Horse News & Views - June 2004

Ministry of Agriculture, Food and Rural Affairs

Ontario Association of Equine Practitioners

• Trimethoprim sulfa (TMS) is a commonly used broad spectrum antibiotic combining two ingredients (trimethoprim with one of two different sulfonamides). They are synergistic and are readily absorbed orally. TMS is often used in the treatment of respiratory tract infections and, when administered orally, should be given 30 minutes prior to feeding. Horse handlers, however, should be aware of some drug interactions. The use of antacids concurrently, e.g., for ulcer treatment, may decrease the bioavailability of the sulfonamide. Sulfonamides may displace, and therefore enhance, the effects of some drugs such as phenylbutazone (Bute). Your veterinarian will be able to provide you with a monogram with the details of these interactions. (Plumb D. Veterinary Drug Handbook, 4th ed. St. Paul: Iowa State Press, 2002)
  
• The Illinois Department of Agriculture is now requiring that all livestock, including horses, being shipped into the state for production or exhibition must have a permit issued by the state. The Illinois Department of Agriculture will issue the permits no more than 72 hours before the animals are transported. To avoid lengthy delays, check with state officials for the current health regulations before traveling to the USA.
  
• An often-asked question is "When is it safe to turn out a horse that has been recently gelded (castrated) with mares?" The general consensus is that his fertility will be depleted by 7 days and probably gone by 21 days. However, his libido or willingness to mount a mare will depend on the season, age when castrated and previous sexual experience.

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