The serum levels of triacylglycerols, nonesterified fatty acids, and beta-hydroxybutyrate as markers of reproductive capability of primiparous dairy cows.

Metabolic stress and negative energy balance (NEB) are typical undesirable accompanying phenomena of the postpartum period in dairy cattle. They negatively affect not only milk production but also the reproductive abilities of the cow, and it is therefore desirable to recognize NEB early to prevent its development. Metabolic stress markers are traditionally total cholesterol (tChol), nonesterified fatty acids (NEFA), beta-hydroxybutyrate (BHB), and triacylglycerols (TAGs). The aim of this work was to determine whether the level of the aforementioned markers in the blood correlates with the ability of a primiparous dairy cow to conceive soon after the first calving. Therefore, oocytes were collected from the monitored cows shortly after calving using the ovum pick-up method, and their quality was subsequently determined. We observed cumulus cell expansion, oocytes quality, maturation rate, and the amount and distribution of lipids within the oocyte. In addition to the mentioned markers, we also monitored the effect of the season in which aspiration was performed to assess its impact on the reproductive indicators of the monitored cows. We observed a negative correlation between higher TAGs and oocyte maturation rate, while the number of aspirated oocytes per cow and the fertilization capability were positively associated with TAGs. Additionally, higher BHB levels in the blood were linked to enhanced fertilization capability. The higher levels of TAGs, BHB, and NEFA in blood were associated with increased lipid intensity, and higher lipid content was positively correlated with both the quality of cumulus cells and oocytes. In summary, we found that NEFA, BHB, and TAGs are the most reliable markers of a cow's readiness to become pregnant after her first calving. The use of tChol, however, remains very controversial. Moreover, primiparous cows are more prepared for re-pregnancy in the warmer season.