Another consideration when using phytogenic feed
additives is possible interactions with other feed additives. Many of the feeding trials investigating the effi-
cacy of phytogenic feed additives included other growth
promoters (e.g., antibiotics, organic acids, and probiotics), as well as combinations with them, without showing antagonistic interaction among these feed additives.
On the other hand, studies on interactions of phytogenic
feed additives with enzyme preparations (e.g., phytase,
enzymes degrading nonstarch polysaccharides, etc.) are
very limited. For example, Sarica et al. (2005) reported
a lack of or negative interactions of garlic and thyme
with nonstarch polysaccharide-degrading enzymes in
broilers. Phytogenic feed additives containing components with astringent properties, however, were reported to interact negatively with proteinaceous feed
additives through partial denaturation (Anadon et
al., 2005).