Microalgae meal (MA; Schizochytrium limacinum CCAP 4087/2) was fed to finishing heifers (n = 285; 453 ± 24 kg initial BW) to assess impact on growth performance, carcass traits, and fatty acid composition in plasma. Heifers were stratified by weight, randomly assigned to pens of 8 animals each, and fed diets based on steam-flaked corn and corn gluten feed for 89 d. Treatments consisted of 0, 50, 100, or 150 g/animal daily of MA (Alltech, Inc., Nicholasville, KY) that was included in the feed additive premix and subsequently mixed in the total ration. Approximately 6 h before feeding, blood was collected via jugular venipuncture from 3 animals/pen on d 21 and 82 for analysis of plasma concentrations of eicosapentanoic, docosapentaenoic, and docosahexaenoic acids (EPA, DPA, and DHA, respectively), which are long chain omega-3 fatty acids that are most active within the body. Feeding MA did not affect ADG (P = 0.58), but decreased DMI (P = 0.16) and increased G:F, HCW, yield grade, and percent of USDA Choice carcasses in a dose dependent manner (linear, P < 0.08). Plasma concentrations of EPA (3.5, 23.6, 86.3, 153.5 ± 4.64, respectively), DPA (13.4, 15.4, 22.4, 30.8 ± 1.04, respectively), and DHA increased in proportion to the amount of MA fed (linear, P < 0.01). Data were analyzed as a randomized complete block design using the PROC MIXED procedure of SAS 9.4 (SAS Inst. Inc., Cary, NC) with pen as the experimental unit and animal as the observational unit. Microalgae meal has potential for improving growth performance and assimilation of omega-3 fatty acids into beef tissues. Table 1. Performance, hot carcass weight, and plasma DHA concentrations

Item	0	50	100	150	SEM
DMI, kg/d	9.81	9.62	9.45	9.54	0.163
Gain:Feed1	0.0844	0.0889	0.0873	0.0929	0.0031
HCW, kg1	702.0	687.6	715.0	723.1	12.2
DHA, μg/g plasma2	5.3	26.5	38.8	46.8	1.42

¹Linear effect (P < 0.07). ²Linear effect (P < 0.01).