Isolation Of Solid State Fermentation Strain Of Rapeseed Cake And Application Of Fermented Product In Pig Diets

Microbial fermentation could improve efficiency of feed,which was one of the effective ways improving forage quality of high-quality protein.There were many researches about forage quality improvement of rapeseed meal.However,researches on rapeseed cake were less.Therefore,the paper was aimed to screen out high efficient strains of degradation glucosinolates from soil,and then forage quality of rapeseed cake was improved by fermentation.Furthermore,nutritional value of fermentation production and the optimal dosage in pig diets were explored by metabolic and feeding trials.1.Isolation and identification of bacteria of degrading glucosinolate and optimization of culture conditions.The surface(1-3cm)and depth(3-6cm)soil from rapeseed cake factory was mainly resource for isolating bacteria.Medium of YPD and MRS were employed to purify.Strains of Y4 and R1 were obtained by aerobic and anaerobic conditions’ screening.The taxonomic status of strains was determined by16 S rRNA gene sequence.Medium carbon and nitrogen sources and culture conditions of Y4 and R1 were optimized by single factor and orthogonal design.The results indicated that the kinship of the strains of Y4 and R1 were Bacillus cereus and Lactobacillus plantarum,respectively.Optimal culture conditions of Y4 was as follows: initial pH value was 7.0,the culture temperature was 37 ℃,the culture time was 24 h,the oscillation frequency was 150 r/min;Optimal culture conditions of R1 was as follows: initial pH value was 6.5,the culture temperature was 35 ℃,the culture time was 32 h.2.Optimization of fermentation conditions of rapeseed cake.Fermented conditions of rapeseed cake were optimized on inoculum of Y4 and R1,ratio of material-water(w/v)and the mass ratio of bran and rapeseed cake by single factor and orthogonal design.The results indicated that the optimal combinations of fermentation for mixed strains was as follows: inoculum size of Y4,R1 was 10% and9%,respectively.material-water ratio was 1:1,the mass ratio of bran and rapeseed cake was 1:10(DM),fermentation temperature was 30 ℃,fermentation duration was72 h.The detoxification efficiency of multiple strains was superior to single strain.The degradation rates of glucosinolates,isothio-cyanates(ITC)and oxazolidine-thione(OZT)were 67.26%,60.38% and 53.24%,respectively.The content of crude protein and peptide increased by 2.74 and 2.4 percentage points.The glucosinolates and other anti-nutritional factors of rapeseed cake could effectively degrade,the forage qualitycould efficiently improve by Y4 and R1 mixed solid-state fermentation.3.Evaluation nutrient value of fermented rapeseed cake.A total of 3 healthy crossbred(Duroc × Landrace× Large White)barrows with an initial body weight of75±1.34 kg.Using corn starch-semi-purified protein feed diets,rapeseed cake,fermented rapeseed cake and casein was as the sole protein source.The loss of endogenous nitrogen was measured by casein group.0.3 % of Cr2O3 was as the exogenous indicator.Nutritional value of rapeseed cake before and after fermentation were assessed.The results showed digestible energy(DE)and metabolizable energy(ME)of fermented rapeseed cake were 12.11 and 10.99 MJ/kg,respectively,which were significantly higher than rapeseed cake(P<0.05).Compared with rapeseed cake,the apparent digestibility of DM and CP of fermented rapeseed cake were increased by 7.67% and 13.66%,respectively The apparent ileal(true)digestibility of CP was79.38 %(86.67 %),and they were significantly higher than rapeseed cake(P<0.05).In addition to,valine(Val),phenylalanine(Phe),arginine(Arg)and cystine(Cys),and the apparent and true digestibility of essential amino acids and non-essential amino acids of fermented rapeseed cake were significantly higher than that of rapeseed cake.In conclusion,mixed bacteria solid-state fermentation could effectively improve forage quality,and enhence digestion and utilization of nutrients of rapeseed cake.4.Application of fermented rapeseed cake in growing-finishing pigs diets.A total of 48 healthy crossbred pigs(Duroc×Landrace×Large White,48±2.32kg),were divided into 3 groups,each group with 16,each pen for 8(3 male 5 female).These pigs were feed by automatic feeding system.Experimental diets were used fermented rapeseed cake to replace the soybean meal with the same content of energy and protein.The trial period was divided into the growth phase(48~65kg)and finishing phase(66~90kg).In the growth phase,fermented rapeseed cake replaced soybean meal at30% for Experimental group 1.and at 60% for experimental group 2.In the finishing phase,fermented rapeseed cake replaced soybean meal at 50% for Experimental group 1.and at 100% for experimental group 2.Serum biochemical parameters and intestinal flora were detected in two phases,respectively.Fermented rapeseed cake replacing 30% soybean meal in growth phase and fermented rapeseed cake replacing50% soybean meal in finishing phase had no adverse effects on the growth performance of pig,and improved the metabolism of protein and carbohydrate,composition of E.coli and Lactobacillus,promoted the body’s growth and development.Mixed strains solid-state fermentation of rapeseed cake could improvethe forage quality of rapeseed cake,increase the added proportion of rapeseed cake in animal diets.