Study of gamma irradiation effects on chemical composition, anti-nutritional factors, protein degradation kinetics and in vitro protein digestibility of native rapeseed meal and canola meal

In order to evaluate effects of gamma irradiation on ruminal dry matter (DM) and crude protein (CP) degradability، in vitro CP digestibility، anti-nutritional factors and chemical composition of native rapeseed meal (NRM) and canola meal (CM)، present study was carried out. Bags were filled with untreated or irradiated NRM and CM at doses of 15، 30 and 45 kGy، then incubated in the rumen of three ruminally fistulated Taleshi bulls for periods of 0، 2، 4، 8، 16، 24 and 48 h and resulting data were fitted to non linear degradation model to calculate degradation kinetics of DM and CP. Digestibility of rumen undegraded CP was estimated using the three-step in vitro procedure. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) was used to monitor protein subfractions and the fate of true proteins of untreated and gamma irradiated NRM and CM in the rumen. The phytic acid of NRM and CM decreased (P<0. 05) as irradiation doses increased، but irradiation up to 30 kGy decreased (P<0. 05) the total glucosinolate content of NRM and CM. -irradiation had no effect on chemical composition of NRM and CM. The washout fractions and effective degradability of DM and CP decreased (P<0. 05) and potentially degradable fractions of DM and CP of NRM and CM increased (P<0. 05) as irradiation doses increased. Gamma irradiation increased (P<0. 05) in vitro CP digestibility of NRM and CM. Electrophoresis results of NRM and CM revealed that gamma irradiation at doses of 30 and 45 kGy reduced degradability of cruciferin and especially napin subunits in the rumen. In conclusion، gamma irradiation reduced ruminal degradability of protein and anti-nutritional factors of NRM and CM and increased in vitro CP digestibility of them at doses higher than 15 kGy.