as flavours stimulate the digestive system and by this improve nutrient digestibility.
Furthermore, essential oils act against oxidative processes, and growth of bacteria
and moulds, both in the gastrointestinal tract (GIT) and in the feed (Table 2).
Bitterns and hot stuffs are of less importance as most phytobiotics contain
only small amounts of these ingredients. Bitterns are reported for thyme and sage
(carnesol) and hot stuffs for chilli (capsaicin) (Heyland et al., 2006). It is well
documented that poultry is in favour of bitter taste, whereas, high contents of hot
stuffs result in feed rejection.
Natural colorants (xanthophylls) are included in most phytobiotics. The
dominant xanthophylls are lutein, zeaxanthin, β-carotene and lycopene. In chilli
capsanthin and capsorubin are responsible for the red colour. Xanthophylls are