| Fly maggot is animal protein resource rich in fatty acids,proteins,vitamins and other nutrients and bioactive substances.On March 15,2021,the Ministry of agriculture and rural areas proposed 《Alternative work plan for reduction of corn soybean meal in feed》and comprehensively banned the addition of antibiotics in feed from July 1,2020.It made the animal husbandry industry faces the problems of reducing the growth performance of livestock and poultry and increasing the death and culling rate.Therefore,it is essential to use new protein derived feed substitutes to regulate these diseases caused by oxidative stress.In this paper,the homogenate of fly maggot larvae was hydrolyzed by enzymatic hydrolysis,and the antioxidant and stability of its products were studied.Then,the SPF chick inflammation model constructed in this experiment was used as the experimental animal to study the effects of adding different levels of fly maggot antioxidant peptides on its growth performance,serum antioxidant,digestive function and other indicators.The main research contents and results are as follows:Experiment 1: preparation and stability of antioxidant peptide from fly maggotIn this experiment,the homogenate of fly maggot larvae was used as the substrate for enzymatic hydrolysis with proteases from different sources(pepsin,trypsin,neutral protease and papain)and double combination enzymes.The degree of hydrolysis,polypeptide concentration,DPPH free radical scavenging ability and other indicators of the hydrolysates between the treatment groups were measured.The suitable enzymolysis products were selected from different treatment groups,and the antioxidant activity and stability were analyzed.The results showed that the fly maggot oxidized peptide lyophilized powder with light yellow and good smell,41.26% protein conversion and 69.6% peptide content could be obtained by enzymatic hydrolysis of pepsin and trypsin at 40 ℃ and p H 5 for 3h.When the antioxidant peptide concentration of fly maggot was in the range of 8000-1000 UG/ml,the DPPH radical scavenging rate was stable at 80.00%-83.50%,the superoxide anion radical scavenging rate was 66.89%-80.33%,and the reducing power was 0.76-0.97.At the same time,the research shows that fly maggot antioxidant peptide powder has good heat resistance,acid and alkali resistance and tolerance to gastrointestinal enzymatic digestion.Experiment 2: the chicken inflammation model was established by the combined action of lipopolysaccharide(LPS)and thrombinTaking 4-day-old AA Broilers as experimental animals,81 experimental chicks were randomly divided into three treatment groups.Each treatment group had three repetitions and nine chickens in each repetition.The test period was 7 days.The blank control group was injected with normal saline,low-dose group(LPS 5 mg/kg +thrombin 150 U/kg)and high-dose group(LPS 10 mg/kg + thrombin 300 U/kg).The effects of LPS combined with thrombin stimulation on growth performance,serum antioxidant and serum indexes of broilers were studied.The results showed that compared with the control group,under the condition of LPS combined with thrombin stress,the low-dose group and high-dose group significantly increased the content of MDA in serum at 12 hours(p<0.05),and decreased the contents of T-AOC and GSH-Px(p>0.05).At the same time,the level of NO(nitric oxide)and inflammatory factors IL-1β,IL-6,TNF-α in liver increased.Clinical autopsy can obviously observe the bleeding of liver tissue,and HE staining can observe the bleeding,hemolysis and a small amount of exudate infiltration of liver,thymus and spleen,indicating that LPS combined with thrombin stimulation can establish the inflammation model of chicks.Among them,the pathological changes of low-dose effect are more obvious.Experiment 3: antioxidant effect of fly maggot antioxidant peptide on SPF broilers induced by LPS and thrombinUsing the inflammation model of 4-day-old AA Broilers as experimental animals,108 4-day-old SPF AA Broilers weighed 55 ± 5 g.The chicks were randomly divided into 6 treatments,with 3 repetitions in each treatment and 6 chickens in each repetition.The experimental groups were control group,model group(5 mg/kg LPS +150 U/kg thrombin),VC group(5 mg/kg LPS + 150 U/kg thrombin + 50 UG/kg VC),low concentration peptide group Ⅰ(5 mg/kg LPS + 150 U/kg thrombin + 5 mg/kg maggot peptide),medium concentration peptide group Ⅱ(5 mg/kg LPS + 150 U/kg thrombin + 10 mg/kg maggot peptide),high concentration peptide group Ⅲ(5 mg/kg LPS + 150 U/kg thrombin + 15 mg/kg maggot peptide).To study the effects of fly maggot antioxidant peptides on growth performance,immunity,serum indexes and digestive function of inflammatory model broilers.The results showed that under the condition of LPS combined with thrombin stress,oral administration of fly maggot antioxidant peptide could significantly reduce the content of MDA in serum(p<0.05)and increase the contents of T-AOC,GSH-Px and SOD(p<0.05).At the same time,it can improve immunity and reduce the content of NO(nitric oxide),IL-1 β,IL-6,TNF-α and IL-10,significantly increase the V/C ratio of duodenum and jejunum.In general,there is no significant difference between oral administration of 15 mg/kg and 25 mg/kg maggot peptide on the growth performance and immune function of chicks.In order to improve the production needs and reduce the cost,it is determined that the optimal addition amount of maggot peptide is 15 mg/kg. |
