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Influence of algae meal as a replacement of corn in feedlot lamb diets on nutrient digestibility
Recent advances in technology support use of heterotrophic microalgae for the production of oils for bioenergy. Oil is extracted and the resultant coproduct includes a combination of de-oiled microalgae and soyhulls, resulting in an algae meal with a unique profile of protein, fiber, and fat. To determine the effects of algae meal (ALG) on diet and nutrient digestibility and N retention, ten whiteface cross wethers (33.71 ± 0.55 kg) were used in a replicated 5 x 5 Latin square. There were 5 periods, each with 10 days of diet adaptation followed by 5 days of total fecal and urine collection. Sheep (n = 2 sheep·diet-1·period-1) received one of 5 diets: a corn-based control (CON), 15% algae meal (15ALG), 30% algae meal (30ALG), 45% algae meal (45ALG), and 60% algae meal (60ALG). Algae meal replaced corn on a DM basis. Data were analyzed using Proc Mixed of SAS and LSMEANS and pooled SEM are reported. Dry matter intake was lesser (P = 0.01) for CON (1.04 kg/d) than ALG-fed lambs (1.15, 1.29, 1.19, and 1.25 ± 0.271 kg/d for 15ALG, 30ALG, 45ALG, and 60ALG, respectively). Dry matter digestibility linearly (P < 0.001) decreased as ALG inclusion increased (75.1, 73.3, 69.8, 68.0, and 67.5 ± 0.70% for CON, 15ALG, 30ALG, 45ALG, and 60ALG, respectively). Digestibility of NDF and ADF were lesser (P ≤ 0.01) for CON than ALG-fed sheep. However, there was a cubic effect (P < 0.03) of ALG inclusion on NDF and ADF digestibility, with lesser digestion in CON, intermediate and similar digestion across 15ALG, 30ALG, and 45ALG, and greater digestion in 60ALG. Ether extract digestibility was lesser (P = 0.002) for CON than ALG, with a linear (P = 0.002) increase as ALG inclusion increased (83.5, 87.0, 87.9, 87.9, and 89.5 ± 1.20% for CON, 15ALG, 30ALG, 45ALG, and 60ALG, respectively). There was a cubic (P = 0.03) effect for N digestibility with 45ALG and 60ALG being lesser and CON being greater than all other treatments. Nitrogen balance did not differ (P = 0.22) between CON and ALG. Results of this study suggest ALG is readily consumed by lambs at up to 60% of diet DM and in relation to commonly available concentrate feeds offers a comparable digestibility. Algae meal could potentially replace portions of corn or soyhulls, serving as a viable component of feedlot diets.
Keywords: Algae, digestibility, sheep