view - Department of Reproduction, Obstetrics and Herd Health

CHAPTER 5.2
prepartum period. At the onset of lactation, most likely due to formation of eicosanoid
products of the prostaglandin series (Guilbault et al., 1984), the animals in the SHORT
and CON group similarly decrease in 20:4n-6 in all blood fractions which was
subsequently mirrored in FF and MF during the first 2 weeks of lactation. The response
lag up to 2 weeks of 20:4n-6 supplementation to appear in BP for LONG has been
reported in humans for 20:5n-3 as well (Cartwright et al., 1985; Sanders and Hinds,
1992). Overall BP 20:4n-6 remained higher compared with SHORT and CON, but despite
continuous dietary supplementation, gradually decreased from week 1 to 2 in lactation.
In contrast, switching to n-3 at 14 DIM, immediately increased 18:3n-3
concentration two-fold in BP, FF and MF for SHORT at the end of the supplementation
period and over a three-fold for the 22:6n-3 in BP, FF and MF for LONG. Peripartal
supplementation up to 92 g/kg DM of extruded flaxseed increased 5.3-fold in BP, 5.1-
fold in MF (Zachut et al., 2010a) and 8.1-fold in FF collected at 63 and 96 DIM (Zachut et
al., 2011). Flaxseed, after various treatments (Mustafa et al., 2003; Petit et al., 2004;
Gonthier et al., 2005) provoked similar changes in BP as observed in our study. Also, in
more established lactation (114 DIM), similar results were obtained for BP and FF when
feeding extruded flaxseed at dietary inclusion rate of 38 g/kg DM, but increases in MF
18:3n-3 were smaller (6.6-fold increase; Zachut et al., 2010b). From our results it can be
concluded that feeding smaller amounts of 18:3n-3 is primarily reflected in the 18:3n-3
content in TAG. As the latter fraction is a major source of milk FA (Bauman and Griinari,
2003), this might explain the faster response in 18:3n-3 MF before changes are observed
in BP and FF when feeding smaller amounts of flaxseed (Zachut et al., 2010b). In
contrast, a clear TAG enrichment seems to occur for 22:6n-3 when fed at lower rates,
possibly explaining the 3-fold increase in MF compared with a 2-fold for 18:3n-3.
Furthermore, Offer et al. (2001) proved this enrichment to primarily occur in CE, NEFA
and PL fraction in high-density lipoproteins (HDL), and TAG and PL in low-density
lipoproteins (LDL) but not the very low-density lipoproteins (VLDL). Mammary
lipoprotein lipase primarily affects the TAG fraction of chylomicrons and VLDL to obtain
FA for MF synthesis (Palmquist and Mattos, 1978; Moore and Christie, 1979; Barber et
al., 1997) explaining the low concentration of 22:6n-3 in MF compared to BP and FF.
Compared to earlier work, we fed less than 20 g of 22:6n-3 as opposed to studies
supplementing over 40 g per day of 22:6n-3 with concomitant 10 times higher 22:6n-3
concentration in MF (Boeckaert et al., 2008; Hostens et al., 2011). Limited research has
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