The effect of the change from a herbage- to a concentrate-based diet on the oxidative stability of raw and cooked lamb meat

- Finishing pasture-raised lambs on concentrates increased meat lipid oxidation.
- The diet did not affect the concentration of pro-oxidant fatty acids in muscle.
- Finishing lambs on concentrates could impair the antioxidant capacity of muscle.
- Meat colour was stable over storage and was slightly affected by the diet.

Over 89 days, 10 lambs (S) were fed concentrates and hay in stall, while 9 lambs (P) grazed at pasture. Two groups of 9 animals grazed at pasture until switching to a concentrate-based diet for 14 or 37 days before slaughter (P-S14 and P-S37). The fat content of longissimus dorsi muscle (LM) increased with increasing duration of concentrate feeding (P = 0.05). As a consequence, the concentration of polyunsaturated fatty acids (PUFA) and of the highly peroxidisable (HP) PUFA in the polar lipids was similar between treatments. Lipid oxidation in fresh LM over 8 days of storage was affected by the diet (P < 0.0005) with the P-S37 and P treatments producing, respectively, the highest and the lowest TBARS values. The P treatment reduced TBARS in cooked minced LM over 2 days of storage and no difference was found between the P-S14, P-S37 and S treatments. Colour stability of fresh LM was not noticeably affected by the dietary treatment.