| Abstract: | Two double low rapeseed varieties were separated into small and big seeds to study their nutritive value for broiler chickens. The seed weights for small and big seeds of spring rape variety Jaguar were 3.6 and 4.9 mg, and of winter rape Impala were 4.1 and 5.3 mg, respectively. Analytical results showed no significant differences in protein and fatty acid content between the big and small seeds. The small seeds contained more fibre constituents, eg lignin 13.7% higher for Jaguar and 3.4% higher for Impala, the other dietary fibre components show ed a similar trend. The big seeds, however, tended to be higher in fat and gross energy, but also in total glucosinolates. A 2 × 2 × 3 factorial design was performed on 24 broilers, to investigate the apparent digestibility and growth performance during three successive periods of balance trials, using diets consisting of 350 g kg?1 full-fat rapeseeds and 650 g kg?1 remainder feed mixture identical for all treatments. The diets with big seeds clearly showed higher digestibility for all measured dietary components. The surpluses as absolute percentage units respectively for dry matter were 2.8 (P < 0.001); gross energy 3.8 (P < 0.001); fat 7.9 (P < 0.001) and protein 1.6 (P = 0.045). The same trend was also found in the digestion of fatty acids and vitamin E. The big seeds displayed 7% higher (P = 0.071) growth rate and 8% higher (P = 0.002) feed conversion, respectively. Greater nutritional superiority of the big seeds was observed on the earlier growth ages, indicating the young birds are more sensitive to the seed size difference. It is concluded that the big seeds are more digestible than the small seeds and that a selection towards Digger seed size or a mechanical separation during processing will be beneficial. |
