Abstract
To investigate the impact of encapsulated fish oil (EFO) supplementation on growth performance, carcass characteristics, blood immunometabolic biomarkers, and adipose tissue inflammation in feedlot cattle, Angus × SimAngus crossbreed steers (n = 60; body weight [BW] = 320 ± 29 kg) were used in a randomized complete block design. Steers were blocked by BW and origin and randomly selected to receive 1 of 2 dietary treatments consisting of a finishing diet with 0.5% (DM basis) of either EFO or tallow (TLW) as supplemental lipid sources. To assess adipose tissue inflammation and plasma oxylipins, a subset of 6 steers per treatment were randomly selected for collection of adipose tissue (d -5, d 100, and postmortem) and blood samples (d -5, 56, 112, and 168). The luminescence intensity of the CD172a was used as a proxy of adipose tissue inflammation. For plasma metabolite analysis, blood samples were collected from all steers on d 56, 112, and 168. Mixed models (SAS PROC GLIMMIX and MIXED procedures) were used for statistical analyses. A treatment × d interaction was detected for BW (P = 0.03), where the EFO-supplemented steers were heavier throughout the experimental period and at study conclusion than the TLW-supplemented cohort. Steers supplemented with EFO exhibited a greater average daily gain compared to the TLW-supplemented group (P = 0.04). For the carcass characteristics, EFO-supplemented steers tended to have a heavier hot carcass weight and a greater Longissimus muscle area (P = 0.09) than the TLW-supplemented group. A tendency for treatment × d interaction was observed for plasma insulin and the RQUICKI (P = 0.06). In d 168, steers fed diets with EFO had lower concentrations of plasma insulin and a greater RQUICKI. The plasma oxylipins analysis revealed treatment × d interactions (P ≤ 0.05), wherein EFO supplementation induced a sustained upregulation of omega-3-derived anti-inflammatory/pro-resolving oxylipins throughout the experiment, whereas omega-6-derived pro-inflammatory oxylipins exhibited a transient downregulation, evident on d 56. No treatment × d interaction nor treatment effects were observed on the CD172a intensity in subcutaneous and visceral adipose tissue (P ≥ 0.23). These findings demonstrated that supplementing feedlot steers with EFO modulated the plasma oxylipin profile toward a pro-resolving state and improved growth performance, carcass characteristics, and energy metabolism.