Bovine Serum Fatty Acid Analysis

Trial 2. Individual cow body weight (BW) was recorded once at the beginning of the trial and at the end of each period. Blood samples were collected from each cow every 12 h on day 19 of each period via jugular venipuncture using Serum Z/9-mL Luer Monovette collection tubes (Sarstedt Inc., Newton, NC, USA). Blood samples were allowed to clot at room temperature for about 1 h and then stored for 24 h at 4 °C. All blood samples were centrifuged at 2000× g at 4 °C for 20 min. Serum was then collected into separate tubes and stored at −20 °C until analysis. Duplicate 1 mL serum aliquots from all steers were lyophilized (HarvestRight, North Salt Lake, UT, USA) and then transmethylated according to Tipton et al. [19 (link)]. An internal standard, methyl tricosanoic (C23:0), was incorporated into each sample during methylation. Each sample of fatty acid methyl esters was analyzed using a Shimadzu GC-2014 gas chromatograph equipped with a Shimadzu AOC-20s automatic sampler. Separations were completed using a 60 m high resolution gas chromatography column (Agilent Technologies, Inc., Santa Clara, CA, USA). Samples were run at a split ratio of 10:1. Fatty acids were identified by comparing the retention times of known standards.