Californian worms biomass growth and its zinc accumulation under different concentrations of the metal in the nutrient medium

The ability of worms to accumulate biotic metals in their body creates the preconditions for obtaining a protein-mineral supplement containing metals in the organic compounds. Experimental studies on the worms reproduction, their mass increase and zinc organic forms accumulation in their body, depending on the content of this metal in the nutrient medium were carried out. Zinc content in the nutrient medium for worms was regulated by adding various doses of this metal salt (ZnSO4 • 7H2O). Worms were grown for 110 days on a nutrient medium with a different content of zinc. It has been established that adding Zinc at a dose of 160 mg/kg of nutrient medium provides increase in the worms number and weight by 1.5–1.9 and 1.55–1.96 times, respectively, as compared to the worms grown on a nutrient medium without zinc addition. The negative impact of zinc at a dose of 640 mg/kg of nutrient medium on the worms mass increase was established. Vermiculture mass was 12.9% lower than the control under high dose of the metal. Additional application of zinc at doses of 40 mg/kg, 80, 160, 320 and 640 mg/kg in growing worms on a nutrient medium provided increase in the content of this element in vermiculture dry mass, respectively, by 20.4%, 31.7, 50.0% or by 2.7 and 3.0 times.