A new type of defatted green microalgae exerts dose-dependent nutritional, metabolic, and environmental impacts in broiler chicks

The potential of defatted microalgae from biofuel production in animal feeding remains unclear. The objective of this experiment was to determine the metabolic and environmental impacts of a defatted green microalgal biomass (DGA, Nannochloropsis oceanica, Cellana, Kailua-Kona, HI) in broiler chick diets. Day-old chicks (total = 180) were fed the control diet containing zero, 2, 4, 8, or 16% of DGA for 6 wk to determine the optimal level of DGA inclusion. Compared with chicks fed the control diet, only those fed the 16% DGA diet had lower (P < 0.05) ADG and feed use efficiency. The DGA feeding produced dose-dependent (linear) increases in starter period water intake (P < 0.0001, R2 = 0.76) and in wk 6 relative weights of heart (P < 0.0001, R2 = 0.45), liver (P = 0.09, R2 = 0.19), and intestinal tract (P = 0.02, R2 = 0.19), retentions of soluble inorganic phosphorus (P = 0.001, R2 = 0.39) and DNA retention (P = 0.001, R2 = 0.46), and ileal DNA content (P < 0.0001, R2 = 0.50). Meanwhile, the DGA feeding led to weak linear decreases (P < 0.05, R2 = 0.14 to 0.27) in wk 6 tibia weight and length and excretion of soluble inorganic phosphorus. In contrast, the DGA feeding did not affect relative weights of breast, proventriculus, or gizzard, tibial bone strength, or plasma DNA concentrations. In conclusion, this new type of DGA biomass may be supplemented into diets for broilers at 8% without adverse effects if the salt content is decreased.