EN
The study was conducted on Polish Holstein Black-and-White cows. From a herd of about 300 animals maintained in a free-stall dairy shed, two groups of 10 were selected by the analogue method:primiparous (P) and second-lactation cows (SL), taking into consideration the stage of lactation (90±30 days) and daily milk yield (35.42±2,6 kg). During the first 7 days (that were considered the initial period – CTL) all the cows were fed the same TMR (total mixed ration) diet. From day 8 to 28 (considered the true experimental period – FOL) at the same time of the day each cow from both groups received individually 150 g fish oil and 250 g linseed oil. Milk samples were taken individually from each cow three times: on the last day of CTL and on day 14 and day 28 of FOL. As a result of supplementation with FOL, a decrease in the SFA content of milk was observed – for P from 62.610 to 56.70 and for SL from 63.50 to 53.67 g/100g of fat. The milk from P cows after 21 days of supplementation was characterized by a higher level of total CLA (P≤0.01), FFA (P≤0.01), SFA (P≤0.01), SCFA (P≤0.01) as well as atherogenic (AI), thrombogenic (TI) indices (P≤0.01) and lover level of PUFA n-3 (P≤0.01), PUFA n-6 (P≤0.01), LCFA (P≤0.01) and MCFA (P ≤0.01) compared to SL cows. In conclusion, introducing FOL to TMR diets for cows can improve the nutritive value of milk. Differences in the concentration of these milk components between the experimental groups indicate that it is significantly affected by the age of cows.