Study On Palm Kernel Cake Fermented With Bacteria And Enzyme And Its Mechanism On Improving Growth Performance Of Broilers

Palm kernel cake（PKC）represents high social and economic value as animal feed due to its low price,but high crude fiber content prevents its extensive usage in animal diet.In this paper,we studied the optimum condition for PKC fermenting with bacteria and enzyme,evaluated the effects of PKC fermented with bacteria and enzyme（FEPKC）on performance,serum biochemical indexes and cecal microbiota diversity of broilers,and investigated the optimal addition proportion of FEPKC in broiler diet and the mechanism of FEPKC improving the performance of broilers.The results of seven experiments are as follows:Exp.1.The aim of this experiment was to screen the suitable strains for the treatment of PKC.10strains of lactic acid bacteria,8 strains of yeast and 12 strains of bacillus stored in our laboratory were taken as starting strains.Through MRS-calcium carbonate plate method and Oxford cup method,the strongest lactic acid bacteria strains which produce acid and inhibit Escherichia coli and Salmonella were screened.The most suitable yeast strain was screened by measuring the biomass generation of liquid medium of PKC.The Bacillus strains with the strongest fiber and protein degradation were screened by sodium carboxymethyl cellulose plate method and casein plate method.The required microbial strains were Lactobacillus plantarum D,Saccharomyces cerevisiae Y1 and Bacillus subtilis B2.Exp.2.PKC was fermented by L.plantarum D,S.cerevisiae Y1 and B.subtilis B2,with single strain,mixed by two strains and mixed by three strains,respectively.The solid-water ratio of the fermentation system was 1:1,inoculation amount was 10%,and fermentation time was 5 d.The fermentation temperatures of L.plantarum D,B.subtilis B2 and S.ceravisiae Y1 were 37℃,37℃and30℃,respectively,and the fermentation temperature of all mixed bacteria was 30℃.A L₁₆（4⁵）orthogonal experiment was designed.Temperature,solid-water ratio and inoculation amount were taken as experimental factors,and p H value,reducing sugar and neutral detergent fiber（NDF）content were taken as evaluation indexes.The optimum condition for PKC fermentation were 30℃,solid-water ratio1:1 and inoculation amount of 10%.Exp.3.50 g PKC in 500 m L triangle and inoculated with fermentation broth of 10%L.plantarum D and S.cerevisiae Y1 at a solid-water ratio of 1:1.The levels of mannanase,cellulase andα-galactosidase were added at 0.05 g,0.1 g,0.5 g,1.0 g and 1.5 g,respectively.The mixture was cultured at 30℃for 5 d.A L₉（3⁴）orthogonal experiment was designed by choosing three optimal gradients of the 3 enzymes.Under the optimal production conditions,the crude protein of FEPKC was increased by 15.10%from 16.03%to 18.45%,crude fiber and NDF contents decreased by 25.10%and21.96%,respectively.Exp.4.Seventy-two 21-day-old healthy AA broilers with similar body weight were randomly divided into 3 groups with 6 replicates per group and 4 broilers per replicate.Substitution method and indicator method were used to study the effects of FEPKC on apparent metabolizable energy（AME）of broilers.The results showed that,the AME of PKC and FEPKC were 6.33 MJ/kg DM and 8.47 MJ/kg DM,respectively.Exp.5.108 healthy AA broilers with similar body weight were selected and randomly divided into3 groups with 6 replicates per group and 6 broilers per replicate.The apparent ileal amino acid digestibility（AID）of FEPKC was studied by nitrogen-free diet method and indicator method.The results showed that AID of lysine was significantly decreased;AID of proline and histidine tended to increase;but the difference was not significant,AID of other amino acids was significantly increased.Exp.6.A total of 420 day-old AA broilers were randomly divided into 7 groups with 6 replicates per group and 10 broilers per replicate.Groups were fed corn-soybean meal basal diet,and experimental diets supplemented with 4%,8%and 12%PKC and FEPKC,respectively.Compared with the control group,the growth performance of broilers was improved by FEPKC,while inhibited by PKC.12%FEPKC group improved the performance of broilers most obviously.Compared with the control group,the FEPKC had no significant effects on the slaughter performance,immune organ index,and serum antioxidant capacity of broilers.The FEPKC did not affect the lipid metabolism,but improved the protein metabolism of broilers.Exp.7.The addition of PKC and FEPKC significantly changed theβ-diversity of cecal microbiota of broilers.The relative abundance of Firmicutes in FEPKC group was significantly lower than control and PKC group,and the relative abundance of Proteobacteria was significantly higher than control and PKC group.At genus level,the relative abundance of Alistipes in FEPKC group was significantly higher than control and PKC group.Through LEfSe analysis,the main biomarkers of PKC group were Anaerostipes and Clostridium,and the main biomarkers of FEPKC group were Bacteroidetes and Alistipes.In conclusion,this study utilized L.plantarum D and S.cerevisae Y1,combined with mannanase,cellulase andα-galactosidase to ferment PKC to obtain nutritional value significantly improved FEPKC.FEPKC improved the growth performance of broilers by affecting the related indexes of serum protein metabolism and the structure of cecal microbiota.