Feeding Extruded Linseed or Soybean and Hay Free-Choice to Rubia Gallega Young Heifers Does Not Substantially Alter Health-Enhancing Fatty Acids in Meat

Context A common strategy to try and improve the fatty acid (FA) composition of meat and fat from cattle has been to feed protected oil or oilseeds. Aims Concentrate containing 4.5% fat from vegetable oil, extruded linseed or extruded soybean were fed free-choice with hay to Rubia Gallega heifers to examine the effects on meat (Longissimus thoracis (LT)) and subcutaneous fat (SCF) FAcompositions, and effects on meat and carcass quality. A secondary aim was to assess treatment effects on levels of specific desirable FAs in meat and fat. Methods Twenty-four 7-month-old Rubia Gallega heifers were assigned to three experimental diets: control concentrate (with palm oil) or concentrates containing either extruded linseed (LS) or extruded soybeans. Concentrates and hay were fed for 90 days before slaughter at an average age and weight of 300 days and 350 kg, respectively. Key results Minor treatment effects on animal performance, carcass traits and meat quality were noted. Relative to the control concentrate diet, feeding the linseed diet led to a slight increase in α-linolenic acid (18:3n-3) in SCF (P < 0.001), no change in 18:3n-3 in LT, reduced n-6/n-3 ratios in both LT and SCF (LT, P < 0.01; SCF, P < 0.001), and avoided ∑(t6- to t10-)18:1 accumulation in either tissue (LT, P = 0.017; SCF, P < 0.05). Conclusions Although FA improvements when feeding linseed could be viewed as positive for human health, quantitatively, feeding extruded oilseeds and hay free-choice were ineffective at creating rumen conditions needed to substantially enrich n-3 polyunsaturated FAs (PUFA) or desirable biohydrogenation intermediates in LT. Implications To produce high-quality Rubia Gallega meat with meaningful and consistent enrichments of polyunsaturated FAs and beneficial biohydrogenation products will require more efficient methods for ruminal protection of PUFA, and further investigations into the timing and amounts of PUFA-enriched concentrate feeding.