FITOBACT® : Protección de la flora digestiva


G. Huyghebaert Ministry of the Flemish CommunityCLO-DVV

B-9820 Merelbeke, Belgium g.huyghebaert@clo.fgov.be

5. Herbs & etheric oils

Many plants have beneficial multifunctional aspects which are derived from their specific bio-active components. Biologically active constituents of plants are mostly econdary metabolites,such as terpenoids (mono-and sesquiterpenes, steroids,…), phenolics (tannins), glycosides and alkaloids (present as alcohols, aldehydes, ketones, esters, ethers, lactones, …). There is a lot of variation in composition due to: biological factors (kind of plant, growing location, harvest conditions), manufacturing factors (extraction/distillation, stabilisation) and storage conditions (light, temperature, oxygen tension and time). The challenge is to identify and quantify the multitude of actions and claims improving feed utilisation, animal physiology and health status. Because of possible ‘synergy’ between the constituents, it remains rather unclear what component of the etheric oil acts as stimulator of the endogenous digestive enzymes, antioxidant, antimicrobial agent (incl. specificity), immunomodulator,…

There is a lot of experimental data showing the in-vitro anti-microbial activity with respective MIC-values and specificities; e.g. Garlic is more inhibitory against E. coli, Salmonella sp., Campylobacter sp.,Staphylococcus aureus and Clostridium perfringens than against lactic acid bacteria. Even though most suppliers of feed grade products based on plant extracts are careful not to use this evidence due to the legislative constraints, their effects cannot be ignored. According to Adams (1999) the antimicrobial activity is rather weak for ginger and pepper, medium for cumin (p-cymene), coriander (linalol), oregano (carvacrol), rosemary (cineol), sage (cineol) and thyme (thymol) and strong for clove (eugenol), mustard (allylisothiocyanate), cinnamon (cinnamaldehyde) and garlic (allicin).

The main components in oregano-oil are carvacrol (60-80%) and thymol (2%) (patented as Ropadiar);carvacrol inhibits the metabolism of the microbial cell wall (Smink, 2000). The anti-microbial activity in garlic is mainly mediated through the activity of allicin (as an alliinase-mediated breakdown molecule of alliin), which inhibits the growth of many bacteria, yeasts and fungi (Amagase et al., 2001). The broadspectrum mechanism of these components (as a thiosulphonate) is based on the inactivation of the SH containing microbial enzymes. Cinnamon also has an anti-microbial an antifungal activity through the activity of cinnamaldehyde. The products of Enteroguard are combining garlic and cinnamon substances, whereby Enteroguard-starter has a high allicin/cinnamaldehyde-ratio while Enteroguard-finisher has a high cinnamaldehyde/allicin-ratio between According to Sarma and Sapcota (2000), a polyherbal compound Liv-52 is very efficient in improving the zootechnical performance of broilers. The main botanical additives are encompassed by the EU-legislation Directive 91/248, in group C.

All natural products may be included in animal feeds without any limitations. Regarding the botanical additives there is consequently no well-defined legislation. In fact, herbal products should undergo the same procedure for definite standards, efficacy and safety testing as other additives before being allowed to enter the feed chain. The ultimate quality criterion of herbs, however, is the presence of chemical constituents that confer a health benefit. For most herbs, a range of compounds has been ascribed with biological activity with often-unresolved synergistic effects between individual compounds.