selectivity. If they are immediately removed from the toxic pasture, then most affected animals will return to normal within another three to seven days, but some may require supportive therapy in the form of plasma administration, and some may die despite this treatment. Some affected horses may take up to 28 days to recover."
Mr Watson said the contacts below would appreciate hearing from any other horse owners who have experienced Equine Fescue Oedema problem or who are grazing Max P Mediterranean fescues with horses with no reported problems.
Horse owners who have sown pastures containing Mediterranean Max P fescue, should contact their local seed reseller, agronomic adviser or PGG Wrightsons in Melbourne on their Hotline 1800 619 910 to discuss their pasture options.