Glucosinolate Tolerance Limit in Hybrid Striped Bass

Glucosinolates (GLS) are pungent compounds that function in predator deterrence or in nonspecific immune responses in plants. GLS are antinutrients when consumed by animals, because break-down products reduce feed palatability and interfere with normal thyroid functioning, resulting in reduced growth. The tolerance limits of GLS have been determined in some cultured fish species (1.4-11.6 µmol/g of feed) and vary considerably. In this study, GLS tolerance was determined for hybrid striped bass (HSB) using feeds containing GLS from 0, 1, 1.5, 2.0, 2.5, 3.0, 4.0 and 5.0 µmol/g of feed. The feeds were made by including incremental levels of cold-pressed carinata seedmeal (61.2 µmol/g of dry meal) into isonitrogenous (42 % protein) and isocaloric (4.16-4.26 Kcal/g) feeds. There were no differences observed in growth, FCR, fish condition or organosomatic indices. Visceral fat generally increased with increasing GLS. There were no differences in thyroxine (T4), triiodothyronine (T3) or the activities of deiodinase (D) enzymes 1, 2 and 3 in the kidney, liver and brain, respectively. Nonspecific health indices were also not different among treatments. Based on this data, the HSB tolerance limit for dietary GLS should be above 5.0 µmol/g.