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Fatty acids inhibiting growth of Streptococcus suis in piglets

Denkavit, specialist in feeding young animals and Kemira, manufacturer of organic acids, developed together a new product called Denkacid XL. Test results confirmed positive results in piglets.

Nowadays, one of the main causes of health problems and one of the reasons for using therapeutic antibiotics in rearing piglets is the occurrence of the pathogenic gram-positive bacterium Streptococcus suis.

To tackle this problem more research is needed, e.g. determining the way S. suis is spread within a herd and developing adapted feeding concepts. Different researchers found that S. suis plays an important role in the intestines where it can pass through the intestinal wall (translocation towards mesenteric lymph nodes). This means that S.suis does not only enter the blood through exterior wounds or tonsils finally leading to e.g. meningitis.

A few days after weaning, S. suis can be found indeed at high levels in stomach and intestines and so this offers opportunities to tackle the problems through special new feeding concepts.

The novel product consists of the organic acid mixture Denkacid, based on the short chain fatty acids (SCFA) formic-, acetic-, propionic- and citric acid and calcium salts in combination with extra lipophilic compounds like medium chain fatty acids (MCFA) enriched with lauric acid (C12:0).

With this latter MCFA-mix Kemira found also good effects against another gram-positive bacterium, Clostridium perfringens in broilers.

In vitro model
Together with a Scandinavian laboratory, an in vitro model was developed simulating as much as possible the stomach and small intestines of piglets. In this model several products were tested, among which Denkacid and Denkacid XL.

All test products were initially treated by pepsin-HCL (pH3-4) for 1 hour and by bile acids+pancreatin+NaOH (pH 6.8-7.2) for 3 hours at 37° C prior to introducing them in the simulation vessels.

As growth medium for the simulation model, distal ileal digesta was taken from five piglets and pooled. A buffer solution (pH 6,5) was added, the growth medium was maintained anaerobic and the test products were added. Finally, fresh ileal digesta of two piglets was spiked with live E. coli and S. suis bacteria and added into the simulation vessels.

Each test product was applied at four dosages and with five replicates. After an incubation for ten hours the vessels were sampled for analysis. Tables 1 and 2 below show the results of the bacteria analysis.

Table 1. Effect of Denkacid on number of E. coli bacteria.

Table 1 shows that both Denkacid and Denkacid XL have a strong dose-dependent growth inhibition on E. coli. Moreover, (data not shown) E. coli as percentage of the total bacteria flora was reduced significantly (p<0,001) from approximately 9% in the negative control group to less than 1% at the highest dosages.

The inhibitory effect on E. coli was slightly stronger with Denkacid than with Denkacid XL, which can be explained by the diluting effect on the SCFA by the added lipophilic compounds to the latter.

Table 2. Effect of Denkacid on number of S suis bacteria.

Table 2 shows that both acid products have an effect on Streptococcus suis at higher dosages. However, Denkacid XL showed an utmost significant (p<0,0001) reduction of Streptococcus suis at lower dosages.

With this in vitro simulation study of the piglets’ gastro-intestinal tract it is shown, probably for the first time, that problems with Streptococcus suis can be tackled through a judicious use of feed additives. A product based on organic acids and their salts in combination with specific fatty acids enriched in C12:0 can significantly inhibit the growth of Streptococcus suis.

The fact that both pathogenic bacteria E. coli and S. suis could be suppressed offers great opportunities to raise piglets with less health problems and to reduce the amount of antibiotics used in pig production.

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