Strusińska D. author Minakowski D. author Pysera B. author Kaliniewicz J. author text journal article 2006 An experiment was performed on 37 Holstein-Friesian cows during the first 120 days of lactation. The cows were fed balanced diets composed of haylage and maize silage (together 52% dry mater) and a concentrate containing 19% crude protein (group 1), a concentrate containing 17.5% crude protein and 1 kg of fat-protein supplement Megapro Plus^® (group 2) or a concentrate containing 19% crude protein and 1 kg of fat-protein supplement Megapro Plus^® (group 3). The mean daily milk yield recorded in groups 2 and 3 amounted to 32.6 kg/d and was by 10.3% higher than in the control group (P ≤ 0.01). FCM yield increased by 15.5% and 12.1% in groups 2 and 3, respectively, in comparison with group 1. Diet supplementation with Megapro Plus^® had no significant effect on the levels of fat, lactose, protein, nitrogen fractions and urea, or some physicochemical properties of milk (density, pH, heat stability). A decrease was noted in solids-non-fat (group 2) and somatic cell count (P ≤ 0.05). Megapro Plus^® supplementation of a diet with a reduced (to 3%) "00" rapeseed meal content in concentrate (group 2) resulted in a significant increase in the concentrations of unsaturated fatty acids (especially C18:1 and C18:2) and hypocholesterolaemic acids (DFA) in milk, recorded on the 120th day of lactation. Megapro Plus^® supplementation of a concentrate with a high (10%) "00" rapeseed meal content aimed at increasing the concentrations of both energy and protein (group 3), had no significant effect on improvement in the fatty acid profile, i.e. changes towards increasing unsaturation of milk fat. dairy cows; CaFA salts; milk; composition; yield 10.17221/3929-CJAS https://cjas.agriculturejournals.cz/artkey/cjs-200605-0003.php https://cjas.agriculturejournals.cz/artkey/cjs-200605-0003.php continuing 51 5 196 204 2006 12121819 periodical academic journal