my horse escaped and ate A LOT of chicken feed advice please. - Page 3 - The Horse Forum
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post #21 of 28 Old 01-07-2012, 12:28 PM
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Ionophore Toxicosis in Horses

26 July 2010

Ionophore Toxicosis in Horses - A Cautionary Tale
Word from Woodwedge
A recent report of the death of three horses in Alberta5, alleged to have resulted from eating feed medicated or contaminated with the ionophore, Rumensin (crystalline monensin sodium), prompts the writing of this article.
Monensin is one of several biologically active compounds categorized as ionophore antibiotics in use routinely as feed additives to control coccidiosis in poultry and to improve feed efficiency in pasture and feedlot cattle, also of use in the dairy industry6. The concentrated product is rarely to be found on the farm, available only in formulated ruminant and poultry rations at the feed mill. Used properly the compounds are effective but the level of safety is small, and careless use has caused major losses4. Ionophores are specifically prohibited for use in horses at any time because of the unique species sensitivity and toxicity at a very low level intake. There is general agreement that access to ruminant feed, mixing errors, accidental contamination of horse feed in a mill producing poultry, cattle and horse feed are the most common causes for intoxication1,2,3,4.
The heart is the primary target organ of monensin toxicosis. In horses ingesting a sublethal dose of monensin, heart muscle is damaged and replaced by fibrous tissue during the healing process. The result is a structurally weakened heart that can succumb to stress and cause acute collapse of the horse. Myocardial injury and death in horses may occur from a single acute toxic dose of monensin as low as 1 to 2 mg/kg body weight, shown to be several to one hundred times more susceptible than other species.
Monensin toxicosis is suspected when horses show clinical signs of feed refusal, abdominal discomfort, muscle weakness, and heart failure and when a possible exposure to contaminated feed has occurred. Clinically, signs in horses with ionophoretoxicity vary with the type, quantity and concentration of the ionophore, and with the pre-existing health and body condition of the horse. Predisposing factors may include vitaminE/selenium deficiency, T-2 toxin exposure, and any number of drug interactions associated with impaired ionophore metabolism3. Peracute toxicity is manifest as progressive, severehemoconcentration, hypovolemic shock and death within a few hours of ingestion. The acute form is characterized by feed aversion, colic, diarrhoea, profuse sweating, muscle weakness, progressive ataxia, rapid heart rate, difficult breathing and excessive urination, along with signs of central nervous system malfunction. These cases may show signs for 1 to 4 days before collapse and death. Horses surviving sublethal doses of monensin exhibit signs of reduced athletic performance, unthiftiness, and cardiac failure.
Diagnosis of monensin toxicity may be difficult. Laboratory tests must be run soon after the syndrome develops. Many agents are potential causes if sudden death is the only observation, including selenium toxicity, grain overload, ethylene glycol, botulism, vitamin E/selenium deficiency, various plant varieties and neurogenic myopathies3.
A definitive diagnosis of ionophore toxicity is based on detection of the ionophore in the feed or stomach contents of exposed horses4.
Postmortem findings range from no visible lesions to heart muscle pallor and signs of congestive heart failure. If death occurs suddenly, few lesions will be present. If death is delayed, myopathy and congestive heart failure are more apt to be evident3.
Treatment of horses acutely affected may be attempted, usually on a symptomatic basis. Intensive intravenous fluid therapy, activated charcoal or mineral oil orally may be administered4. Although heroic therapy may support the horse during the initial crisis, the prognosis is always guarded because longer term actions of monensin, particularly on the heart, may still cause death. All affected horses are susceptible to cardiac damage, which may be permanent. A critical evaluation of cardiac function and the integrity of any previously intoxicated horse destined to return to some form of athletic endeavour is well advised.
A cautionary word – Biosecurity on the farm or ranch extends to a careful evaluation of all feeds and supplements provided for your horses. Your dealer should be known for quality feeds, properly formulated, stored and delivered. Purchased feed for horses should be kept in a clean, secure, separate area away from other livestock feed and medications or potentially harmful products. If repackaging feed, be sure to use clean bags or containers to avoid accidental contamination5. The integrity of fences/corrals should be assured so there is no possibility of horses gaining access to ruminant or poultry feed.
A healthy CVP (client-veterinarian-patient) relationship always pays dividends, especially in an emergency. You may have little time to develop one in the unfortunate event of ionophore toxicosis involving your horses.
B.W.R. Rothwell, D.V.M 2010.07.22
  1. Radostits, O.M. et al, Veterinary Medicine 9th Edition pp1624-26
  2. Canadian Animal Health Institute, Compendium of Veterinary Products 9th Edition, pp 683
  3. Blakley, Barry: WCVM Student Notes “Ionophores” via email current to 2010.07.19
  4. Lohmann, Katharina: Excerpts from Reed and Bayly Equine Internal Medicine pp 449 (cardiovascular diseases), 527-28 (Disorders of the Musculoskelatal system), 1393-1394 (Toxicologic Problems) via email 2010.07.21
  5. desBarres, Wm., Fwd. copy of email “Important News to Horse Owners” originating from Ms. Anita Doonan, ATRA 2010.07.14
  6. Merck Veterinary Manual 9th Edition pp 2175, 226

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post #22 of 28 Old 01-07-2012, 02:36 PM
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Great article! I know since Rukas chicken feed incident, ingredients are on the bags at UFA with Rumencin warnings. I had the finishing pellets for my pet Rooster that doesn't have that ingredient or it would have been game over for Ruka. At the time i did not even know about Rumencin and a UFA sales person told me what to buy for the rooster since i had no clue. both the dogs and horses would go for the roosters food too. The pellets swell like crazy and it reminds me of volume in beet pulp pellets when you add water. That's why intubation is so very important to grab that feed in their stomach and small intestine and drain it back out through a nose tube, because the impaction and/or colon twist and/or gas can kill the horse.
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post #23 of 28 Old 01-07-2012, 04:30 PM Thread Starter
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The owner of the chickens has said that It is just corn and barley and oats. He has developed laminitis but hasn't colliced thank goodness. When i went to him this morning he could hardly move in a classic lami stance. Vet came out and listened to gut sounds and all is normal he also took temp and that was fine. His stomach is hard but he is passing alot of poo! Vet gave bute as an anti-inflamatory and he will be back to check him tomorrow. He has left me with instructions and what to look out for. He examined the chicken feed bag and said it shouldn't cause him any harm so just close observations for the next few days. I already have a couple of lami ponies so i know what i'm dealing with there. I'm just so glad that he is not in serious danger and i take this as a very harsh lesson learned. Thank you so much for all your concern and kind words I always feel like i can come here with any questions no matter what they are

should i or should i not.........
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post #24 of 28 Old 01-07-2012, 07:24 PM
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Originally Posted by caseymyhorserocks View Post
Not much help but, it is mainly cracked corn right? Although he may get a bout of laminitis, and possibly colic from all that new strange feed, it shouldn't be to terrible, unless it is one of those feeds that has a ton of stuff in it besides the corn,
Casey, that is simply not correct sorry to say. Grain/carb overload & ensuing acidosis can even cause death, & I'd class that as a bit 'terrible'. Corn is one of the worst grains for horses too, for that reason. It can cause serious gut damage & toxicity. Laminitis & colic can be pretty terrible too, even if they don't kill the horse. There is lami & lami & toxicity induced lami can come on very hard & fast.

*So not trying to say all that WILL happen, but not wanting to understate the seriousness of it either. OP I see you're hopefully under control now, but esp if giving bute or such, I'd definitely be giving a probiotic as well, to dampen further negative effects on gut lining & possible further toxicity. Ask your vet - they usually supply that sort of thing.
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post #25 of 28 Old 01-08-2012, 04:19 AM Thread Starter
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I'm just so pleased that the vet doesn't think it's as serious as some of the stories i've been hearing and reading about. My friend told me that she knew of someone in her village who lost 4 horses to the same thing. He has come down with pretty bad lami and is very very sore and stiff on his feet so i know there will be a few weeks of gentle short walks to keep him from ceasing up and thanks for the advice for a probiotic. I've never given one so i'll need to speak to my feed store about which would be best. It's such a relief especially when i have only had him a very short time.

should i or should i not.........
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post #26 of 28 Old 01-08-2012, 04:29 AM
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I'm so glad your boy is relatively ok. Little by little, I'm sure he will continue to improve.

Soooo, while he's not up and at 'em, now is the time to get solid fencing built, so he will not venture out again. Remember, he now knows where the goodies are and will no doubt, try to get at them again. Also, you say you have only had him for a short time. Many horses, when taken into a new home, try to escape. It is often the need to return to buddies at their previous home. Many years ago, I had a mare who constantly jumped a quite high fence and took off to her previous home. The owner finally gave me her old buddy - a gelding. She never tried to leave home again.

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post #27 of 28 Old 01-17-2012, 11:20 AM Thread Starter
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Quick update

He is still very very sore after a week. I had the farrier out to have a look at him as i thought it might also be a touch of foot soreness. He is now shod up as the farrier said he could see no fresh laminitis in his hooves. Although he is better for being shod he still has slight heat in his feet so having to restrict his feed still for the time being and he is still sore but he has perked up alot and is hobbling about better. He hasn't been turned out this week and has just been pottering around in the barn and also i have hand walked him everyday so he has been getting a little bit of exercise i'm hoping another week and he should start to come sound again.

should i or should i not.........
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post #28 of 28 Old 11-26-2013, 11:21 PM
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Hi, I know this is an old thread but I thought this might be useful for others who have a similar problem.
I'm currently studying Veterinary Science and I've just learnt that Monensin (a growth promotant found in chicken feed) is highly toxic to horses. The lethal dose for chickens of this substance is approx. 145mg/KG, where horses only need a dose of 2mg/KG for it to be lethal (i.e. Horses are more than 70x more susceptible to monensin than chickens). Also refrain from feeding horses ruminant feeds, as ruminant feed can contain high amounts of monensin as well (lethal dose is 26mg/KG for cows so can tolerate monensin in their diet)
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