Mobilization of fatty acids from adipose tissue during metabolic stress will increase the amount of free fatty acids in blood and follicular fluid and, thus, may affect oocyte quality. In this in vitro study, the three predominant fatty acids in follicular fluid (saturated palmitic and stearic acid and unsaturated oleic acid) were presented to maturing oocytes to test whether fatty acids can affect lipid storage of the oocyte and developmental competence postfertilization. Palmitic and stearic acid had a dose-dependent inhibitory effect on the amount of fat stored in lipid droplets and a concomitant detrimental effect on oocyte developmental competence. Oleic acid, in contrast, had the opposite effect, causing an increase of lipid storage in lipid droplets and an improvement of oocyte developmental competence. Remarkably, the adverse effects of palmitic and stearic acid could be counteracted by oleic acid. These results suggest that the ratio and amount of saturated and unsaturated fatty acid is relevant for lipid storage in the maturing oocyte and that this relates to the developmental competence of maturing oocytes.

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-This review addresses the suggestion that the decline in dairy reproductive performance, as increasingly observed these days, may be due to a hampered process of metabolic adaptation in early lactating cows. In our opinion, adaptation to the negative energy balance is a gradual process. Because almost all cows do adapt in the long run, it is not possible to classify animals as adapted or non-adapted. The use of risk factors is more appropriate in this case and is discussed in this review. Among them are the body condition score and its derivatives, feed intake, the calculated negative energy balance, and metabolic parameters like the plasma concentration of insulin or the triacylglycerol content in the liver. Moreover, factors that play a role in the link between declined reproductive performance and the metabolic situation of the cow during the early lactating period are discussed. Among these are insulin, insulin-like growth factors, leptin, neuropeptide Y, nonesterified fatty acids, thyroïd hormones, urea, and ammonia. fertility / dairy / periparturient metabolic adaptation / physiopathology / periparturition

Metabolic conditions characterized by elevated free fatty acid concentrations in blood and follicular fluid are often associated with impaired female fertility. Especially elevated saturated fatty acid levels can be lipotoxic for several somatic cell types. The aim of this study was to determine the impact of elevated free fatty acid concentrations in follicular fluid on neutral lipids (fatty acids stored in lipid droplets) inside cumulus cells and oocytes and their developmental competence. To this end, cows were exposed to a short-term fasting period during final oocyte maturation. This resulted in elevated, but distinct, free fatty acid concentrations in blood and follicular fluid and a rise in the concentrations of in particular fatty acids with a chain length of 14-18 carbon atoms. Interestingly, elevated free fatty acid concentrations in follicular fluid resulted in a massive increase in the level of neutral lipids in cumulus cells, whereas the level of neutral lipid in oocytes was hardly affected. Furthermore, competence of oocytes to develop to the blastocyst stage after fertilization and culture of cumulus-oocyte-complexes of the experimental and control group was not different. In conclusion these data suggest that short-term elevated free fatty acid concentrations in follicular fluid do not harm oocyte developmental competence. We propose that the involvement of high levels of mobilized oleic acid in follicular fluid in combination with the induced lipid storage in cumulus cells serves to prevent harmful saturated fatty acid exposure to the oocyte.

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