Effects Of Low Soybean Meal Diet On Growth Performance,Intestinal Health And Liver Metabolism Of Growing-finishing Pigs

In recent years,The Ministry of Agriculture and Rural Affairs has vigorously promoted the action of reducing and replacing corn and soybean meal,actively opened up new resources for protein feed,and reduced its dependence on imported feed and grain by "improving efficiency,open source and adjusting structure" to ensure national food security.The aim of this study was to reduce protein level and further replace soybean meal with miscellaneous meal to construct low-soybean meal diet,and to study its effects on performance,intestinal health and liver metabolism of growing-finishing pigs,in order to reduce the dependence of pig feed on soybean meal,and to provide theoretical basis for solving the shortage of protein resources in breeding industry.Experiment 1: Effect of low soybean meal diet on production performance and blood biochemical indexes of growing-finishing pigsA total of 80 Landrace × Yorkshire pigs with body weight of 19.97±0.27 kg was randomly divided into 4 treatments,5 replicates per treatment,4 pigs per replicate(2 male and female).The experiment was divided into three body weight stages(20-50 kg,50-80 kg and 80-110 kg),feeding for 46 days,30 days and 21 days,respectively.The four treatments were control group(CON): corn-soybean meal basal diet;Low protein group(LP): low soybean meal diets with protein levels reduced by 1.5%,1.4%,and 1.1% at three body weight stages,respectively;5.1% mixed meal group(CMM1): The low soybean meal diet of LP group was replaced by mixed meal(cottonseed meal: corn germ meal: corn protein meal = 1:1:1,1.7% each)with about 5% soybean meal;10.2% mixed meal group(CMM2):The low soybean meal diet of LP group was replaced by mixed meal(cottonseed meal: corn germ meal: corn gluten meal = 1:1:1,3.4% each)with about 10% of soybean meal.The levels of dietary protein in CMM1 and CMM2 groups were similar to those in LP group.Daily feed consumption and body weight at the beginning and end of each stage were recorded during the experiment.Blood samples were collected four days before the end of the experiment.Five pigs in each group were randomly selected for slaughter to determine slaughter performance and meat quality after fasting for 12 h at the end of experiment.The results showed as follows: In the 20-50 kg stage,the average daily feed intake(ADFI)decreased significantly(P < 0.05)and average daily gain(ADG)(P < 0.01)compared with CON and LP groups.With the increase of mixed meal replacement amount,ADFI decreased linearly(P < 0.01),and the feed: gain ratio(F/G)showed quadratic effect(P<0.05,first increased and then decreased).There was no significant difference in ADG,ADFI and F/G in each treatment group at 50-110 kg(P>0.05).In the whole period,each treatment had no significant effect on ADFI and F/G of the growth-finishing pigs(P>0.05),but compared with the CON and LP groups,ADG of CMM1 group had a tendency to increase(P=0.059),and ADG of CMM2 group had a tendency to decrease(P=0.059).;with the increase of mixed meal replacement amount,the whole period ADFI decreased linearly(P<0.01),and ADG showed quadratic effect(P<0.05,first increased and then decreased).The carcass skew length of growing-finishing pigs first increased and then decreased with the increase of mixed meal replacement amount(P<0.05),but there were no significant differences in slaughter performance such as live weight before slaughter,carcass weight,slaughter percentage,back fat thickness,ocular muscle area,carcass straight length,meat color,p H value and meat quality among all treatment groups(P>0.05).Compared with CON group,serum inorganic phosphorus content in LP group was significantly increased(P<0.05),the contents of serum inorganic phosphorus and total cholesterol decreased linearly with the increase of mixed meal replacement amount(P<0.05),there were no significant differences in other serum biochemical indexes among treatment groups(P>0.05).Experiment 2: Effect of low soybean meal diet on intestinal health of growing-finishing pigsThe enzymatic hydrolysis and fermentation products formed when dietary protein passes through the digestive tract can affect the intestinal function and health of pigs.This study comprehensively investigated the effects of low-soybean meal diet on intestinal health of growing-finishing pigs from the aspects of intestinal morphology,intestinal barrier,intestinal microflora and its metabolites.The design of the experiment was the same as that of experiment 1.Intestinal contents and tissue samples were collected after slaughter.The results showed that there were no significant differences in m RNA expression of intestinal morphology,Intestinal microbial diversity and its metabolites,expression of mucin-2(MUC-2),interleukin-1β(IL-1β),interleukin-6(IL-6),tumor necrosis factor-α(TNF-α),transforming growth factor-β(TGF-β),and Occludin genes in the jejunum(P > 0.05).However,when compared with the CON group,The m RNA expression of Claudin-1significantly increased in the LP group(P < 0.05),The m RNA expression of interleukin-10(IL-10)was usually increased(P = 0.096),The m RNA expression of ZO-1 and Claudin-1 in the jejunum was increased significantly in the CMM2 group(P < 0.05);With the increase of mixed meal replacement amount,the m RNA expression of MUC-2 decreased(P = 0.073),Significant linear increase in m RNA expression of ZO-1(P < 0.05),The m RNA expression of IL-10 was very significantly linear reduced(P < 0.01).Experiment 3: Effect of low soybean meal diet on liver metabolism of growing-finishing pigsAccording to the previous two experiments,low soybean meal diet can affect the growth performance and m RNA expression levels of IL-10 in jejunum of growing-finishing pigs.The growth performance of animals depends on the metabolism of the body,and the liver is a very important metabolic center and the place of various metabolic reactions in the body of animals,and its metabolic state directly reflects the health of the body.Therefore,in this study,metabolomics technology was used to analyze metabolite spectrum in liver of growing-finishing pigs,and the effects of low soybean meal on liver metabolome of growing-finishing pigs were studied.The results showed that low soybean meal diet had no significant effect on liver metabolites of growing-finishing pigs,but the low soybean meal diet that only reduced the diet protein level could promote body immunity by regulating retinol metabolism,and the low soybean meal diet that replaced some soybean meal could affect the liver metabolic homeostasis through arachidonic acid metabolism and linoleic acid metabolism.In conclusion,low soybean meal diet has no significant effect on slaughter performance,intestinal microbial diversity,metabolites and liver metabolism of growing-finishing pigs,and improved the tight connectivity of jejunum.5.1% mixed meal replacement of soybean meal could also significantly improve the early growth performance of growing-finishing pigs.These findings indicate that it is feasible to feed growing-finishing pigs with low soybean meal diet on the basis of isoenergy and amino acid balance,and provide a theoretical basis for developing a scientific and effective soybean meal reduction alternative.However,attention should be paid to the potential adverse effects of 10.2% mixed meal replacement on early growth performance of pigs due to palatability and other reasons.