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Larry Roth, Ph.D.                                   

The first months of a young foal’s life are perhaps the most challenging. The young foal is

susceptible to respiratory and digestive system diseases that can have life-long effects.

    Numerous horse breeders are using direct-fed microbial products, featuring lactic acid producing

bacteria, yeast and enzymes, to favorably influence the digestive tract of new-born

foals. Establishing and maintaining the proper balance of bacteria in the intestinal tract should

improve the survivability and growth of young foals.

    The digestive tract of a new-born foal is completely free of bacteria. However, the tract quickly

becomes inoculated with both health-promoting and disease-causing bacteria. The health of

the foal is determined, in part, by which bacteria dominate the digestive tract. Diarrhea

resulting from E. coli or Salmonella can rapidly dehydrate a new-born foal. A foal weakened

by diarrhea frequently has a diminished immune system and becomes susceptible to

respiratory diseases. Conversely, a young foal suffering from respiratory diseases will nurse

less and become a prime candidate for digestive problems.

Milk quality changes associated with the foal heat can disrupt the balance of digestive tract bacteria.

The sooner the beneficial bacteria establish dominance, the greater the opportunity for a healthy foal.

    Research studies1 indicate that lactic acid-producing bacteria, such as Lactobacillus

acidophilus and Enterococcus (formerly Streptococcus) faecium, attach to the lining of the

small intestine and improve nutrient absorption by the host animal. Increasing the nutrient

absorption by young foals will enhance their growth, feed efficiency and health. In addition,

intestinal binding by the beneficial bacteria reduces the opportunities for harmful bacteria to

colonize the small intestine.

    Microbiologists have learned that the lactic acid-producing bacteria produce several factors to

hinder the growth of disease-causing bacteria. The production of lactic acid aids in

establishing a digestive pH unfavorable to the growth of E. coli and Salmonella. The E. coli

and Salmonella require oxygen for full metabolism. Yeast metabolism in the digestive tract will

lower oxygen availability and consequently reduce the activity of pathogenic bacteria. The

production of hydrogen peroxide by the lactic acid-producing bacteria can disrupt viral

membranes. Reducing viral activity in the digestive tract could enable the immune system

resources to focus on the respiratory tract rather than the digestive tract. The beneficial

bacteria also produce protein compounds called bacteriocins to limit the growth of undesirable


The lactic acid-producing bacteria and yeast produce B-vitamins, enzymes and other

substances to promote the growth of beneficial bacteria. Numerous research studies support

the ability of yeast to stimulate fiber-digesting bacteria. Maximizing fiber digestion is especially

important as young foals start consuming forages and other fiber-containing feeds.

The balance between beneficial and harmful bacteria in the digestive tract of young foals can

potentially influence their performance as adults. Placing direct-fed microbial products

formulated as gels in the mouth of young foals soon after birth aids in establishing a population

of health-promoting bacteria. The feeding of yogurt to foals supplies a very small amount of

beneficial bacteria. An average cup of yogurt contains only 50 million colony-forming units

(CFU) of bacteria, in contrast to an equine microbial product containing 1.25 billion (CFU) per

cc of gel. In this comparison, a 2 cc dose of the microbial product would supply the same

health-promoting bacteria as 50 cups of yogurt.

 The direct-fed microbial products are also available as dry powders for daily mixing with the

feed or drinking water to maintain a healthy balance of intestinal bacteria. Mixing the direct-fed

microbials with the drinking water has the advantage that sick foals will be more likely to drink

than to eat. A daily supply of the beneficial bacteria could promote nutrient absorption in the

small intestine and foster fiber fermentation in the large intestine. Forage and concentrate

intake prior to weaning prepares the foal for the rigors of separation from the mare.

A healthy digestive tract is necessary for proper growth and health in young foals. Many horse

breeders have reported that direct-fed microbial products aid in improving the survivability and

performance of their foals.


Larry Roth, Ph.D., is a research scientist with Conklin Co. Inc.; 551 Valley Park Drive;

Shakopee, MN 55379.

Dr. Roth can be contacted for more info on direct-fed microbial research studies.