Essential oils mix reduced lice attachment by 68% in trial

A functional feed additive based on essential oils of oregano, thyme, and citrus reduced sea lice attachment levels in Atlantic salmon by almost 70% in controlled conditions.

The phytogenic additive, included in feed at three levels of 400, 800, and 1,200 grams per tonne, was developed by speciality ingredients company DSM-Firmenich and tested in vivo at the seawater research facility operated by Stirling University’s Institute of Aquaculture at Machrihanish on the Kintyre peninsula in western Scotland.

Salmon post-smolts (186g) were acclimated for seven days in seawater tanks and then fed one of the trial diets or a control diet for 45 days, before being challenged with sea lice (Lepeophtheirus salmonis). The trial continued for a further 53 days, when sea lice were counted, in addition to zootechnical performance and welfare scoring.

Results showed a near-70% decrease in the total number of lice in the two highest inclusion doses (800 and 1,200 g/t), and there was a concomitant increase in the percentage of fish without any lice in those treatments.

Feed intake was unaffected not negatively affected by the inclusion of the phytogenic mix, which DSM-Firmenich calls Digesterom, and final body weight, feed conversion ratio, and specific growth rate were similar across all four diets, researcher Ester Santigosal, of DSM-Firmenich Animal Heath and Nutrition Switzerland, said in a presentation at the Aquaculture Europe conference in Valencia yesterday.

After the presentation, she told Fish Farming Expert that the trial had been carried out in controlled conditions, and that the next step would be large-scale commercial testing.

As part of that goal, DSM-Firmenich is making the product available to fish farmers in northern Europe who wish to try it out. Because Digestarom is a natural phytogenic, it doesn’t require new licensing.