Are Rabon Fly Control Blocks Harmful to Horses?

Rabon fly control blocks are similar to other fly prevention devices marketed for horses. The blocks are designed for horses to lick periodically, and are composed primarily of molasses. Rabon, the larvicidal ingredient in these blocks, prevents the development of numerous fly species and prevents fly eggs from developing in horse manure. In most cases, these blocks are safe for horses.

  1. Dosage

    • Molasses is safe for horses in small quantities but becomes toxic if the horse eats too much. Give horses no more than 1 ounce for every 200 pounds of body weight. Cut the blocks up or only give the blocks to the horses for a brief period each day. Horse owners who move their horses among different pastures each day can limit consumption by putting the fly lick block in one pasture.

    Allergies

    • Before giving a horse any medication, including fly larvicide, consult with a veterinarian. Though it is rare, some horses may have allergic reactions to the molasses or the sugar in the molasses. An equine vet can determine if fly blocks are safe for a particular horse.

    Medical Conditions

    • Horses suffering from laminitis -- frequently referred to as founder -- should not eat molasses fly blocks. This vascular disease causes lameness in extreme cases, and can be exacerbated by the sugars in fly licks. Horses that consume large quantities of fly blocks may become susceptible to laminitis.

    Malnutrition

    • Horses tend to eat large quantities of anything that tastes good. Though many rabon fly blocks are fortified with vitamins such as calcium, they provide insufficient nutrition. A horse that fills up on these substances is unlikely to eat healthier, more substantive food items. For this reason, even fly blocks that are marketed as completely safe or nontoxic should only be fed in small quantities.