direct-fed microbials (DFM)
or direct-fed microbials (DFM), are live microbial feed supplements which
beneficially affect the host animal by improving its microbial balance (Fuller,
1989). Although the first use of the term probiotic was by Parker in 1974,
Metchnikoff initially proposed the concept in 1907 (Cole and Fuller, 1984).
Since then, a multitude of microbial cocktails have been sold to livestock
these early versions often did not improve livestock performance. This was
mainly due to either ignorance of the fragile nature of bacterial viability
outside of the host, or desire to make a quick buck. This earned probiotics a
poor reputation that they are still struggling to overcome today. Probiotic
effectiveness depends on several factors:
Viability Many of the modes of action listed below depend on live
microorganisms. Viability is reduced by exposure to sunlight and/or heat. Proper
storage is required to insure microbial viability up to or beyond the stated
expiration date. Refrigeration or storage in a cool place away from sunlight is
Selection of proven effective strains Bacteria can be good, bad, and
indifferent. Careful research is required to identify which is which. Several
species have already been demonstrated to be effective, including
Lactobacillus sp., Streptococcus faecium, yeast (Saccharomyces
cerevisiae), and certain species of fungus (Aspergillus sp.).
Concentration Most probiotics on the market contain from 107 to
108 viable microorganisms/gram. Generally speaking, the higher the
concentration, the more effective the product.
microorganisms must survive several hazards, including low pH in the stomach and
digestive enzymes in the small intestine. A large number of initial
microorganisms must be fed to insure enough remain viable by the time they reach
their target. The effectiveness of probiotic microorganisms is often attributed
to the enzymes they secrete. However, this is just one mode of action. Others
Decreasing pH by production of volatile fatty acids (VFA)
Competition for nutrients
Production of substances toxic to pathogens
Production of antibiotic-like substances
Competition for adhesion sites
the modes of action described above involve competition. For this reason, the
probiotic mechanism is often called competitive exclusion . Pathogens would be
able to dominate the digestive microflora under normal, healthy conditions if
they were better competitors. In many cases, opportunistic pathogens, as they
are called, wait in small numbers for disaster to strike. Usually, the only time
they can gain the upper hand is when the animal is stressed (Tannock, 1983).
are usually available in two concentrations. The lower concentration is meant to
be fed to healthy animals on a daily basis (MSE Microbial Concentrate or
granulated ), and is often mixed with feed. Probiotics with greater numbers of
viable microorganisms are designed to be fed preventatively before major
stresses or to treat animals that are already sick (MSE Micronial Paste or
Drench). This latter concentration is usually available either as a paste or
way to protect livestock is to use prevention. This means the daily and
preventive use of probiotics and quarantining sick animals. There are other,
more severe prevention methods such as foot baths, showers and clothing change,
but they may be a little extreme for exotic livestock production.
of what causes stress, this includes biological events such as birth and
weaning; production activities such as shearing, transport, and showing; and
weather, especially extremes and alternations in temperature. Probiotics can
protect against stress if the right strains and numbers of viable microorganisms
Cole, C. B. and R. Fuller.
1984. A note on the effect of host specific feremented milk on the coliform
population of the neonatal rat gut. J. Appl. Bact. 56:495-498.
R. 1989: Probiotics in man and animals. J Appl. Bacteriol. 66,
R. B. 1974. Probiotics, the other half of the antibiotics story. Anim. Nutr.
G. W. 1983. Effect of dietary and environmental stress on the gastrointestinal
microbiota. Pages 517-539 in Human intestinal microflora in health and
disease. D. J. Hertges, ed. Academic Press, New York,
MSE probiotics are available online at
Please contact ruminant nutritionist Lark
Burnham if you have any questions (firstname.lastname@example.org).