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Discussion on Selenium toxicity
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Member:
maggienm
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Posted on Wednesday, Apr 22, 2009 - 9:51 am:
Hi Dr. O
I live in a very selenium deficient area. So, it is well known to supplement your horse.
In the desire to feed well some people feed multiple concentrates, all of which have various amounts of minerals in content.
During a meeting(pony club) last night we were discussing feeding guidelines and such.
Selenium came up as it always does. The question was asked, "what are signs of selenium overdose/toxicity?"
I did do a search but couldn't find anything.
Also, in regards to selenium have you heard that a lack of selenium could contribute to tying up?
thank you
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Member:
3chip
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Posted on Wednesday, Apr 22, 2009 - 12:13 pm:
The maximal tolerable level of selenium in horses is estimated at 2 mg/kg of diet (NRC, 1980), and the LD50 for orally administered selenium is considered to be approximately 3.3 mg of selenium (as sodium selenite)/kg of body weight (Miller and Williams, 1940). Copper pretreatment can increase the LD50 markedly (Stowe, 1980).
Acute selenium toxicity--blind staggers--is characterized by apparent blindness, head pressing, perspiration, abdominal pain, colic, diarrhea, increased heart and respiration rates, and lethargy (Rosenfeld and Beath, 1964).
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Member:
maggienm
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Posted on Wednesday, Apr 22, 2009 - 5:42 pm:
Ha, wouldn't you know it, I found the link that talks about my very question.
Any idea on how long it takes for selenium to build up and become a problem.
I suppose the answer would depend on how much is being ingested.
Once it was discovered that too much is being fed, how quickly does the selenium leave the system?
thank you.
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Moderator:
DrO
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Posted on Thursday, Apr 23, 2009 - 7:50 am:
Lori,
The article Horse Care » Equine Nutrition, Horse Feeds, Feeding » Selenium in Horses discusses chronic and acute toxicity. How quick you develop symptoms and what symptoms are seen will depend on the dosage rate. Once dietary levels are lowered the selenium will begin to decrease but how long to normal has not been studied in horses that I am aware of and will depend on the level and type of poisoning.
In pigs there is a large study of a wide spread feed associated chronic poisoning where the rate of decrease was pegged at a half life of 12 days. Every 12 days the Selenium level halved after a subacute poisoning.
DrO
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Member:
ekaufman
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Posted on Thursday, Apr 23, 2009 - 1:40 pm:
Just want to chime in (maybe an obvious point) that the effects in a horse can well outlast the poisoning. Had a horse come in for training once who had had selenium poisoning. His hooves actually sloughed mostly off, and it was a year before he had feet worth walking on.
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Member:
maggienm
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Posted on Thursday, Apr 23, 2009 - 1:55 pm:
ok, thank you.
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Member:
cgby1
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Posted on Thursday, Apr 23, 2009 - 9:49 pm:
I just heard today that the polo horses that died had been accidently poisoned by a selenium overdose by a pharmacy that made a special supplement for that stable.
Cynthia
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Member:
vickiann
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Posted on Friday, Apr 24, 2009 - 4:17 pm:
Cynthia, I just heard this too.
Here is a good reason to know math and decimals as we work.
Ten times the appropriate amount of selenium was reportedly used by accident.
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