Effect of Encapsulated Fish Oil Supplementation on Growth Performance, Carcass Characteristics, and Blood Immunometabolic Biomarkers in Feedlot Finishing Steers

To investigate the effect of omega-3 fatty acids supplementation through encapsulated fish oil (EFO) on growth performance, carcass characteristics, and blood immunometabolic biomarkers in feedlot cattle, Angus × SimAngus individually housed steers (n = 60; body weight [BW] = 320 ± 29 kg) were used in a randomized complete block design. Prior to initiating the experiment, steers were blocked by BW and randomly selected to receive 1 of 2 dietary treatments consisting of a corn grain-based diet with 0.5% (dry mater [DM] basis) of either EFO or tallow (TLW) as supplemental lipid sources. The experimental diets were administered for a 168-d feeding period, after which steers were harvested. Blood samples were collected from all steers on d -5, 56, 112, and 168 relative to treatment administration for glucose, non-esterified fatty acids (NEFA), insulin, and oxylipins concentration. All data, but the one for oxylipins, were analyzed using the PROC MIXED procedure of SAS, considering the fixed effect of lipid source, time (d), and their interaction as fixed effects and block as the random effect. Principal component analyses for oxylipins were performed using the MetaboAnalyst 6.0 platform to determine treatment differences in the plasma oxylipins. A treatment × d interaction was detected for BW (P = 0.03; Table 1), wherein EFO-supplemented steers were heavier throughout the majority of the experimental period and at study conclusion, relative to the TLW-supplemented cohort. Steers receiving EFO supplementation exhibited a greater average daily gain compared to the steers fed TLW (P = 0.04). No treatment × d interaction nor treatment effects were detected for DM intake and gain to feed ratio (P ≥ 0.11). For the carcass characteristics, EFO-supplemented steers tended to have a heavier hot carcass weight and a greater Longissimus muscle area (P = 0.09; Table 2) than the tallow-supplemented group. No other treatment effect was detected for the remaining carcass characteristics (P ≥ 0.23). A tendency for a treatment × d interaction was observed for plasma insulin and the revised quantitative insulin sensitivity check index (RQUICKI; P = 0.06, Fig. 1). In d 168, steers fed diets with EFO had lower concentrations of plasma insulin and a greater RQUICKI. No treatment × d interaction nor treatment effects were detected (P ≥ 0.15) for plasma concentrations of NEFA and glucose. The plasma oxylipins analysis revealed treatment differences (P < 0.05), with upregulation of anti-inflammatory/pro-resolving oxylipins (5-HEPE, 18-HEPE, 8, 14, 16, 17, and 20-HDoHE, D12-PGJ2, Maresin2) and downregulation of pro-inflammatory oxylipins (5-oxoETE, TXB2, PGE2) in EFO-supplemented steers relative to the TLW-supplemented group. Collectively, these findings suggest that dietary supplementation with omega-3 fatty acids via EFO might improve the growth performance and carcass characteristics of feedlot steers by attenuating systemic inflammation and ameliorating energy metabolism.