Dr Ioannis Mavromichalis
Organic acids are without doubt the most commonly used replacements for
antimicrobial growth promoters. As organic acids are quite expensive, questions
regarding their correct use never cease to come up in conversations. Here I
describe some common recent issues.
Organic acids are without doubt the most commonly used replacements for
antimicrobial growth promoters. Although there is currently no perfect
replacement for 'antibiotics', organic acids have proven they can offer the best
alternative.
That is, at least, in terms of performance, if not in terms
of cost! As organic acids are quite expensive, questions regarding their correct
use never cease to come up in conversations. Below are the most common issues I
have faced in the last couple years.
* Which acid is the
best?
Unfortunately, there is no simple answer to this question.
Different acids are effective against different microorganisms. Moreover, acids
affect the gastrointestinal pH according to their own strength, expressed as
pKa. Today, there are several criteria that help a nutritionist or veterinarian
select the right acid for the right job.
* One acid or
more?
Research and experience has shown that a blend of acids always
works best in cases where a plethora of microorganisms are targeted under
diverse farm conditions. Among the most popular blends, those of formic, lactic,
and propionic are widely used. Nevertheless, a properly selected strong acid can
definitely be more effective than an unspecific blend of weak
acids!
* How much should I use?
Original research on
acids was done with up to 2% acids in complete feed. At such levels, organic
acids prevented scours and enhanced growth performance. Current practice,
however, calls for inclusion levels starting from 0.1%, with more 'aggressive'
levels being 0.5%. This is mainly due to cost considerations. Exact dosage,
again, depends on pathogenic load and overall farm conditions. The more likely
the pigs to scour post-weaning, the higher the dose should
be.
* Will pigs go off feed if I use too much?
Most
likely not as pigs enjoy a tangy taste, especially that coming from citric acid!
Organic acids should be used up to lowering the pH of complete feed down to
4-4.5. Below this level pigs might start refusing feed, but this depends on the
overall feed composition.
* Are inorganic acids
effective?
Yes and no! Phosphoric acid is effective in lowering
gastrointestinal pH, but it is largely ineffective against direct suppression of
pathogens. Hydrochloric acid, which is the acid secreted by the stomach, is
quite effective, but its practical applications are not well established. More
research is needed on this one!
* Should essential oils be combined
with acids?
Yes! When these two are combined together, it appears
that their action becomes synergistic. Essential oils are less expensive than
acids - at least at practical inclusion levels - but their true potential is
rarely expressed when used alone. There, the right combination of essential oils
is equally important as all products are not created
equal!
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