Growth and carcass fatty acid composition of beef steers fed soybean oil for increasing duration before slaughter.

Duration of soybean oil (SBO) supplementation needed to enhance carcass conjugated linoleic acid (CLA) and trans-vaccenic (TVA) content was examined using 96 beef steers (293.6±3.9kg) fed a 78% corn-based diet supplemented with SBO for 0, 77, 137, or 189days before slaughter. Duration of SBO supplementation had no effect (P⩾0.15) on animal performance or carcass traits, nor (P⩾0.15), total, total saturated, or total polyunsaturated fatty acids of Longissimus dorsi (LD). Concentrations of CLA in LD were not affected (P⩾0.18) by SBO supplementation. Concentrations of monounsaturated fatty acids (MUFA) decreased linearly (P=0.03) in LD, whereas TVA increased (P=0.04) in adipose tissue and tended (P=0.07) to increase in LD with increasing duration of SBO supplementation. Supplementing SBO to a concentrate-based diet may enhance TVA without impacting CLA, while reducing the MUFA content of lean beef.