| This experiment studies the compound and effect of acidifier through in vitro test and animal feeding test.Ten kinds of single acidifiers are screened through in vitro bacteriostasis test and simulated digestion test,and three kinds of compound acidifiers are composed respectively: digestive,bacteriostatic and comprehensive.Then three kinds of functional compound acidifiers are screened in vitro to determine the optimum proportion and the optimum adding level of each acid in the compound acidifier.And feeding experiments are conducted to determine the effects of three different functional compound acidifiers on growth performance,fecal index and serum biochemical index of piglets,so as to provide reference for the effect and application of compound acidifiers.Test 1: Screening of single acidifier in vitro10 kinds of single acidizing agents(lactic acid,benzoic acid,citric acid,fumaric acid,formic acid,phosphoric acid,sorbic acid,tartrate,malic acids,hydrochloric acid)were used to compare the inhibitory effects of 10 acidizing agents on Escherichia coli by in vitro bacteriostatic tests.The effects of 10 acidizing agents on p H,digestibility of DM and CP,butyric acid content of digestive fluid were determined by simulated digestion test in vitro.The test results show that:(1)The order of bacteriostatic effect of 10 acidifiers is phosphoric acid,citric acid,benzoic acid,lactic acid,fumaric acid,formic acid,malic acid,sorbic acid,tartaric acid and hydrochloric acid.(2)According to the results of simulated digestion test in vitro,the order of digestive effects of 10 acidifiers is lactic acid,fumaric acid,benzoic acid,phosphoric acid,malic acid,sorbic acid,formic acid,tartaric acid and hydrochloric acid.Test 2: Screening of compound acidifiers in vitro.The "uniform design method" is used to design seven different proportions of the bacteriostatic compound acidifier(lactic acid,fumaric acid,benzoic acid,phosphoric acid)consisting of four acidifiers with the best bacteriostatic effect,the digestive acidifier(phosphoric acid,citric acid,benzoic acid,lactic acid)consisting of four acidifiers with the best digestive effect and the combination acidifier(phosphoric acid,citric acid,lactic acid,fumaric acid)with both bacteriostatic and digestive effects.The optimum ratios are screened out by diet p H and diet acid-binding capacity.Then,three kinds of functional compound acidifiers with the best proportion are designed into 0.0%(control group),and three adding levels of 0.1%,0.3%,0.5%.And the optimum adding level of each functional compound acidifier is screened out through in vitro bacteriostasis and in vitro simulated digestion test.The test results show that:The optimum ratio and adding level of three kinds of compound acidifiers are as follows: 0.3% bacteriostatic compound acidifier phosphoric-citric-benzoic-lactic acid(36%,28%,14%,8%),0.5% digestive compound acidifier lactic-fumaric-benzoic-phosphoric acid(36%,28%,14%,8%)and 0.3% comprehensive compound acidifier lactic-phosphoric-fumaric-citric acid(28%,28%,13%,13%).Test 3: Effect of compound acidifier on growth performance,serum biochemical index and fecal index of weaned piglets.A single factor design is used to select 120 healthy "Duroc × Landrace ×White" piglets aged 21 days and weighing about 8 kg.They are randomly divided into four groups with 5 replicates in each group.The first group is the control group and fed with basal diet,the second group is the bacteriostatic group,adding 0.3% bacteriostatic compound acidifier to the basal diet,the third group is the digestive group,adding 0.5% digestive compound acidifier to the basal diet,the fourth group is the comprehensive group,adding 0.3% of the comprehensive compound acidifier to the basal diet.The growth performance,blood biochemical index and fecal index of weaned piglets are measured.The experimental period is 28 days.The test results show that:(6)The production performance of weaned piglets is improved in varying degrees by adding different types of compound acidifiers.Compared with the control group,the digestive group significantly increased the average daily gain of piglets(P<0.05),and decreased feed/weight ratio of weaned piglets(P>0.05).Adding different kinds of compound acidifiers can reduce diarrhea rate of piglets.(7)During whole trial period,compared with the control group,the bacteriostatic group,digestive group and comprehensive group can increase the contents of Ig G,Ig A,Ig M of immunoglobulin,as well as the contents of T4 and IGF-1 in piglets in varying degrees.The effect of comprehensive group is the best.Adding three different kinds of functional compound acidifiers can increase or decrease the T3 content in serum of weaned piglets,but there is no significant effect(P>0.05).(8)During whole trial period,compared with the control group,the bacteriostatic group,digestive group and comprehensive group can increase the total protein and albumin content in varying degrees,and reduce the urea nitrogen and uric acid content.The bacteriostatic group has the best effect on increasing total protein and albumin and reducing uric acid content.The digestive group has the best effect on reducing urea nitrogen content.(9)The bacteriostatic group and the comprehensive group can significantly decrease the fecal p H(P < 0.05)and ammonia content(P<0.05),while the digestive group can significantly decrease the fecal p H(P<0.05).The bacteriostatic group can significantly increase the content of bifidobacterium and lactobacillus and decrease the escherichia coli content(P<0.05).The digestive group and the comprehensive group can significantly increase the lactobacillus content and decrease the escherichia coli content(P<0.05).(10)The utilization rate of dry matter and crude protein is significantly increase in digestive and comprehensive groups(P<0.05).In summary,all three kinds of compound acidifiers can affect the production performance,blood biochemical index and fecal index of piglets in varying degrees.The effect of 0.5% digestive compound acidifier is better,followed by 0.3% comprehensive acidifier. |
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