In this study, the diet selection of piglets regarding a commercial piglet feed with addition of a charge of Herba Thymi, containing 1,73 % (v/w) essential oil, or Herba Origani, containing 1,80 % (v/w) essential oil, or a combination of both compared with the same commercial feed without an herbal additive was tested. The herbs were added in concentrations of 0,02 % and 0,002 % (v/w) each (orientation on the content of essential oil) to the feed. The test method was based on the Latin square of Williams. Compared with the standard feed all test feeds were rejected, 5 test feeds significantly (p < 0,05). The test feed with 0,1 % Herba Thymi was not rejected significantly (p = 0,13).
In addition, the essential oil of each herb was tested against 6 haemolytic E. coli isolates (O 147 K91; O 147 K89; O 147 K85 ab; O 138 K81; O 149 K91; O 139 K81) in a disk diffusion susceptibility test.
Minimum inhibition and minimum bactericidal concentration were determined by microdilution broth method. Thyme essential oil, starting with a concentration of 0,6 % (v/v), and Origanum essential oil, starting with a concentration of 0,3 % (v/v), had both an bactericidal effect on all E. coli isolates in vitro.
In this study, the antimicrobial potential of Herba Thymi and Herba Origani in vitro against the tested E. coli isolates was confirmed. The tested charges of Thymus vulgaris L. and Origanum vulgare L. showed no positive effect on the acceptance of feed in the used concentrations as feed additive.
Thymus vulgaris L. / Origanum vulgare L. / feed additive / acceptance of feed / piglets / E. coli / antimicrobial activity