The nutritive value of evening primrose (Oenothera paradoxa) oil cake was estimated from chemical composition and nutrient digestibility. The cake contained on average (per kg): 210 g crude protein, 0.55 UFL, 0.44 UFV, 110 PDI (PDIE -PDIN = -22 g), 92 g PDIA and 100 g of ether extract. The proportion of methionine and cystine in cake was relatively high (1.97 and 2.17 g/16 g N) but that of lysine was rather low (2.00 g/16 g N). Linoleic (C 18 . 2n6 ) -73.1%, y-linolenic (C 18 . 3n6 ) -9,0% and oleic (C 181 n9 ) -6.4% acids dominated in total fatty acid content. Rumen degradability and intestinal digestion coefficients of protein of evening primrose oil cake or seeds were 0.39 and 0.65, respectively.

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The experiment was carried out on 44 Black-and-White Lowland bulls divided into 4 groups and fattened from 155 to 540 kg body weight to investigate the effect of feeding rapeseed oil cake or linseed on bull performance and meat quality. The animals were fed ad libitum a basic complete feed and barley straw (control group) or with similar amounts of supplement fat as linseed, rapeseed oil cake, or rape seed oil. At the end of the experiment 6 animals of each group were slaugh-

The effect of adding evening primrose oil cake or ground full fat rape seed supplements to the diet on animal performance, hormone and metabolite levels in blood plasma, and milk fatty acid composition was compared in an experiment on 21 Black-and-White Lowland cows divided into 3 groups of 7. The animals were fed control basic diet (group C) or diets supplemented with evening primrose cake (group P) or full fat rape seeds (group R). Daily milk production in cows of group P was 0.9, and of group R 1.8 kg (FCM) higher than in cows of the control group. The milk fat contents were 3.99, 4.02 and 3.97%, and protein contents 2.98, 2.93 and 2.81% in groups C, R and P, respectively. The plasma cholesterol level was 20% lower in group C and 26% lower in group P than in group R. The content of C18-acids, including polyunsaturated acids, in the milk fat of cows of group P and R was similar and higher than in controls.

An experiment was carried out on 44 Black-and-White Lowland bulls allocated to 4 groups and fattened from 184 to 530 kg average body weight to investigate animal performance and meat quality when fed diets with balanced energy:protein ratio according to the INRA system. Diets consisted of maize silage and concentrate for the control group, supplemented with linseed, rapeseed oil cake, rape seed oil as additional fat sources for the experimental groups. Six animals from each group were slaughtered at the end of the experiment. The physical and chemical properties of meat, and its individual fatty acid and cholesterol contents were estimated. Average body weight gains of animals were similar in all groups reaching about 1.35 kg day 1. The fat content increased to about 5% in dry matter with about 50% fat from linseed or rapeseed oil cake, enriched the lipids of M. longissimus dorsi in essential and unsaturated fatty acids, conjugated linoleic acid and decreased the cholesterol level, which was particularly marked when feeding the diet supplemented with rapeseed oil cake. The highest ratio of hypocholesterolemic to hypercholesterolemic acids was also found in the meat of animals fed diet with rapeseed oil cake.