What are ionophores and their common uses?
Ionophores are a class of antibiotics commonly added to bovine feed supplements to promote feed efficiency and growth. These products are also used to reduce and control coccidia in cattle. Brand names you might recognize include Rumensin, which contains monensin, and Bovatec, which contains lasalocid. While useful in ruminants, they can be deadly for cattle, sheep, goats, and horses when fed at too high a level.
Why are ionophores particularly dangerous for horses?
Horses should never be given access to anything containing Rumensin or Bovatec because consumption of these products can cause severe diseases, ranging from sudden death to chronic heart damage that can progress to heart failure over months or years. Toxic levels of ionophores cause direct damage to muscle cells of the heart, skeletal muscle, and smooth muscle lining internal organs. This can lead to colic, muscle weakness, abnormal gait, neurologic disease, and heart disease or heart failure. As little as 50 milligrams can result in death within 48 hours of exposure in normal-sized adult horses.
Dr. Emily Gosda
Crazy Mountain Veterinary
How did Megan's horses get exposed to ionophores?
According to Megan, a gate was left open in their barn, allowing the horses to access where the feed was stored. They managed to pull the feed through some panels and consumed it. The feed in question was bull challenger pellets containing Rumensin, and it was the only bag they had left.
How much feed did the horses consume?
Megan estimated that there was about a quarter of a bag left, approximately 25 to 30 pounds, which was consumed by the six horses.
What was the immediate response to the exposure?
Megan and her team immediately loaded all the horses and brought them directly to the vet. Five of the six horses were treated as one was not seen near the feed. The treatment included multiple tubing sessions with mineral oil and charcoal to prevent absorption of the Rumensin, and the horses were put on fluids for the first 12 hours, with IV catheters set up for fluid administration. Additionally, they were given medications like vitamin E, selenium, and banamine, and monitored closely for changes in heart rate and rhythm.
What were the outcomes for the horses?
Fortunately, the five horses that received treatment did not show any clinical signs and have been doing well. Unfortunately, the sixth horse, which did not receive treatment as it was not thought to be exposed, passed away within 48 hours of exposure.
What advice does Megan have for other horse owners?
Megan highly encourages horse owners who also have cattle to look into alternatives to Rumensin, as there are many safe options on the market now. She emphasizes that despite taking precautions, accidents can happen, and using safer additives is a better option.
What precautions should be taken when using ionophores?
Dr. Emily Gosda advises that Rumensin and Bovatec are great feed additives for cattle when used in the right amounts. However, it's crucial to store these products far away from horses to prevent any risk of serious disease or sudden collapse from cardiac issues. Ensure that the feed containing ionophores is kept in separate locations inaccessible to horses and always be aware of the ingredients in the feed provided to cattle, sheep, or goats.
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