3.1 | Fatty acid composition of longissimus
dorsi
The relative contents of muscle FAs obtained from the 39 lambs and the
corresponding statistical analysis are shown in Table 2. The highest
percentage FA was oleic acid (C18:1n9), ranging from 33.49% (grazing
group) to 37.93% (stall feeding group). All FAs, with the exception of
SFA (C10:0, C12:0, C14:0, C17:0), MFA (C14:1, C16:1,
C24:1, C22:1n9), PUFA (C20:2,
C18:2n6), significantly varied across
the three feeding modes (Table 2). The grazing treatments for 4 h or 12
h increased (P < 0.01 or P < 0.05) the
proportions of SFAs (i.e., C13:0, C18:0, C21:0, C22:0, C23:0, and
C24:0), but resulted in a lower
(P = 0.002) C16:0 proportion
compared to the control group. In addition, lower (P = 0.012)
proportions of C18:1n9 were found in the grazing and time-limited
grazing treatments. The effect of the feeding regime on the FA content
was calculated, and the data indicated that the grazing treatments
clearly improved almost all PUFAs. For example, the grazing treatment
had the highest proportions of
C18:3n3 (α-linolenic acid, ALA) and
C20:5n3 (timnodonic acid, EPA) compared to the other two treatments
(P < 0.001).
Compared to the other feeding modes,
the grazing treatment had a higher (P < 0.001)
proportion of C22:6n3 (docosahexaenoic acid, DHA) than the other
treatments, which were not significantly different from each other. The
grazing treatment had the highest (P = 0.041; P = 0.004)
proportions of C20:3n6 and C20:4n6 and tended (P = 0.102) to have
increased C18:2n6. Compared with the control, the sum of n-3
polyunsaturated fatty acids (PUFAs) was markedly increased, and the
ratio of n-6/n-3 was decreased from 17.11% to 7.69% after grazing for
4 h or 12h (P < 0.001).