Cows at the beginning of lactation often do not meet their energy needs by feeding and therefore mobilize body fat, which produces ketone bodies, including β-hydroxybutyrate (BHB). They are nevertheless usually inseminated around 60 d postpartum, when they are still in this characteristic period of energy deficit. The aim of this study was to observe the effects of negative energy balance on embryo quality and to identify ways to improve the fertility of dairy cows. Holstein cows (n = 18) grouped as high or low BHB based on blood measurement at day 45 postpartum were estrus-synchronized and treated with follicle-stimulating hormone to obtain multiple follicle development, induced to ovulate and inseminated with sexed semen around day 60 postpartum. Of the 290 embryos collected over 16 mo, 159 were of quality I to IV. Based on microarray analysis of gene expression, exposure to an energy deficit metabolic environment (high BHB) during early development appeared to modify signaling by the mTOR and sirtuins pathways in the embryo, implying mitochondrial dysfunction and inhibition of transcription, leading to slower cell division, thus programming the embryo to be more energy efficient. Altered methylation markers suggested that such coping mechanisms might persist into adulthood.
Keywords: Dairy cows; Embryo quality; Energy balance; Epigenetics; Metabolism.
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