The effect of hen feather keratin meals as a protein component of the diet for dairy cows on milk yield and composition (Experiment I) and on calf performance (Experiment II) was studied. Experiment I , lasting from calving to day 84 of lactation, was carried out on 48 dairy cows divided into 4 groups fed rations containing only plant-origin feeds with (SM) or without (S) protected methionine supplement or rations containing feather keratin meal with (KM) or without (K) methionine. The proportion of keratin crude protein was about 36%, and rumen undegraded keratin protein about 23% of the total crude protein of the diet. The intake of DM, UFL and average daily milk production for the entire experimental period were similar in all groups, but the intake of crude protein and intestinally digested protein in groups K and KM was higher (P<0.01) than in groups S and SM. However, higher daily milk production was obtained between days 22 to 36 of lactation from cows receiving keratin meal (P<0.05) or methionine (P<0.01) supplements. The lactose concentration in the milk of cows receiving keratin meal in group K was higher (P<0.01) than in the milk of those on soyabean oilmeal protein diet. Methionine supplementation increased the protein and fat contents in milk and this increase was slightly more pronounced in the milk of cows receiving keratin meal. Experiment II , lasting from days 7 to 120 of life, was carried out on 5 groups of 10 calves fed concentrate mixtures containing soyabean oilmeal as the main source of protein in the control group, C; in the experimental groups the oilmeal was substituted with different proportions of protein of keratin meal: 30% - group K₃₀, 60% - group K₆₀, 100% - group K₁₀₀ or with equal amounts of keratin and blood meal - group KB_50/50. In 1 kg all concentrate mixtures contained about 160 g of crude protein, 110 g BTJ and 1 UFL and were fed ad libitum with 0.2 to 0.3 kg/day of meadow hay. No significant effect of keratin meal protein in the diet on daily gains or feed efficiency was found, however, calves in groups C and K₃₀ had a tendency towards higher daily body weight gains than in the other groups.