Study On Solid State Fermentation Conditions Of Corn Gluten Meal And Its Feeding Effect On Dairy Cows

At present,the development of dairy industry in China is facing many challenges,the most prominent of which is the shortage of feed resources,especially the shortage of high-quality protein feed resources based on soybean meal,so it is urgent to develop a new type of high-quality protein feed.Corn gluten meal(CGM),a by-product of corn starch processing,has an extremely abundant output and is often used as animal feed to meet the protein needs of animals.However,the low digestibility and unbalanced amino acid composition of CGM limit ed its application in animal feed,which needs further developmen t.Solid state fermentation technology can improve the quality of protein in feed,thereby increasing the utilization rate of protein.Therefore,in order to overcome the key problem of the shortage of high-quality protein feed resources in China,the present research started from the perspective of developing a new type of high-quality fermented protein feed,the fermentation conditions of CGM fermented by lactic acid bacteria and acid protease were first optimized by response surface analysis,and the feeding effect of fermented corn gluten meal(FCGM)on weaned calves and lactating cows was further evaluated,which is of great significance to improve the utilization of plant protein resources and promote the development of animal husbandry in China.Experiment 1:Screening of CGM solid state fermentation conditionsTaking the corn peptide yield as the target value,the effects of different levels of wheat bran and CGM ratio,lactic acid bacteria inoculation amount,acid protease addition amount,fermentation time,fermentation temperature,moisture content and initial p H on the target value were studied by single factor experiment,so as to determine the optimal level range of each factor;Then,Plackett Burman experimental design was used to determine the primary and secondary effects of the above seven variables on the target value at two levels,which found that the significant(P<0.05)influencing factors were the inoculation amount of lactic acid bacteria,the addition amount of acid protease and moistu re;Finally,the Box and Behnken experimental design in response surface analysis was used to analyze the interaction effects between the significant factors at 3 levels,and the optimal fermentation conditions for CGM obtained through statistical analysis were as follows:enzyme amount=0.54%,bacteria amount=5.6×10⁹ cfu/g,moisture=46%,temperature=36°C,bran flour ratio=4:6,time=120 h,and natural p H.The predicted value of corn peptide yield was 37.35%(%protein).According to the optimal fermentation conditions,CGM was refermented three times,and the yield of corn peptide was 35.97%,36.83%and 37.96%,which was close to the predicted value.Experiment 2:Analysis of the changes of CGM components before and after fermentationAccording to the optimal fermentation conditions obtained in the above part,CGM was fermented again,and the changes of nutritional parameters,fermentation parameters,protein secondary structure and antioxidant capacity in vitro before and after CGM fermentation were studied.The results showed that the contents of crude protein,ether extract,reducing sugar,total phenol and lactic acid in CGM increased significantly after fermentation,wh ereas the contents of neutral detergent fiber,acid detergent fiber,starch,ash,total sugar and p H decreased significantly(P<0.05).The results of polyacrylamide gel electrophoresis showed that the molecular weight of CGM protein was mainly distributed between 10 k Da and 55 k Da,while the molecular weight of FCGM protein was mainly below 15 k Da,indicating that the macromolecular protein in CGM was hydrolyzed to small molecule protein after fermentation.The results of fourier transform infrared spectroscopy showed that the peak area of amide I and the peak height of amide II in CGM increased significantly after fermentation,while the ratio of?-helix to?-fold peak height decreased significantly(P<0.05).In addition,the scavenging capacity of 1,1-diphenyl-2-picrylhydrazyl,hydroxyl radical,superoxide anion radical and Fe³⁺reducing capacity of CGM were significantly increased by fermentation(P<0.05),indicating that CGM after fermentation had higher antioxidant capacity in vitro,so its biological activity was stronger.Experiment 3:Study on the effect of FCGM on calves after weaningTwenty-four healthy Holstein calves with similar body weight(mean±standard deviation;83.36±5.96 kg)and age(56.21±4.26 d)were enrolled in a randomized complete block design were blocked for body weight and age before being randomly assigned to 1 of 2 treatment groups:(1)untreated basal diet group(control group);and(2)diet supplemented with 5%FCGM treatment group(experimental group)throughout the 8 weeks feeding trial.Feed intake,body weight,withers height,heart girth and body length were recorded and the blood and rumen fluid samples were collected and the related indices were analyzed.The results showed that the average daily gain and feed efficiency of the calves fed FCGM were significantly higher than those of the control group(P<0.05).Compared with the control group,the contents of plasma total protein,glucose,total superoxide dismutase,catalase,total antioxidant capacity,immunoglobulin A,immunoglobulin G,insulin like growth factor-I and growth hormone in the trial group were significantly increased(P<0.05).After feeding FCGM,calves'ruminal ammonia nitrogen,total volatile fatty acids,acetic acid,pr opionic acid,microbial protein concentration and protease activity increased significantly,but ruminal p H value decreased significantly(P<0.05).Furthermore,the relative abundances of Bacteroidetes,Prevotellaceae,Prevotella?1 and Prevotellaceae?UCG-003 of the calves fed FCGM increased significantly,while the relative abundances of Firmicutes,Proteobacteria,Bacteroidales?S24-7?group and Ruminobacter decreased significantly(P<0.05),which indicated that FCGM feeding could change the composition and structure of rumen bacterial community in calves.Experiment 4:Study on the effect of FCGM feeding dairy cows in lactation periodNine healthy multiparous(parity=3)Holstein cows with similar body weight(624±14.4 kg),days in milk(112±4.2)and milk yield(31.8±1.73 kg,all mean±standard deviation)were enrolled in a replicated 3×3 Latin square design with three 28-d periods.Cows were fed one of three dietary treatments in which FCGM replaced some portion of soybean meal in the diets as follows:(1)unreplaced basal diet(0FCGM),(2)50%replacement of soybean meal with FCGM(50%FCGM),and(3)100%replacement of soybean meal with FCGM(100%FCGM).The daily milk yield and feed intake were recorded,and the blood,rumen fluid,feces and milk sam ples were collected and the related indices were analyzed.The results showed that cows fed different levels of FCGM significantly increased the yields of milk,lactose and milk protein and the concentrations of lactose and milk protein compared with the 0FCGM group,and they all increased linearly with the increase in FCGM feeding amount(P<0.05).Compared with 0FCGM group,the dry matter and crude protein digestibility of 50%FCGM group and 100%FCGM group tended to increase,and showed a linear increasing effect with the increase of FCGM feeding amount(P<0.05).After feeding different levels of FCGM,the plasma glucose and immunoglobulin G concentration of dairy cows increased linearly,the ruminal total volatile fatty acids,propionic acid concentration and microbial protein production increased linearly,while the plasma malondialdehyde concentration and rumen p H value decreased linearly(P<0.05).Compared with the 0FCGM group,the relative abundances of rumen bacterial Prevotellaceae,Veillonellaceae,Saccharimonadaceae,Prevotella?1,Selenomonas?1 and Candidatus?Saccharimonas of the dairy cows in the 50%FCGM group and 100%FCGM group increased significantly,and they showed a linear increasing effect with the increase of FCGM feeding amount(P<0.05).On the contrary,the relative abundances of rumen bacterial Succinivibrionaceae,Muribaculaceae,Succinivibrionaceae?UCG-001 and Prevotella?7 of cows fed different levels of FCGM decreased significantly(P<0.05).In summary,this study drew the following conclusions:(1)The optimum technological parameters of CGM solid state fermentation were as follows:enzyme dosage=0.54%,inoculum size=5.6×10⁹ cfu/g,mositure=46%,fermentation temperature=36°C,wheat bran:CGM=4:6,fermentation time=120 h,natural p H,which provided data reference for processing FCGM in the market.(2)The nutritional value of CGM can be improved by co-fermentation of lactic acid bacteria and acid protease.(3)FCGM can be used as a substitute for soybean meal to improve the production performance of calves and lactating cows,improve their rumen fermentation pattern and the composition of rumen bacterial community,indicating that it is feasible for FCGM to be used as a substitute for soybean meal in the production of dairy cows.