view - Department of Reproduction, Obstetrics and Herd Health

MILK FAT SATURATION AND REPRODUCTIVE PERFORMANCE IN DAIRY CATTLE
INTRODUCTION
Continuous research in dairy cattle has focused on the link between nutrition and
the on-going decline in high producing dairy cow fertility (Thatcher et al., 2011). Specific
long chain fatty acids (LCFA), and not fat per se, have gained general recognition as
being essential for important mammalian reproductive functions including effects on
membrane fluidity, intracellular cell-signalling cascades and susceptibility for oxidative
injury (Staples and Thatcher, 2005). Typically, dairy cattle diets contain approximately
2.0% of LCFA, predominantly polyunsaturated (Staples et al., 1998). The main FA in
most seed lipids is 18:2n-6 (linoleic acid) whereas 18:3n-3 (linolenic acid) predominates
in most forage lipids (Palmquist and Jenkins, 1980). These FA cannot be synthesised by
the mammalian cells due to the lack of desaturase enzymes to incorporate a double bond
beyond the ninth carbon in the acyl chain (Gurr et al., 2002). Combined with the limited
supply of unsaturated FA (UFA) to the small intestine associated with the extensive
biohydrogenation in the rumen (Jenkins et al., 2008), UFA have been proposed by
researchers as nutraceuticals in the bovine to ameliorate dairy cow fertility (Santos et al.,
2008; Silvestre et al., 2011; Thatcher et al., 2011).
Experiments focusing on the direct effect of specific FA on oocyte maturation and
embryonic development have opened new perspectives to the knowledge of FA feeding.
More specifically, Leroy et al. (2005) and van Hoeck et al., (2011) showed detrimental
effects of saturated FA during oocyte maturation on subsequent oocyte and embryonic
development as compared to their unsaturated counterparts in an in vitro maturation
model. Fatty acid supplementation during in vitro bovine oocyte maturation showed
contrasting results as 18:2n-6 and 18:3n-3 respectively hampered (Marei et al., 2010)
and enhanced (Marei et al., 2009) the nuclear maturation rate and subsequent
developmental potential of oocytes. Furthermore, post-thawing in vitro embryo survival
was improved by supplementation of 20:4n-6 or 20:5n-3 during oocyte maturation
(Marques et al., 2007). Al Darwich et al. (2010) observed a tendency for a lower
blastocyst yield with increasing 18:3n-3 addition during in vitro embryo culture and a
detrimental effect of embryo culture with the highest dose of 22:6n-3 and 18:2 trans-10,
cis-12 on in vitro survival after vitrification and warming. The in vivo observation of a
more UFA profile of follicular fluid, oocytes and granulosa cells in winter which might
explain seasonal differences in dairy cow fertility (Zeron et al., 2001), has opened the
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