The experiment was conducted to analyse the effect of fermented acid whey permeate on milk yield and composition in the lactating cows. Propionic acid bacteria and their metabolites have been used in the lactating cows feeding over decades, primarily to improve growth performance, feed conversation and milk production efficiency. Two groups of the lactating cows were arranged in the study: control group (n=50) and experimental group (n=50). Experimental group’s animals received 0.5 L of fermented whey permeate daily. Acid whey permeate was inoculated with the freeze-dried PS-4 (Propionibacterium freudenreichii subsp. shermanii, Chr.Hansen, Denmark) starter and fermented anaerobically for 48 hours at 20±2 ºC. Fat, protein, lactose and total solids concentration in acid whey permeate and fermented acid whey permeate was analysed by the standard methods, but propionic acid was detected by HPLC. Milk composition and quality indices were determined at the beginning of the study and each month during 6 months period. At the end of the study the feeding of fermented acid whey permeate was stopped, but milk composition and quality data were monitored additionally after one month. Milk fat, protein, lactose, total solids, urea concentration and somatic cell count were analysed by a near infrared spectroscopy. The variability in milk composition and quality data across trial was greater in the experiment group than in the control. Milk fat and somatic cell count were significantly different (p is less than 0.05) than other studied parameters in the experimental group cows’ milk. Milk yield and lactose concentration were tended to increase during feeding of fermented acid whey permeate in the lactating cows without significant differences between control and experimental groups. Fermented acid whey permeate as feed supplement improves energy metabolism for dairy cows which results in the higher milk yield and fat concentration.

Organic fermented milk products are an area of interest combining functional properties and sustainable practices. Limited information is available regarding the specific components of organic milk that may impact the growth of lactic acid bacteria. This study emphasised the differences in bioactive compounds between organic and conventional milk and their potential influence on lactic acid bacteria growth. Analysis of organic (n = 15) and conventional (n = 15) farm milk using GC-MS revealed differences in fatty acid (FA) concentrations, mainly mono-, polyunsaturated fatty acids, and conjugated linoleic acid. Individual FA, such as stearic, linoleic, and oleic acids, were up to 33.6%, 31.0%, and 25.23% higher in conventional milk. Detection of the whey proteins using the enzyme-linked immunosorbent assay (ELISA) showed lysozyme content was up to 40.6% higher in conventional (22.04 µg L⁻¹) than in organic (15.68 µg L⁻¹) milk. Conversely, lactoferrin content was 20.4% higher in the organic (45.27 µg L⁻¹) than in conventional (36.04 µg L⁻¹). No difference in the content of immunoglobulin A was found. The higher concentrations of lysozyme, mono- and polyunsaturated fatty acids in conventional milk could enhance a higher inhibitory activity against lactic acid bacteria compared to organic milk.