Evaluation of the safety of an algal biomass as an ingredient for finishing cattle

Coproducts of n-3 fatty acid production from algae are a potential feed resource for cattle. A study was conducted evaluating feeding algal biomass to cattle. Crossbred cattle (20 steers and 20 heifers, 255 kg initial BW, SD = 14) were individually fed 4 inclusions of condensed algal residue solubles (CARS; 0, 2.5, 5, 7.5% of diet DM) displacing dry-rolled corn in the finishing diet for a minimum of 97 d. Increasing CARS inclusion in the diet quadratically increased DMI and ADG (P ≤ 0.01) and linearly increased G:F (P < 0.01), NE_m, and NE_g. Out of 27 organs measured, 6 had differences due to treatment in absolute weight and weight as a percentage of BW. Weight of the liver, pancreas, jejunum, and heart linearly increased (P ≤ 0.05) and weight of the thyroid and gall bladder quadratically increased (P ≤ 0.04) as CARS inclusion in the diet increased. However, organ weights were all within expected ranges, and histopathology analysis of organs revealed no differences due to treatment (P ≥ 0.24). Hemoglobin and hematocrit concentrations quadratically decreased (P = 0.05) and red blood cell distribution width linearly increased (P = 0.02) as CARS inclusion increased; no other differences were observed for hematology measures (P ≥ 0.11). Out of 21 blood chemistry measures, 8 were affected by treatment (P ≤ 0.02). Inclusion of up to 7.5% of diet DM as CARS had no adverse effect on cattle and improved performance when fed up to 5.0% of the diet DM.