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.

After giving birth to a calf, cows, like other mammals, experience a period of very high energy expenditure, which is often associated with negative energy balance (NEB) or metabolic stress. NEB, among others, decreases the reproductive ability of the cow. In dairy cattle, it is required that both a high milk yield is achieved, and the cow is able to conceive again as soon as possible. Thus, the levels of markers of metabolic stress, namely total cholesterol (tChol), nonesterified fatty acids (NEFA), beta-hydroxybutyrate (BHB), and triacylglycerols (TAGs), were monitored to see whether their level correlate with the reproduction capability of primiparous dairy cows and whether these molecules can be used as markers of readiness of the cow to conceive. It was shown that there is high correlation between NEFA, BHB, and TAGs levels and reproduction capability of the primiparous dairy cow. On the other hand, the impact of tChol is very ambiguous.

• Klíčová slova
• cumulus cells, metabolic stress, negative energy balance, oocyte aspiration, oocyte quality, primiparous dairy cows,
• MeSH
• biologické markery krev   MeSH
• kyselina 3-hydroxymáselná * krev   MeSH
• kyseliny mastné neesterifikované * krev   MeSH
• oocyty fyziologie   MeSH
• parita MeSH
• rozmnožování * fyziologie   MeSH
• skot fyziologie   krev   MeSH
• těhotenství MeSH
• triglyceridy * krev   MeSH
• zvířata MeSH
• Check Tag
• skot fyziologie   krev   MeSH
• těhotenství MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• biologické markery MeSH
• kyselina 3-hydroxymáselná * MeSH
• kyseliny mastné neesterifikované * MeSH
• triglyceridy * MeSH

The objective of this study was to evaluate the influence of negative energy balance on fatty acids proportion in the milk of Czech Fleckvieh cows after calving. Milk quality was determined based on fatty acid group proportion. Milk quality was evaluated in relation to selected negative energy balance (NEB) traits: body condition change (DEC) and milk citric acid content (CAC) after calving. Milk samples (n = 992) were collected once per week from 248 Czech Fleckvieh cows during the first month of lactation. Fatty acid content (%) in milk samples was determined and results were grouped as saturated (SFA) (hypercholesterolemic or volatile fatty acids) or unsaturated (UFA) (monounsaturated or polyunsaturated). Our results showed that cows with a deep NEB produce milk that is healthier for human consumption. Cows with a more significant DEC or the highest level of CAC in milk had the lowest proportion of SFA and the highest proportion of UFA (p < 0.01). These cows experienced higher physiological stress after calving; however, they produced milk of higher nutritional quality. Nowadays, we can see preventive efforts to mitigate NEB periods as a result of modern breeding trends regarding vitality, robustness, or longevity.

• Klíčová slova
• Czech Fleckvieh cows, body condition score, citric acid, lipo-mobilisation, nutritional value,
• Publikační typ
• časopisecké články MeSH