Effect of graded levels of defatted green microalgal inclusion into broiler diets on growth performance and digestibility
The objective of this experiment was to determine an optimal inclusion level of a defatted marine green microalgae (Nannochloropsis oceanica), a byproduct of biofuel production, in broiler diets. A total of 180 hatching Ross broiler chicks were divided into 5 groups (n = 6) fed a corn-soybean meal diet containing 0 (Control), 2, 4, 8 or 16% algal biomass (Cellana, Kailua-Kona, HI) for 6 wk. Body weights, feed intake, organ weights, and blood samples were collected at wk 3 and 6; and water intake was measured over the first 3 wk. Over the 6-wk period, ADG, ADFI and G:F were not affected by the algal inclusion up to 8%. However, the 16% inclusion reduced ADG (P < 0.01) and G:F (P < 0.001). Water intake was increased (P < 0.001) by 16 and 39% in chicks fed 8% and 16% microalgae diets, respectively. Relative heart weights were increased by feeding the 16% microalgae diet at both wk 3 (P < 0.05) and wk 6 (P < 0.01). However, relative liver, breast, gizzard, proventriculus and intestinal weights or lengths were not affected by the dietary treatments. The same was also true for plasma uric acid, inorganic phosphorus, and protein concentrations at wk 3 or 6. Dry matter concentrations of total excreta collected from 2 birds per cage over a period of 3 d at wk 6 were reduced (P < 0.05) in the birds consuming the 8 and 16% microalgae diets, compared with the control. However, the excreta total dry matter or nitrogen retention was similar among the 5 experimental diets. In conclusion, dietary inclusion of this new defatted microalgal biomass up to 8% did not exert any negative effects on growth performance or nutrient metabolism except for the elevated water intake. (Supported in part by USDA/DOE Biomass R&D Initiative Grant).
Keywords: green microalgae, broiler nutrition, biofuel