Oil contents and fatty acid profiles
Table 2 presents the total oil concentration and the FA profiles of
saturated FAs (SFAs) and unsaturated FAs (UFAs). Total oil
concentrations ranged from 30.10% to 45.11% of DM, with values under
LS being significantly higher on average (41.3%DM) than values under HS
(34.9%DM) (p<0.001 ). For a given T-modality, S effects
were significant except for T-control (Table 2). Effects of T-modalities
were also observed (p<0.05 ), although they were not
significant under LS. Under HS, all T-modalities negatively impacted
total oil concentration with mod1 and mod3 displaying the greatest
decreases (-23.5% and -20.8%, respectively, compared to the T-control)
followed by mod2 and mod4, thus indicating lower negative effects of
shorter stressing events, whether they were mild (mod2) or included heat
peaks (mod4). The SFA concentration (including C16:0, C18:0, C20:0,
C22:0) and the UFA concentration (including C16:1, C18:1, C18:2, C18:3,
C20:1) ranged from 2.91 to 3.99% of DM and 27.19 to 41.11 % of DM,
respectively. A highly significant S effect was observed in both SFA and
UFA concentrations (for SFAs 3.1% DM in HS and 3.6%DM in LS on average
and for UFAs 31.8 %DM in HS and 37.7 %DM in LS on average). For a
given T-modality, S effects were significant (p<0.05 )
except for T-control (as observed for the total FA concentration) and
mod1. Under HS, no significant T-modality effect was observed on SFA
concentrations, while they varied under LS with mod1 and mod4 displaying
the lowest (-9.1%DM from LS T-control) and highest (+17.3%DM from LS
T-control) values, respectively. The significant T x S effect on SFA
concentrations (p<0.01 ) was mainly due to the different
T-modality rankings observed under LS compared to similar ranking under
HS. In contrast to the SFA concentrations, T-modality effects on UFA
concentrations were observed only under HS, with mod1 and T-control
having the lowest and highest values, respectively (-24.7% of DM for
mod1 compared to T-control). Overall, T-modality effects on total FA and
UFA concentrations were observed only under HS and the effect on SFA
concentrations was only under LS. Mod1 had the greatest impact on
decreasing FA concentrations. Early mild stress did not alleviate the
negative effects of later heat peaks on total FAs, SFAs and UFAs. In
addition, the 4 late heat-peaks sequence had a greater impact than the 3
late heat-peaks sequence under HS (total FAs, UFAs). The S effects on
total FAs, SFAs and UFAs were observed for each T-modality except
T-control (three criteria) and mod1 (SFAs). Eventually, the C18:2/C18:3
ratio (i.e. ω6:ω3 ratio) was significantly impacted by the T-modalities
under HS and LS (Table 2). The highest and lowest ratios were
attributed, respectively, to mod1 and mod2 under HS (+12.8 and -9.9%
compared to the HS T-control) and mod3 and mod2 under LS (+12.6% and
-7.7% compared to the LS T-control). In addition, the 3 late heat-peaks
effect (mod4) was less negative than the early mild stress (mod2). These
results indicated that the number of desaturations decreased with
greater duration of stress exposure (mod1) and intensity and earliness
of the heat stress event (mod3) under both S conditions.