Indoor fattening of lambs raised on pasture: 2. Influence of stall finishing duration on triglyceride and phospholipid fatty acids in the longissimus thoracis muscle.

Twenty-four male Ile-de-France lambs (six blocks of homologous lambs) were used to study the effect of four feeding systems on muscle triglyceride (TG) and phospholipid (PL) fatty acids (FA) from the longissimus thoracis (LT): raised and finished on cool season grasses (G), raised on the same grasses and stall-finished, indoors, on concentrates and hay, respectively, for 22 (GSS) and 41 days (GSL), and stall-feeding, indoors, on concentrate and hay during both growing and finishing periods (S). In TG, similar decreases (P<0.05) of proportions of linolenic acid were observed after changing from grass feeding to stall feeding (GSS and GSL), and a decrease (P<0.05) in proportions of conjugated C18:2 cis9, trans11 (CLA cis9, trans11) was obtained after a long period of concentrate feeding (GSL). In PL, C22:5 n-3 achieved a significantly (P<0.05) lower level in GSL lambs compared both G and S lambs. A similar non-significant tendency was observed in the case of the other very long chain n-3 polyunsaturated FA. The separate analysis of fatty acids of TG and PL from the LT muscle underlined that TG afforded a more significant lowering effect than PL on the overall ratio between C18:2 n-6 and C18:2 n-3 in muscle lipids and on the health potential of meat for the consumer. A PCA analysis combining FA composition of TG and PL, and growth performances of the lambs allowed an efficient discrimination between the four feeding systems.

Indoor fattening of lambs raised on pasture. Part 1: Influence of stall finishing duration on lipid classes and fatty acids in the longissimus thoracis muscle.

Forty male Ile-de-France lambs (10 blocks of 4 homologous lambs) were used to study the effects of four feeding systems on muscle fatty acids (FA): raising and finishing on cool-season grasses (G), raising on the same grasses and stall-finishing, indoors, on concentrates and hay, respectively, for 22 (GSS) or 41 days (GSL), and stall-feeding indoors on concentrates and hay during both growing and finishing periods (S). Twenty-four lambs only (6 blocks) were retained for comparison of growth performances, lipid content in the longissimus thoracis muscle (LT) and their FA composition according to treatment. The 16 other lambs (4 blocks) were removed from the comparison, due to a large spread in the growth of the lambs towards the end of the trial. No significant effects of treatment were seen on the rate of growth (221, 228, 243 and 245±SE 8.0g/d, respectively, for G, GSS, GSL and S groups), and the lipid contents of the LT (2.22, 2.16, 2.17 and 2.52±SE 0.11g/100g fresh tissue). Grazing, lowered n-6 PUFA (polyunsaturated fatty acids), and increased n-3 PUFA and C18:2 c9t11 (conjugated linoleic acid cis9, trans11) compared to concentrate feeding. The main effects of grazing were not removed by a short period of finish indoors on concentrate (GSS group), but C20:4 n-6 and C22:6 n-3 contents achieved the lowest contents in this group, with significant differences from the values observed for GSL and S groups (C20:4 n-6) or from the three other groups (C22:6 n-3). After a longer period of finish on concentrate (GSL group), C18:3 n-3 (linolenic acid), C18:2 c9t11 and long chain (LC) n-3 PUFA were brought to the levels observed in the S group. In terms of adequacy for human health, the C18:2 n-6/C18:3 n-3 ratios were favourably low in the four groups (2.6, 3.6, 4.9 and 5.2±SE 0.7, respectively, for G, GSS, GSL and S groups), the level observed in the case of G group being significantly lower than for the three other groups and the level observed for GSS group being significantly lower than for the GSL and S groups.