Negative Energy Balance Influences Nutritional Quality of Milk from Czech Fleckvieh Cows due Changes in Proportion of Fatty Acids

SIMPLE SUMMARY: The intensity of negative energy balance period could potentially affect milk quality, mainly through its influence on milk composition. Fatty acid composition in milk affects its nutritional value for human consumption, because individual fatty acids have various effects on the human organism. The aim of our study was to describe the influence of negative energy balance on fatty acids proportion in milk of Czech Fleckvieh cows. Our results showed that cows in deep negative energy balance produced milk with a healthier proportion of fatty acids from a human nutrition standpoint. These cows experienced higher physiological stress after calving and are more susceptible to diseases and premature culling. Nowadays, farmers demand healthier and less problematic cows, while consumers ask for improved welfare and nutritionally balanced dairy products. However, using this phenomenon to improve nutritional value of milk might be opposed by consumers, farmers and even current breeding goals. These are currently focused on improving vitality, robustness, and longevity of dairy cows. ABSTRACT: 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.