EFFECTS OF THERMAL-PROCESSING ON DIGESTIBILITY AND PROTEIN-UTILIZATION OF RAPESEED MEAL OF MEDIUM AND LOW GLUCOSINOLATE TYPE IN DIETS FOR GROWING PIGS

The nutritive value of rapeseed meals (RSM) from Brassica campestris, 0 and 00-cultivars, with medium (25-55-mu-g/g defatted meal) and low ( < 25-mu-g/g) level of glucosinolates (GL), normal solvent extracted me al or thermal treated in order to decrease protein ruminal degradabili ty (Opex-process) or followed also by treating for GL-reduction, was i nvestigated in three digestibility and balance trials with growing pig s. The GL-reduction treatment used removed 0.68 of the original GL, wh ile Opex treated RSM's had 0.33 to 0.45 lower total GL-content than un treated RSM's. The various cultivars or differently processed RSM's we re close to each other in their proximate composition. However, therma l treated 0-RSM had a slightly reduced lysine content compared to untr eated meal. The efficient degradability of dry matter in the untreated RSM's was on average 0.532 and that of the Opex-treated 0.485. The di gestibility of CP in different RSM's varied from 0.677 to 0.842 with n o significant difference between 0 and 00-RSM's or to the RSM treated for GL-reduction (P > 0.05), although 00-RSM's tended to have higher O M and CP digestibilities compared with 0-RSM; pooled mean values being 0.638 vs. 0.715 for OM and 0.715 vs. 0.775 for CP. RSM treated for ru minant escape protein had the same or better digestibility than untrea ted RSM; pooled average values being 0.669 vs. 0.680 for OM and 0.746 vs. 0.757 for CP. This observation has practical importance since the same treatments of RSM could be employed for meals to be used in diets of both ruminants and pigs. In these experiments, the protein utiliza tion was efficient and differences between the dietary treatments were small and insignificant. Heat treatment (Opex) did not decrease prote in utilization despite a small reduction in lysine content.