Genetiska och epigenetiska samband mellan näringsförsörjning och fertilitet hos mjölkkor

Sammanfattning: The dairy cow’s ability to resume estrus after calving and to conceive is affected by their metabolic status after calving. For high yielding cows there is a high risk that the feed intake will not be sufficient to cope with the increased energy demands after calving, and the cow will end up in a state of negative energy balance. Energy balance can be measured in various ways, for example by body condition score or by plasma concentration of several metabolic hormones and metabolites. After calving, endocrine pathways stimulate tissue mobilization; insulin signaling is blocked, the concentration of insulin-like growth factor-1(IGF-1) and leptin decreases, and the concentration of growth hormone (GH) increases. This leads to an increase of various metabolites, for example non-esterified fatty acid (NEFA), beta-hydroxybutyrate (BHB) and urea. All these parameters have been negatively associated with several fertility traits, and can probably be used as indirect selection criteria of fertility in breeding programs. Research has also shown that certain genes, associated with fertility and metabolism, are epigenetically regulated. Epigenetics explains variations in gene expression that not originates from the DNA sequence, which implies that better knowledge of epigenetic regulation on fertility traits probably could explain a large part of the genetic variation that is currently unknown. The genetics of metabolic and epigenetic parameters is still only partially investigated in dairy cows and require further study in order to be practically applied in dairy cow breeding.