The study aimed to determine the overall effect of replacing soybean meal completely with soybean expeller cake or extruded full-fat soybean in feed rations for broiler chickens on their carcass composition and meat quality. The experiment involved one hundred and twenty Ross 308 broiler chickens randomly allocated to three equinumerous groups (SBM, SEC, EFS). Each group was divided into five subgroups-each consisting of eight birds of both sexes (1:1). From Day 1 to Day 21 of life the birds were fed with loose starter rations, and from Day 22 to Day 42 they were fed grower rations based on a wheat meal, protein products and mineral and vitamin admixtures. The experimental factor was a protein raw material comprising: SBM group-soybean meal from GM (genetically modified) seeds, SEC-soybean expeller cake from n-GM seeds, and EFS-extruded full-fat soybean from n-GM seeds. The experimental diets were isocaloric and isonitrogenous. It was demonstrated that replacing soybean meal with SEC or EFS in feed rations for broiler chickens led to a significant (p < 0.05) weight gain on Day 42 of rearing by 4.57% and 2.88%, respectively. The chickens fed diets with EFS had worse (more than 4.14%) feed conversion rate (FCR) in comparison to the others (p < 0.05). Broiler chickens from the SBM and SEC groups showed a higher share of breast and leg muscles (by 4.74% and 7.54%) and a lower share of abdominal fat (by 31.1%) and skin with subcutaneous fat (by 18.8% and 13.4%) in comparison with birds from the EFS group (p < 0.05). The highest content of intramuscular fat with the best fatty acids profile was determined in the muscles of birds fed with diets containing EFS, while the muscles of chickens receiving SEC scored the highest. The results provide grounds for recommending SEC in broiler chicken nutrition as it allowed for obtaining the best production and slaughter results, whereas-from the point of view of the human diet-EFS should be recommended since it best modified the lipid fraction of muscles.
Keywords: broiler chicken; extruded full-fat soybean; nutrition; soybean expeller cake; soybean meal.