Effect of supplementing feedlot steers with a DHA-rich microalgae meal on performance, insulin sensitivity, and meat quality

Abstract Text: Heterotrophic production of algal biomass provides a consistent, high quality source of docosahexaenoic acid (DHA; C22:6 n-3) in triglyceride oils that could be used as a ration supplement for feedlot steers to improve healthfulness of beef. Sixty Angus x Simmental steers (438 ± 6.4 kg) were allotted to 2 treatments (30 steers each, 6 pens, 5 steers per pen) to determine the effect of a supplemental DHA-rich microalgae meal (Schizochytrium limacinum CCAP 4087/2; 63.6 % fat; 17.9% DHA; Alltech Inc.) on performance, insulin sensitivity and meat quality. Steers were fed basal diets containing 45% corn, 30% distillers dried grains with solubles (DDGS), 20% corn silage, and 5% supplement at 0800 daily. Basal diets were formulated to contain 16.1% CP, 1.32 Mcal/kg NEg, and 0.12 mg/kg Se. A top-dress was delivered daily to provide 3 mg/hd selenium (Se; sodium selenite) to control steers and 3 mg/hd Se as organic Se (Sel-Plex®, Alltech Inc.) + 100 g DHA-rich microalgae meal to algae steers. A glucose tolerance test (GTT) was performed 10 d prior to slaughter to determine glucose clearance and insulin production. Steers were slaughtered when a target BW of 621 kg was achieved. Fatty acid oxidation potential was determined by measuring thiobarbituric acid reactive substances (TBARS) on LD samples collected 24 h after slaughter and aged for 48 h or 21 d. Data were analyzed using the MIXED procedures of SAS. Weight and BW gain did not differ during the study (P ≥ 0.13), but algae steers were in the feedlot 7 more d compared to control steers (111 vs. 104 d; P = 0.04). Overall DMI was decreased (P = 0.002) and gain:feed during the second half of the study was increased (P = 0.04) in algae compared to control steers. Steers fed algae secreted less insulin (P = 0.01) and took longer to clear glucose (P = 0.01) during a 2 h GTT. Carcass traits did not differ between treatments (P ≥ 0.23). Concentration of TBARS did not differ in LD aged for 48 h (P = 0.91), but when aged for 21 d, steers fed algae meal tended to produce LD with greater TBARS concentration compared to control steers (P= 0.08). In conclusion, DHA-rich microalgae meal decreases DM intake of steers and increases measures of fatty acid oxidation in meat aged for 21 d.

Keywords: Beef, Algae, DHA, TBARS