Spontaneous and enzymatic fermentation of rapeseed cake for broiler nutrition

The present study evaluated effects of fermentation with or without enzymes (phytase, pectinase and β-glucanase) on the nutritional quality of rapeseed cake (RSC). The impact on growth performance and nutrient digestibility in broilers as a consequence of substituting soybean meal (SBM) in the diet with fermented RSC was also investigated. A standard maize-wheat-SBM diet was used as the control (CON). Second experimental diet was produced using untreated RSC (NR; 150 g/kg) as a substitute for SBM. Third and fourth diets were produced using RSC that had been fermented either without (SFR; 321.8 g/kg) or with (EFR; 312.8 g/kg) enzymes. For these two diets, the same diet formulations as NR diets were used. However, since DM content of the fermented products was considerably lower than untreated RSC (355 and 345 vs. 928 g/kg), the inclusion rate of the fermented products in the EFR and SFR diets were adjusted to have the same amount of rapeseed cake DM in the SFR and EFR diets as it was included in the NR diets. A fifth diet (NRE) was produced using 150 g/kg untreated RSC and in-feed inclusion of the same enzymes (at the same inclusion level) as present in the EFR diet. Performance variables were recorded and the coefficient of apparent ileal digestibility (CAID) of crude protein, fat, amino acids, Ca and P was determined at the end of the trial (d 35). Data were subjected to ANOVA using the GLM procedure. Fermentation of RSC with enzymes effectively reduced its phytate and insoluble-NSP content, but in the absence of enzymes, fermentation had only a moderate effect on reducing insoluble-NSP concentration. The dietary treatments had no impact on body weight gain or feed intake in this study (P > 0.05). At the end of the starter period (d 1–21) and entire experiment (d 1–35), feed conversion ratio (FCR) in broilers fed the NRE diet was lower compared with those receiving the CON or NR diet (P ≤ 0.05). At d 1–21, broilers in the EFR treatment group displayed lower FCR than those in the CON or NR group, but at d 35, birds fed the EFR diet showed lower FCR compared with those fed the NR diet (P ≤ 0.05). The experimental diets had no impact on CAID of crude protein, fat and all of the amino acids, except cysteine and glycine (P > 0.05). Birds receiving the EFR and NRE diets showed higher CAID of P compared with those fed the CON, NR or SFR diet. Birds in the NRE group showed higher CAID of Ca compared with those in the NR or SFR group, with those in the NR group presenting the lowest CAID of Ca (P ≤ 0.05). In conclusion, enzymatic fermentation of RSC effectively reduced its anti-nutrient content. Partial replacement of SBM with RSC in broiler diets had no negative impact on digestibility of the nutrients and growth performance of broilers. Furthermore, inclusion of enzymatically fermented RSC in broiler diets and supplementation of the diets containing untreated RSC with a mixture of phytase, pectinases and β-glucanase could improve the CAID of some of the nutrients and led to better feed efficiency for these diets.