| Because of the problems such as antibiotic resistance of bacteria,drug residues,and food safety as a result of the overuse of feed antibiotics,several countries have restricted or even banned the use of antibiotics in the feed since the 1980 s.Our country has moved into an age where the antibiotics were completely banned in the feeds of livestock and poultry from 1 July 2020.Plant extracts exhibit the potential to replace the use of antibiotics in the feed due to their green and safe biological characteristics,and they therefore show a broad application prospect in animal production.In this regard,this study combined in vitro and in vivo experiments to explore the effects of two combination products of plant extracts(made up of curcumin,cinnamaldehyde,thyme,phytosterol,astragalus polysaccharide,allicin,and carvacrol in an optimized way)on the growth performance and hepatic functions of pigs.This study might provide novel clues and scientific basis to the application of plant extracts in animal husbandry.This study consists of three experiments as follows.Based on the preliminary research of our team,the experiment 1 selected curcumin,cinnamaldehyde,thyme,phytosterol,astragalus polysaccharide,allicin,and carvacrol as objects to analyze their antioxidant abilities in vitro.In this study,we used the butylated hydroxytoluene as a reference substance and investigated the capacity of the above plant extracts to scavenge free radicals through the analysis tests of diphenyl picrylhydrazyl,2,2’-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)diammonium salt,and superoxide anion radicals,respectively.The results revealed that: curcumin,cinnamaldehyde,thyme,phytosterol,astragalus polysaccharide,allicin,and carvacrol exhibited favorable antioxidant capacity and were able to decrease the concentrations of several free radicals in vitro.Experiment 2 was carried out to study the effect of two combination products of plant extracts on the growth performance and hepatic antioxidant and immune function of growing-fattening pigs.A total of 120 cross-breed(Duroc × Landrace × Yorkshire)weaned piglets with similar body weight and health condition were selected at 28 days of age,and then divided into 4 treatment groups.Each treatment group consists of 6 replicates and 5piglets per replicate.Piglets in the antibiotic-free control group fed the basic diets with no antibiotics(NC group),while the remaining were fed with the basic diets containing antibiotics(AC group),the combination product I of plant extracts(CI group),or the combination product II of plant extracts(CII group).All piglets were fed up to 130 days of age.In the end of the feeding experiment,one pig from each replicate was randomly selected for the collection of blood and liver samples.The results revealed that:(1)dietary supplementation with two combination products of plant extracts had no effect on the final body weight at 130 days of age and the average daily feed intake,average daily gain,and feed/gain ratio from 75 to 130 days of age,when compared with the NC group(P > 0.05).(2)Compared with the NC group,the AC and CI groups had the increases in hepatic glutathione peroxidase(GSH-Px)activities(P < 0.05),while CII group exhibited a significant increase in reduced glutathione content(P < 0.05);supplementation with the two combination products of plant extracts remarkably decreased the content of hepatic malondialdehyde(MDA;P < 0.05).(3)Feeding the pigs with the combination products of plant extracts significantly up-regulated the m RNA expression level of hepatic superoxide dismutase 1(SOD1)compared with the NC group(P < 0.05);the CI group also showed an obviously enhanced expression of hepatic glutamate-cysteine ligase modifier subunit(GCLM)m RNA than that in the NC group(P < 0.05).In comparison with the AC group,the CI group had greater m RNA abundance of nuclear factor erythroid derived 2 like 2(Nrf2),glutathione peroxidase 1,glutathione peroxidase 4,glutathione reductase,GCLM,and SOD1(P < 0.05),while CII group also had increased levels of glutamate-cysteine ligase catalytic subunit and SOD1 m RNA(P < 0.05).(4)By comparison with the NC group,the content of hepatic interleukin 1β(IL1β)was decreased significantly in the AC,CI,and CII groups(P < 0.05).The content of hepatic interleukin 10 was remarked higher in the CII group than the other groups(P < 0.05).(5)In contrast to the NC group,the AC,CI,and CII groups showed significantly decreased m RNA expression of toll-like receptor 4,myeloid differentiation primary response gene 88,and IL1β in the liver(P < 0.05).The AC and CI groups had a remarkable decrease in the expression of tumor necrosis factor alpha m RNA than that in the NC group(P < 0.05).Experiment 3 was conducted to investigate the effect of two combination products of plant extracts on the plasma and hepatic lipid metabolism in the growing-fattening pigs.The trial design and methods were similar with the experiment 2.The results revealed that:(1)The AC,CI,and CII groups showed significantly decreased contents of plasma total cholesterol(TC),total triglycerides(TG)and low-density lipoprotein cholesterol(LDL-C)in comparison with the NC group(P < 0.05).The CI and CII groups had declined TC and LDL-C contents and elevated high-density lipoprotein cholesterol concentration in contrast to the AC group(P < 0.05).(2)By comparison with the NC group,dietary supplementation with the two combination products of plant extracts obviously decreased the content of hepatic TG in the pigs(P < 0.05);the combination product II significantly increased the activities of lipoprotein lipase,hepatic lipase,and total lipase(P < 0.05).(3)Compared with the NC group,the m RNA expression of silent information regulator 1,adenosine monophosphate-activated protein kinase alpha,carnitine palmityl transferase 1 alpha(CPT1α),and peroxisome proliferator-activated receptor α were noticeably increased in the liver of CI group(P < 0.05);the expression of hepatic CPT1α m RNA was also increased in the CII group than that in the NC group(P < 0.05).In conclusion,the main ingredients of the two combination products of plant extracts have favorable abilities to scavenge free radicals;dietary supplementation with the two combination products of plant extracts have no effect on the growth performance of growing-fattening pigs,but they could improve hepatic function by enhancing antioxidant capacity,alleviating oxidative stress,and inhibiting inflammatory responses.The combination products of plant extracts have the capacity to decrease hepatic lipid accumulation and to improve circulating lipid levels. |
