view - Department of Reproduction, Obstetrics and Herd Health

MILK FAT SATURATION AND REPRODUCTIVE PERFORMANCE IN DAIRY CATTLE
We demonstrated a negative association between the milk UFA content and the
CRFI which, together with the aforementioned increased DIMFI, results in higher
DIMCONC. In vivo observations on conception rates (CR) and milk UFA when
supplementing FA to dairy cows are scarce and contradicting. On top, our results show
an association with the average herd bulk tank UFA per year, whereas experiments
supplementing UFA have often targeted specific supplementation during the prebreeding
or breeding period which makes comparison to our data intruiging.
Nevertheless, the observation of a more unsaturated FA profile of follicular fluid, oocytes
and granulosa cells in winter as an explanation for seasonal differences in dairy cow
fertility (Zeron et al., 2001), has triggered in vivo research to increase the UFA content of
reproductive tissues. Many diverse experiments with supplemental UFA have tried to
increase CR in dairy cows. Compared to a source of SFA, feeding flaxseed and sunflower
seeds increased the UFA content in granulosa cells and milk fat respectively (Zachut et
al., 2010). Subsequently, the number of follicles aspirated during ovum pickup and the
subsequent cleavage rate of collected oocytes in the flaxseed fed cows was increased
whereas cows fed sunflower had a lower proportion of grade 1 oocytes. Fouladi-Nashta
et al. (2009) increased milk UFA by feeding both full fat toasted soybean or extruded
linseed. Although a higher PUFA content was found in granulosa cells for the soybean
group, they were unable to show any differences in blastocyst yield or embryo quality
compared with SFA. The authors concluded that bovine ovaries are able to buffer
oocytes against FA fluctuations, only modestly affecting their developmental potential.
Furthermore, increasing the level of UFA in milk by feeding rolled sunflower seeds
compared with rolled flaxseed has been associated with a higher pregnancy loss and
tendency for a lower CRFI (Ambrose et al., 2006). The latter studies illustrate the
diversity in reproductive studies supplementing FA from different sources (saturated FA
vs. soybean vs. linseed) and different treatments (toasted vs. extruded vs. rolled) as
comprehensively reviewed by Gulliver et al. (2012). When Petit et al. (2001) compared a
mixture of SFA/UFA (calcium salts of FA (Megalac) plus flaxseed meal) to an UFA source
(formaldehyde treated whole flaxseed) in an experiment with 30 cows, they found an
increased CRFI (87.5 vs. 50%) in cows fed whole flaxseed. When Fuentes et al. (2008)
tried to repeat the results of the previous study, they were not able to find any
differences in reproductive performance on a total of 356 cows fed either a mixture of
SFA/UFA (calcium salts of 16:0 and extruded soybeans) or extruded flaxseed. This nicely
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