Ask the Vet

Prebiotics and Probiotics

(Progressive Farmer image by Chris Clayton)

READER: There has been a lot of talk about probiotics for years, and now I am hearing more about prebiotics in livestock feeds. Can you explain what these things are and what they do?

Dr. McMillan: Probiotics are essentially "good bugs," including bacteria and yeasts, fed to improve digestion and overall health. Prebiotics are non-digestible, soluble fibers that feed and help these bugs grow and multiply.

There are probiotics that can help improve feed efficiency and others that can improve immune function. Some probiotics work in the rumen to improve its function, while others help maintain a healthy intestinal tract. Since probiotics are living organisms, they and the feeds they are in must be properly handled at each stage. Read what the manufacturer says pertaining to proper storage, and follow those recommendations. Dead bugs won't do you much good.

It's a good idea to talk to producers in the area who have used some of these products for a season or two. Much of the research that's been done on these type products comes from the manufacturers, and conditions they've tested those products in may not bear much resemblance to your operation. So, talk to other producers, ask your herd veterinarian for his or her thoughts, and if you decide to try any of these products, keep track of your own data so you'll be able to prove to yourself whether they are effective in your environment.

READER: I read your column that mentioned minerals or feed supplements that help with fly control in cattle. Is there anything like that for horses? -J. Parker

Dr. McMillan: I don't do any equine work anymore, but when I did, fly control was a huge problem. Talking with horse owners and veterinarians, I'm told it still is.

There are many flies that can be a problem around horses, include biting midges, horseflies, deer flies, stable flies, horn flies, face flies and houseflies. Each may require different control measures. Sanitation and moisture control are universal recommendations. Many flies breed in mature and decaying organic material--including feed and hay. Manure must constantly be removed from stalls, barns, paddocks and other high-use areas and properly disposed of. Leftover feed, grain and hay should be cleaned up daily. Remedy any moist areas.

Two insect growth regulators are approved for use with horses. Both interfere with formation of chitin, the primary component of the insect exoskeleton. They prevent molting of fly maggots, and can help with species that use manure in their life cycles.

Diflubenzuron is sold as SimpliFly and Equitrol II. The products are identical and are top-dressed onto grain or mixed into the ration. The dose is 6.8 mg per 100 pounds of body weight. For a 1,000-pound horse, the dosage would be 1 ounce per day. Cyromazine is sold as Solitude IGR. It is an alfalfa-based pellet dosed at 1/2-ounce per day.

These products must be started before fly season starts to be most effective. If neighboring livestock are not on an IGR, these products are likely to be less effective. Not all flies are controlled by IGRs, in which case additional premise or on-animal fly-control products will probably be needed.

Please contact your veterinarian with questions pertaining to the health of your herd. Every operation is unique, and the information in this column does not pertain to all situations. This is not intended as medical advice but is purely for informational purposes.

Write Dr. Ken McMillan at Ask The Vet, 2204 Lakeshore Dr., Suite 415, Birmingham, AL 35209, or email


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