PSI-16 Trans-10 biohydrogenation intermediates are negatively associated with the monounsaturated-to-saturated fatty acids ratio in backfat of calf-fed Holstein steers.

Abstract The cis monounsaturated fatty acids to saturated fatty acids ratio (cMUFA:SFA) in beef fat is known to positively impact both the healthfulness and palatability of the meat. Previous research has suggested that the cMUFA:SFA ratio in beef fat increases as marbling score increases. Conversely, cell culture studies using bovine adipocytes have shown that trans (t)10,cis (c)12 conjugated linoleic acid (CLA) can inhibit the biosynthesis of cMUFA, particularly oleic acid, in adipose tissue, leading to a reduced cMUFA:SFA ratio in beef fat. The objective of this study was to investigate the effects of carcass yield grade (YG) and quality grade (QG) on the cMUFA:SFA ratio in the backfat of calf-fed Holstein steers. Additionally, we investigated relationships between major biohydrogenation intermediates, including t10-18:1, t11-18:1, t10,c12-CLA, c9,t11-CLA, and cMUFA:SFA in backfat. A total of 180 Holstein steers (initial body weight of 135 ± 15 kg) were fed a similar steam-flaked corn-based diet and slaughtered after 407 days of feeding at a commercial beef packing plant. Hot weights, camera-assisted yield grades and marbling scores were recorded, and all carcasses were sampled for back fat (~50 g) over the 12th-13th rib. Backfat subsamples (40 mg) were freeze-dried and direct-methylated using sodium methoxide, followed by GC analysis of the resulting fatty acid methyl esters. The correlation of camera yield grade and marbling scores with cMUFA:SFA in back fat were analyzed using the R lm() function in addition to the correlations between cMUFA:SFA and concentrations of c9,t11-CLA, t10,c12-CLA, t10-18:1, and t11-18:1. Correlation analyses showed no significant relationship (r = 0.061, P=0.421) between marbling score and cMUFA:SFA in backfat or between YG and cMUFA:SFA in back fat (r = -0.1, P=0.169). We also found a significant inverse association between cMUFA:SFA and the concentrations of t10-18:1 (r = -0.4, P< 0.001) and t10,c12-CLA (r = -0.51, P< 0.001) in the backfat. Conversely, t11-18:1 and c9,t11-CLA showed either no relationship (r = -0.026, P >0.10) or a positive relationship (r = 0.4, P< 0.001) to cMUFA:SFA in backfat, respectively. Our findings suggest that neither yield nor quality grades impact the cMUFA;SFA ratio which may negatively affect beef fat quality and healthfulness. The negative correlation between cMUFA:SFA and the concentrations of t10-18:1 and t10,c12-CLA in backfat suggests that conditions leading to increased ruminal production of these biohydrogenation intermediates may prevent feedlot cattle from reaching their potential for higher cMUFA:SFA. Cause-and-effect studies are needed to determine the extent to which trans-10 biohydrogenation intermediates affect cMUFA:SFA ratio in beef fat.