Efficiency of extruded linseed for the finishing of grass-fed steers to counteract a decline of omega-3 fatty acids in the beef

Effects of different finishing regimes with and without conventional or linseed-supplemented concentrate on growth performance and carcass composition of grass-fed steers as well as meat quality and lipid composition of the beef were investigated. Limousin × Brown Swiss and Limousin × Holstein–Friesian crossbred steers were fed on a grass-based forage-only diet up to an average live weight of 470 kg and an age of 18 months. During the following finishing period, two groups received 3 kg/day of concentrate additional to fresh grass and hay. One concentrate was a conventional cereal-based type (CC) the other contained extruded linseed (LS). Steers of these two groups were fattened to 560 kg of live weight. Two other groups further on received only grass and hay and were slaughtered either at the same average weight (G₁) or at the same age (G₂) as CC steers. The concentrate supplementation in the finishing period did not significantly increase average daily gains of the steers. The killing-out percentage was improved by CC, which was reflected in heavier hot carcasses. No other carcass quality trait was significantly affected by the different feeding regimes. The direct comparison of G₂ with CC showed a significantly higher shear force and compression energy in m. longissimus dorsi (LD) of G₂, suggesting a less tender LD, but not m. biceps femoris (BF), of the grass-fed steers. In the groups compared at the same slaughter weight, no significant differences were observed in meat colour and texture. Lower proportions of C18:3n-3 (omega-3) in total lipids and in phospholipids of LD and BF were found for CC steers compared to grass-fed steers. This effect was partly compensated for by the supplementation of linseed to the concentrate which also exerted a trend towards higher levels of conjugated linoleic acid. However, since the n-6/n-3 ratio in the beef of the CC steers was still favourably low, it remains a matter of economic calculations and marketing considerations to determine whether linseed supplementation might be a cost-efficient measure in pasture beef programs to produce meat with claimed dietetic advantages in terms of fatty acid composition.