LAUSR

Algae production is increasing to supply the growing demand for Omega-3 fatty acids for aquaculture, human food and pet food; co-products from the algae industry could be a suitable feed ingredient for cattle feeding. A safety study was conducted to evaluate feeding algal biomass to cattle. Crossbreed 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 a finishing diet (62.5 to 70% corn and 15% distillers grains) for a minimum of 97 d. At harvest, organs were weighed and sampled. Blood was collected every 30 d. Performance data were analyzed as a RCBD with treatment, gender, and treatment by gender interactions as fixed effects, BW block as a random effect and individual animal as the experimental unit. Orthogonal contrasts were used to test for linear, quadratic and cubic responses due to CARS inclusion. Increasing CARS in the diet quadratically increased DMI and ADG (P ≤ 0.01). A linear increase was observed for G:F, NEm,and NEg as CARS increased in the diet (P < 0.01). All organ weights measured were within expected ranges for cattle, with 6 out of 27 having differences in weight due to treatment (P ≤ 0.05). Histopathology analysis of organs revealed no differences due to treatment (P ≥ 0.24). Out of 21 blood chemistry measures, 8 were affected by treatment (P ≤ 0.02). Nearly all blood chemistry parameters were within expected ranges for cattle. No adverse effects of feeding CARS were observed in hematology, blood chemistry, or histopathology analyses. The feedstuff CARS demonstrated to be a safe and efficacious feed ingredient for cattle diets and maximized HCW, ADG, and DMI when fed at 2.5 or 5% of the diet.