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The consequences of metabolic changes in high-yielding dairy cows on oocyte and embryo quality*

Published online by Cambridge University Press:  01 August 2008

J. L. M. R. Leroy*
Laboratory for Veterinary Physiology, Department of Veterinary Sciences, Faculty of Biomedical, Pharmaceutical and Veterinary Sciences, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk, Belgium
A. Van Soom
Department of Reproduction, Fertility and Herd Health; Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820 Merelbeke, Belgium
G. Opsomer
Department of Reproduction, Fertility and Herd Health; Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820 Merelbeke, Belgium
P. E. J. Bols
Laboratory for Veterinary Physiology, Department of Veterinary Sciences, Faculty of Biomedical, Pharmaceutical and Veterinary Sciences, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk, Belgium
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Unsatisfactory reproductive performance in dairy cows, such as reduced conception rates, in addition to an increased incidence of early embryonic mortality, is reported worldwide and has been associated with a period of negative energy balance (NEB) early post partum. Typically, NEB is associated with biochemical changes such as high non-esterified fatty acid (NEFA), high β-hydroxybutyrate (β-OHB) and low glucose concentrations. The concentrations of these and other metabolites in the follicular fluid (FF) of high-yielding dairy cows during NEB were determined and extensively analyzed, and then were replicated in in vitro maturation models to investigate their effect on oocyte quality. The results showed that typical metabolic changes during NEB are well reflected in the FF of the dominant follicle. However, the oocyte seems to be relatively isolated from extremely elevated NEFA or very low glucose concentrations in the blood. Nevertheless, the in vitro maturation models revealed that NEB-associated high NEFA and low glucose levels in the FF are indeed toxic to the oocyte, resulting in deficient oocyte maturation and developmental competence. Induced apoptosis and necrosis in the cumulus cells was particularly obvious. Furthermore, maturation in saturated free fatty acid-rich media had a carry-over effect on embryo quality, leading to reduced cryotolerance of day 7 embryos. Only β-OHB showed an additive toxic effect in moderately hypoglycemic maturation conditions. These in vitro maturation models, based on in vivo observations, suggest that a period of NEB may hamper the fertility of high-yielding dairy cows through increased NEFA and decreased glucose concentrations in the FF directly affecting oocyte quality. In addition to oocyte quality, these results also demonstrate that embryo quality is reduced following an NEB episode. This important observation may be linked to the typical diet provided to stimulate milk yield, or to physiological adaptations sustaining the high milk production. Research into this phenomenon is ongoing.

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Copyright © The Animal Consortium 2008

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This invited paper was presented at BSAS meeting ‘Fertility in Dairy Cows – bridging the gaps’ 30–31 August 2007, Liverpool Hope University.


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