The effect of raw and fermented rapeseed cake on the metabolic parameters, immune status, and intestinal morphology of turkeys

This study evaluated the effects of including 15% of raw or fermented rapeseed cake (RRC and FRC, respectively) in turkey diets on the growth performance, antioxidant and immune status, and intestinal morphology of birds. Rapeseed cake was fermented using the commercial 6-phytase enzyme preparation, and dried. A total of 1,350 day-old female Hybrid Converter turkeys were randomly allocated to 3 dietary treatments with 9 replicates per treatment and 50 birds per replicate. All diets were isonitrogenous and isocaloric, and contained various protein sources. In the control group (C), soybean meal was the main source of dietary protein, and the remaining groups were fed diets containing 15% of RRC or FRC. Fermentation considerably reduced the concentrations of phytate-phosphorus and glucosinolates in rapeseed cake. In comparison with RRC, turkeys receiving FRC achieved higher average final body weight (BW), comparable with that noted in the control group. Both RRC and FRC stimulated the antioxidant system of turkeys, which was reflected in a decrease in the concentrations of lipid hydroperoxides (LOOH) and malondialdehyde (MDA), and an increase in the total antioxidant potential (FRAP) and the concentration of total glutathione (GSH GSSG) in blood plasma, compared with the control group. Turkeys fed diets with RRC were characterized by the highest blood vitamin C concentrations, the highest activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx), and lower catalase (CAT) activity. The dietary inclusion of rapeseed cake contributed to an increase in villus height and mucosal thickness in the duodenum, and a more beneficial influence was exerted by RRC. It can be concluded that the fermentation of rapeseed cake considerably reduces the concentrations of glucosinolates and phytate-phosphorus, and increases the final BW of turkeys. Diets containing 15% of RRC and FRC do not compromise metabolic parameters or immune function, and exert positive effects on antioxidant status and intestinal histomorphology in turkeys.