| Oregano essential oil is a kind of essential oil extracted from the Chinese traditonal drug-origanum vulgare.Because of its antibacterial and flavouring properties,it is often used as a food preservative,flavouring agent,preservative or functional ingredient.Oregano essential oil is a feed additive approved by the Ministry of Agriculture and Rural Affairs and is widely used in livestock and poultry breeding.It has the functions of increasing animal feed intake,promoting growth,antibacterial,anti-inflammatory,and anti-parasitic.It is safer and more efficient than traditional feed additives,and it is easily absorbed by the body and has no residue.It is a green feed additive with huge application and development potential.In this study,gibel carp(Carassius auratus gibebio)as the object,7 oregano essential oil supplement groups were designed for breeding experiments,namely N0(0 mg/kg,the control group)、N1(25 mg/kg)、N2(50 mg/kg)、N3(100 mg/kg)、N4(200 mg/kg)、N5(400 mg/kg)and N6(800 mg/kg),the experimental period is 8weeks.In order to explore the effects of adding different amounts of oregano essential oil in the basal diet on the growth performance,digestive enzyme activity,intestinal morphology,intestinal flora,antioxidant and non-specific immunology of gibel carp,and Aeromonas hydrophila was used to challenge to analyze the effect of oregano essential oil on the ability of gibel carp against pathogen infection.The main content and experimental results of this article are as follows:1.The effect of oregano essential oil on the growth performance and digestive enzyme activity of gibel carpSampling after 8 weeks of breeding experiment,the growth performance and intestinal digestive enzyme activity of gibel carp were measured.The results showed that the weight gain,condition factor and specific growth rate of gibel carp with 400mg/kg group and 800 mg/kg group were significantly higher than those of the control group(P<0.05),and the feed coefficient was significantly reduced(P<0.05);Compared with the control group,trypsin,lipase and α-amylase activities in the 200mg/kg group and 400 mg/kg group were significantly increased(P<0.05);2.The effect of oregano essential oil on the intestinal morphology,intestinal flora and liver function of gibel carpThe thickness of the posterior intestinal wall,villus height,villi width and the number of goblet cells in the experimental group with the addition doses of 200 and400 mg/kg were significantly higher than those in the control group(P<0.05);In the analysis of intestinal flora,the experimental groups with different dosages did not affect the abundance of intestinal flora(P>0.05).There was no significant difference in total cholesterol(TC)and triglyceride(TG)in each experimental group compared with the control group(P>0.05);the content of urea(UREA)in the experimental group at 200 mg/kg group,400 mg/kg group and 800 mg/kg group was significantly reduced(P<0.05).3.The effect of oregano essential oil on the antioxidant function,non-specific immunity and anti-pathogenic infection of gibel carpAntioxidant indexes such as superoxide dismutase(SOD),catalase(CAT),total antioxidant capacity(T-AOC)and malondialdehyde(MDA)content of gibel carp in the experimental group were no significant difference from those in the control group(P>0.05);The total protein,albumin and complement C3 of 200 mg/kg group and400 mg/kg group were significantly higher than those of the control group(P<0.05);After Aeromonas hydrophila challenged,the survival rate of 200,400 and 800 mg/kg group was significantly higher than that of the control group and the relative percent survival of 400 and 800 mg/kg group was significantly higher than that of 25,50,100mg/kg group(P<0.05). |
