THE USE OF DIRECT-FED MICROBIALS BY
THE HORSE INDUSTRY
Larry Roth, Ph.D.
Conklin Co. Inc.
A healthy and beautiful horse is the pride of every horse owner. Feeding selected
cultures of lactic acid-producing bacteria and yeast boosts horse health and
performance, according to many owners. Understanding the benefits of direct-fed
microbial cultures can help you decide when to use these products during your
horse’s
life cycle.
In 1908, the Russian biologist Eli Metchnikoff credited the long lives of certain
Bulgarian
and Russian citizens to the consumption of large amounts of fermented milk products
(4). The key organism in these foods was later identified as Lactobacillus acidophilus,
a
lactic acid-producing bacteria (10). The lactic acid-producing bacteria are so
named for
their ability to produce lactate. However, lactate production is only one of many
benefits
derived from this collection of bacteria. The lactic acid-producing bacteria most
frequently featured in direct-fed microbial products include Lactobacillus acidophilus
and
Enterococcus faecium.
For many centuries, people have observed that their animals were healthier when
fed
feedstuffs resulting from yeast fermentation. Yeast are fungi, or one-cell organisms
that
reproduce by budding, or producing daughter cells. The yeast species most utilized
by
the direct-fed microbial industry are Saccharomyces cerevisiae and Aspergillus
oryzae.
Based on the work of Metchnikoff and others, the idea was developed to directly
feed
live, lactic acid-producing bacteria and yeast to animals for improving their
health and
performance. The observed benefits may result from: 1) competition for attachment
sites in the digestive tract, 2) competition for essential nutrients, 3) production
of
antimicrobial substances, 4) increasing the growth of beneficial bacteria and
5)
stimulating the immune system (8).
Competition For Attachment Sites In The Digestive Tract
Some disease-causing bacteria reduce an animal’s ability to absorb nutrients
by
disrupting the small intestine (8). Lactic acid-producing bacteria attach to the
lining of
the small intestine and produce a substance to prevent disease-causing organisms
from
binding to the intestinal wall (7). The attachment of the beneficial bacteria
may increase
the absorptive surface area of the small intestine and enhance enzyme activity
for
greater nutrient absorption by the animal (8, 11).
Competition for Essential Nutrients
Lactic acid-producing and disease-causing bacteria require certain nutrients for
growth.
The beneficial bacteria could utilize vitamins, amino acids or other nutrients
that might
otherwise support the growth of harmful bacteria (5).
Production Of Antimicrobial Substances
The ability of direct-fed microbial cultures to inhibit disease-causing organisms
is of
considerable interest. Lactic acid lowers the intestinal pH to create an environment
unsuitable for harmful organisms (8). Lactic acid-producing bacteria secrete hydrogen
peroxide, resulting in conditions unfavorable for oxygen-requiring microorganisms
(2).
Bacteria produce bacteriocins that restrict the growth of other microorganisms,
often
genetically related species (8). The lactic acid-producing bacteria have demonstrated
the ability to inhibit E. coli, Salmonella typhirium, Staphylococcus aureus and
Clostridium perfringens (5). The reduction of scour-causing organisms is especially
important in new-born and young animals.
Increasing The Growth Of Beneficial Bacteria
Enhancing the growth of beneficial bacteria boosts the performance of healthy
animals.
The B-vitamins, enzymes and other factors secreted by lactic acid-producing bacteria
and yeast stimulate starch- and fiber-digesting bacteria (3, 5). The ability of
yeast to
enhance fiber digestion could allow dietary changes (12). The ability of yeast
to
increase feed intake has been recognized for centuries.
Stimulating The Immune System
Recent advances in animal health indicate the importance of proper immune function.
Research indicates that lactic acid-producing bacteria heighten immune function
at the
digestive tract and whole-system levels (6). Experiments with bacteria-free extracts
from lactic acid-producing cultures demonstrate improved macrophage activity against
E. coli (9) and Salmonella typhirium (1). The role of direct-fed microbial cultures
in
stimulating the immune system warrants further research.
The Use Of Direct-fed Microbial Products With Foals
Although foals are born with bacteria-free digestive tracts, the tract is quickly
populated
by disease-causing and health-promoting bacteria. The question becomes, “Which
type
of bacteria will dominate?” Providing direct-fed microbial cultures shortly
after birth can
favor the beneficial bacteria. Studies suggest that lactic acid-producing bacteria
inhibit
scour-causing microorganisms, and can aid in the absorption of nutrients. Microbial
gels and pastes are available for oral delivery to foals, or dry cultures can
be mixed with
milk replacers.
The Use Of Direct-fed Microbial Products With Growing And Mature Horses
Diet changes and other challenges at weaning can alter a foal’s nutrient
intake and
health status. Controlling harmful bacteria in the digestive tract during variable
feed
intake is very important. The microbial gel and paste products can be placed directly
in
the foal’s mouth, and the owner can confidently know that an animal with
low or no feed
consumption received the intended microbial dose. Dry products can be mixed with
the
feed for daily maintenance.
Yeast cultures aid in stabilizing the microbial balance in the digestive tract,
which may
reduce the problems resulting from grain over-consumption and colic. In addition,
yeast
stimulates fiber-digesting bacteria to increase the energy a horse derives from
forages.
Consequently, the ration composition could shift in favor of forages over grains,
increasing the safety of the horse’s diet. Always consult your veterinarian
or nutritionist
before making dietary changes.
Breeding, foaling, showing and heavy training can alter feed intake and increase
a
horse’s susceptibility to disease-causing organisms. Restoring nutrient intake,
stabilizing the balance of digestive tract bacteria and proper immune function
become
critical during these challenging periods. Many horse owners suggest that direct-fed
microbial cultures can play a major role during these critical periods. In addition,
improving the nutritional status of the horse enhances the hair coat and durability
of the
hooves. The oral and feed products used for younger horses work equally well with
mature horses, although the amount of lactic acid-producing bacteria and yeast
should
be increased.
Direct-fed Microbial Products And Storage
Direct-fed microbial products are available that feature only lactic acid-bacteria
or yeast,
and others include bacteria and yeast combinations. Microbial gels and pastes
are
placed between the lower teeth and cheek of the horse. Certain dry powders are
dispersible in milk replacers and liquid feeds. Other dry products are readily
mixed in
the feed. However, always be sure to purchase reputable products handled properly
by
the manufacturer and seller. The direct-fed microbial products should be stored
in cool,
dry locations to maintain their microbial viability.
Feedstuffs resulting from microbial fermentation have benefited animals and their
owners for many centuries. Continuing research projects document the need to include
direct-fed microbial products in horse management programs. Many horse owners
have
experienced the benefits of directly feeding live bacteria and yeast to their
animals.
_________
Larry Roth, Ph.D. is a research scientist with Conklin Co. Inc.; 551 Valley Park
Dr.;
Shakopee, MN 55379. Questions concerning direct-fed microbials and requests for
the
research references supporting the article should be directed to Dr. Roth.
References Cited
(1) Hatcher, G.E. and R.S. Lambrecht. 1993. Augmentation of macrophage phagocytic
activity by cell-free extracts of selected lactic acid-producing bacteria. J.
Dairy Sci.
76:2485.
(2) Klaenhammer, T.R. 1982. Microbiological considerations in selection and
preparation of Lactobacillus strains for use as dietary adjuncts. J. Dairy Sci.
65:1339.
(3) Martin, S.A. and D.J. Nisbet. 1992. Effect of direct-fed microbials on rumen
microbial fermentation. J. Dairy Sci. 75:1736.
(4) Metchnikoff, E. 1908. Prolongation of Life. G.P. Putnam’s Sons. New York.
(5) Montes, A.J. and D.G. Pugh. 1993. The use of probiotics in food-animal practice.
Vet. Med. March 1993:282.
(6) Perdigon, G. et al. 1988. Systemic augmentation of the immune response in
mice
by feeding fermented milks with Lactobacillus casei and Lactobacillus acidophilus.
Immunology 63:17.
(7) Savage, D.C. 1985. Effects on Host Animals of Bacteria Adhering to Epithelial
Surfaces. In: Bacterial Adhesion, D.C. Savage and M. Fletcher (eds.); Plenum,
NY;
pp. 437-463.
(8) Savage, D.C. 1991. Gastrointestinal Microbial Ecology; Possible Modes of Action
of
Direct-fed Microbials in Animal Production. In: Direct-fed Microbials in Animal
Production; National Feed Ingredients Assoc.; Des Moines, IA; pp. 11-81.
(9) Schiffrin, E.J. et al. 1995. Immunomodulation of human blood cells following
the
ingestion of lactic acid bacteria. J. Dairy Sci. 78:491.
(10) Shahani, K.M. and A.D. Ayebo. 1980. Role of dietary lactobacilli in gastrointestinal
microecology. Am. J. Clin. Nutr. 33: 2448.
b
(12) Williams, P.E.V. et al. 1991. Effects of the inclusion of yeast culture
(Saccharomyces cerevisiae plus growth medium) in the diets of dairy cows on milk
yield and forage degradation and fermentation patterns in the rumen of sheep and
steers. J. Anim. Sci. 69:3016.
