During the last few years, animal nutrition has been confronted with genetically modified organisms (GMO), and their significance will increase in the future. The study presents investigations on the substantial equivalence of the transgenic Bt (Bacillus thuringiensis) corn and the corresponding nontransgenic hybrid Cesar and parameters of nutrition physiology such as digestibility and energy content for poultry, pigs and ruminants. The results of the analysed corn samples as well as of the silage samples illustrated substantial equivalence in all investigated ingredients, such as crude nutrients, amino acids, fatty acids, minerals and non-starch polysaccharides. The results of the experiments using poultry, pigs, wethers and fattening bulls were not influenced by the genetic modification of corn. The determined values for the digestibilities and the energy contents for poultry, pigs and wethers were not affected by the used corn variety. Neither the examined parameters of the fattening experiments with bulls nor the slaughter results showed any significant differences between the bulls fed on silages made from the nontransgenic or transgenic corn.

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The main sources of variation in body and body gain composition of cattle -body weight, breed, sex, growth rate -are analysed in relation with the net requirements for growth.There is a close relationship between proteins and fat free mass. Therefore, the variations in lipids will be emphasised.

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To analyse substantial equivalence of genetically modified sugar-beets and maize, in which the glufosinate-tolerant (Pat) gene is inserted, crude nutrients, the amino acid and the fatty acid profiles as well as the composition of the NDF-fraction of maize grains were determined and compared with those of the corresponding non-transgenic cultivars. Due to the genetic manipulation differences in crude nutrient contents including sugar and starch were not detected. The amino acid profile of maize grains was analysed to be the same. Fatty acid profile and composition of cell wall constituents did not show any influences as well. Digestibility of Pat-sugar-beets and maize grains for pigs did not demonstrate meaningful differences as compared to the corresponding non-transgenic cultivars. Digestibility of sugar-beet roots and sugar-beet top silage for ruminants proved to be also in the scope of natural variance. As the digestibility of the macro nutrients remained unaffected, the Pat-gene introduction into both crops did not show an influence on the energetic feeding value. For pigs the ME-content of Pat-sugar-beets was determined to be 14.1 MJ/kg DM versus 13.7 MJ of the non-transgenic cultivars. ME-content of Pat-maize grains was 16.0 MJ/kg DM versus 15.8 MJ for controls. For ruminants the feeding value of Pat-sugar-beets was found to be 8.5 MJ NEL/kg DM or 13.2 MJ ME/kg DM, regardless of whether the Pat-gene was inserted or not. The corresponding energy values of sugar-beet top silage ranged between 5.2 and 5.5 MJ NEL/kg DM or 8.6 and 9.1 MJ ME/kg DM, with differences considered in the biological range.