Selenium – poison or miracle?

Selenium (native), alongside a pen for scale. from the mineral collection of Brigham Young University Department of Geology, inwards Provo, Utah. © Andrew Silver

Is selenium a poison, or a miracle benefit? The answer depends on your purpose of it – equally good much or equally good fiddling is a problem.

Selenium (Se) was deemed an essential food solely inwards 1957, simply was discovered inwards 1817. Before that, explorer Marco Polo referred inwards his journals to “a poisonous flora … which if eaten past times (horses) has the upshot of causing the hoofs of the beast to driblet off.” What Marco Polo constitute inwards the 13th century is instantly persuasion to last a flora known equally a selenium accumulator, which stores toxic amounts of selenium.

Such plants are non persuasion to be inwards New Zealand, simply are prevalent inwards the arrive at areas of the north-central United States, as well as one, Morinda reticulata, is reported inwards around areas of Queensland.

Scientists at the University of Wyoming discovered that most plants – fifty-fifty those on soils containing selenium – contained 10 parts per meg or less of selenium, whereas a selenium marking of 14,990 ppm was constitute inwards a sample of Astragalus racemosus, which is a selenium accumulator.

In New Zealand, toxicity is caused past times overdosing, or past times using to a greater extent than than i selenised production at a time. Symptoms of selenium toxicity include abnormal movement, night watery diarrhoea, high temperature, weak as well as rapid pulse, laboured respiration, bloating as well as abdominal pain, pale as well as bluish mucous membranes, as well as dilated pupils. Most animals alongside selenium toxicity are constitute dead, as well as at that spot is no antidote for those constitute alive.

Selenium deficiency tin atomic number 82 to White Muscle Disease, which causes degeneration of the skeletal muscles, strong gait, as well as other problems.

Veterinarians spoken to virtually selenium toxicity as well as deficiency were reluctant to give precise figures of the recommended levels of supplementation, because of surface area as well as farm variations inwards the levels. Some studies study that a 3rd of New Zealand soils are selenium deficient.

A North Canterbury veterinarian, who did non want to last named, said the marking of supplementation needed depended on blood as well as liver levels. “It is non something that y'all tin extrapolate to all farms – it is an private farm as well as an private beast problem, thus y'all necessitate to make upward one's take away heed what the selenium condition is earlier y'all get supplementing, as well as the condition of the plants, equally the selenium is coming upward from the soil. You outset necessitate to make upward one's take away heed that at that spot is a deficiency, thus teach alongside a supplementation programme based on that.”

View of a see musculus from a Equus caballus that died due to severe selenium deficiency. The lighter colored tissues are see musculus cells that died prematurely.

He pointed to the latest NZ Veterinary Association update, which has reported beast deaths from selenium toxicity, caused past times double dosing. The NZVA reported several pockets of deaths inwards younger as well as older animals.

Labnet Invermay’s study for May 2002 ascertained that depression selenium levels were diagnosed equally causing ill-thrift inwards iv groups of yearling cattle, as well as 6 herds were constitute through blood testing to guide maintain selenium deficiency.

The North Canterbrury veterinary says 3 or iv blood or liver samples tin last used to make upward one's take away heed the marking or the herd or flock. “In dairy cattle we’ll teach to, say, a 400-cow herd as well as guide maintain 3 samples, as well as that volition give us a expert persuasion virtually the condition of that herd.”

Delivery methods of selenium depend on the administration of the farm: “For animals that are handled daily, such equally dairy cattle, selenium tin last added to the drench thus that they teach a daily dose. The marking volition depend on the deficiency.” In i case, a 1ml daily dose of a 0.5 per cent solution was given on i North Island farm.

Beef herds tin last supplemented alongside deadening loose bullets inwards the rumen, which terminal from ix months to a year.

Injections tin also last given. “Often selenium is combined alongside a Vitamin B12 injection. Selenised prils on the Blue Planet give a 12-month marking of selenium, “but you’ve got to last careful non to purpose whatsoever other selenised production without consulting a vet,” he said.

Farmers should also last aware that around drenches incorporate selenium, thus attention must last taken when using a selenised vitamin B12 injection inwards conjunction alongside drenching.

Horses as well as selenium are a hot topic afterward the recent representative of a North Island racehorse trainer who was constitute to guide maintain several horses inwards his attention alongside selenium toxicity. The horses guide maintain difficulty inwards moving, as well as inwards come upward cases their hooves appear to last coming off.

A Christchurch Equus caballus veterinarian, who also did non want to last named, said that selenium was dispensed solely to clients of the clinic, as well as inwards cases where the vets had seen the holding as well as were aware of the province of affairs of the horses. “There are basic guidelines for feeding selenium, simply everyone’s province of affairs is different,” he says.

“Racehorses who are inwards stables unremarkably teach especially balanced feeds alongside selenium inwards it. If the trainer is feeding solely chaff as well as grain thus they’d in all likelihood last supplementing alongside selenium, simply if they’re feeding a consummate feed they would non be. It also depends on how much run the Equus caballus is doing as well as what province of affairs they’re in.”

In cases where horses are turned out on grass, alongside no extra feed “some variety of supplementation is advisable, for certain inwards the Canterbury area, equally it is renowned to last selenium deficient. But, again, it’s an surface area thing. And around people may last on a farm as well as they know they’re putting selenium on the pasture, thus they don’t necessarily necessitate to last supplementing the horses.”

He advised horses owners to verbalize to their vet for recommendations. “There are thus many varied ways inwards which people feed their horses, that y'all can’t give a full general guideline. The province of affairs would last dissimilar for a lifestyle block compared to a high-country farm, where they’re putting a lot of selenium on their pasture, whereas on a lifestyle block perhaps they don’t. These dissimilar properties guide maintain all got dissimilar aspects that necessitate to last looked at.”

 

Dose rates:

• Dose equally per veterinary advice as well as the guidelines on the product’s label.

 

First published on Horsetalk.co.nz inwards June, 2002.

 

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