Increasing Dietary High-Linoleate Safflower Oil Affects Duodenal Flow of Esterified Linoleate in Wethers

We hypothesize that lambs fed a highconcentrate diet with high-linoleate safflower oil will have increased duodenal flow of 18:2c9,c12 (18:2, linoleic acid) due primarily to flow of esterified 18:2. Four crossbred wethers (BW = 44.3 ± 15.7 kg) fitted with ruminal and duodenal cannulae were used in a 4 × 4 Latin square experiment to determine duodenal fatty acid flow when fed an 80% concentrate diet with increasing levels of highlinoleate (77%) safflower oil (oil; 0, 3, 6, or 9% of DM). Wethers were fed diets, at 2% of BW, that were formulated to be isonitrogenous and included bromegrass hay, cracked corn, corn gluten meal, urea, limestone, plus oil. Duodenal digesta, collected to represent every 2 h in a theoretical 24h period, was extracted with chloroform, methanol, and water (1:2:0.8) in tubes containing tritridecanoate as internal standard. Half of each lipid extract was used for methyl ester preparation using 1.09 N HCl in methanol to catalyze methyl esterification of total (free plus esterified) fatty acids. The other half of each lipid extract was transesterified with 0.2 N KOH in methanol to catalyze methyl esterification of only esterified fatty acids. Fatty acid intake increased (linear, P < 0.004) with increased dietary oil. Duodenal flow of both total (linear, P = 0.007) and esterified (linear, P = 0.002) fatty acids increased from 0 to 9% dietary oil. Total to esterified fatty acid ratio of duodenal digesta increased (linear, P = 0.08) with increased dietary oil, indicating greater ruminal lipolysis with increased dietary oil. Ratio of total 18:2 to esterified 18:2 in duodenal digesta increased (linear, P = 0.06) from 0 to 9% dietary oil. However, within each treatment, duodenal flow of total 18:2 was not different (P ≥ 0.32) than that of esterified 18:2. Duodenal flow of 18:1t-11, a major biohydrogenation intermediate, increased (linear, P = 0.04) as dietary oil increased suggesting that biohydrogenation was less complete as dietary oil increased. We conclude that the increase in duodenal flow of 18:2 that occurred from increased dietary oil could be accounted for by increased flow of esterified 18:2.