Short Communication: Erythrocytes assayed early ante mortem can predict adipose tissue and muscle trans-18:1 isomeric profiles of steers fed red clover silage supplemented with flaxseed

Trans-10 18:1 in ruminant meats: A review

Trans (t) fatty acids (TFA) from partially hydrogenated vegetable oils (i.e., industrial trans) have been phased out of foods in many countries due to their promotion of cardiovascular disease. This leaves ruminant-derived foods as the main source of TFA. Unlike industrial TFA where catalytic hydrogenation yields a broad distribution of isomers, ruminant TFA are enzymatically derived and can result in enrichment of specific isomers. Comparisons between industrial and ruminant TFA have often exonerated ruminant TFA due to their lack or at times positive effects on health. At extremes, however, ruminant-sourced foods can have either high levels of t10- or t11-18:1, and when considering enriched sources, t10-18:1 has properties similar to industrial TFA, whereas t11-18:1 can be converted to an isomer of conjugated linoleic acid (cis(c)9,t11-conjugated linoleic acid), both of which have potential positive health effects. Increased t10-18:1 in meat-producing ruminants has not been associated with negative effects on live animal production or meat quality. As such, reducing t10-18:1 has not been of immediate concern to ruminant meat producers, as there have been no economic consequences for its enrichment; nevertheless at high levels, it can compromise the nutritional quality of beef and lamb. In anticipation that regulations regarding TFA may focus more on t10-18:1 in beef and lamb, the present review will cover its production, analysis, biological effects, strategies for manipulation, and regulatory policy.

Red blood cells are superior to plasma for predicting subcutaneous trans fatty acid composition in beef heifers

The trans (t)-18:1 content in beef has become more of interest as partially hydrogenated vegetable oils are removed from foods. Predicting t-18:1 early in the feeding period would be useful if limitations are put on t-18:1 in beef. To determine which blood component is better related to backfat, proportions of t10-18:1 and t11-18:1 (vaccenic acid) were measured in heifer red blood cells (RBC) and plasma (N = 14) after 0, 28, 56, and 76 d on a barley-grain-based diet, and correlated with post-slaughter subcutaneous fat (SCF). Total t-18:1 declined in both RBC and plasma during late finishing (P < 0.05). At 28 d, t11-18:1 decreased and t10-18:1 increased in RBC and plasma (P < 0.05). By 76 d, t10-18:1 declined to 0 d levels. RBC and plasma t-18:1 compositions were highly correlated (t10-18:1, r ≥ 0.7, P ≤ 0.02; t11-18:1, r ≥ 0.51, P ≤ 0.06). Correlations with post-slaughter backfat were, however, consistently greater for RBC compared with plasma. The use of RBC t-18:1 composition may, therefore, be superior to plasma for predicting t-18:1 in SCF, and the length of finishing could be useful for manipulating t-18:1 in beef. The time required for changes in t18:1 in RBC to reflect in changes in SCF still, however, needs to be determined to establish optimal durations for beneficial modification.

Feeding steers hay with extruded flaxseed together or sequentially has a profound effect on erythrocyte trans 11-18:1 (vaccenic acid)

Extruded flaxseed and ground hay [25% and 75%; dry matter (DM) basis] were fed in a total mixed ration (TMR) or sequentially (non-TMR) to three pens of eight crossbred steers per diet. At 112 d, erythrocytes from non-TMR steers had 65% more vaccenic acid (trans 11-18:1) than TMR steers (P < 0.05).

Subcutaneous adipose fatty acid profiles and related rumen bacterial populations of steers fed red clover or grass hay diets containing flax or sunflower-seed

Steers were fed 70∶30 forage∶concentrate diets for 205 days, with either grass hay (GH) or red clover silage (RC), and either sunflower-seed (SS) or flaxseed (FS), providing 5.4% oil in the diets. Compared to diets containing SS, FS diets had elevated (P<0.05) subcutaneous trans (t)-18:1 isomers, conjugated linoleic acids and n-6 polyunsaturated fatty acid (PUFA). Forage and oilseed type influenced total n-3 PUFA, especially α-linolenic acid (ALA) and total non-conjugated diene biohydrogenation (BH) in subcutaneous fat with proportions being greater (P<0.05) for FS or GH as compared to SS or RC. Of the 25 bacterial genera impacted by diet, 19 correlated with fatty acids (FA) profile. Clostridium were most abundant when levels of conjugated linolenic acids, and n-3 PUFA's were found to be the lowest in subcutaneous fat, suggestive of their role in BH. Anerophaga, Fibrobacter, Guggenheimella, Paludibacter and Pseudozobellia were more abundant in the rumen when the levels of VA in subcutaneous fat were low. This study clearly shows the impact of oilseeds and forage source on the deposition of subcutaneous FA in beef cattle. Significant correlations between rumen bacterial genera and the levels of specific FA in subcutaneous fat maybe indicative of their role in determining the FA profile of adipose tissue. However, despite numerous correlations, the dynamics of rumen bacteria in the BH of unsaturated fatty acid and synthesis of PUFA and FA tissue profiles require further experimentation to determine if these correlations are consistent over a range of diets of differing composition. Present results demonstrate that in order to achieve targeted FA profiles in beef, a multifactorial approach will be required that takes into consideration not only the PUFA profile of the diet, but also the non-oil fraction of the diet, type and level of feed processing, and the role of rumen microbes in the BH of unsaturated fatty acid.