Mechanisms Studay Of Selenium-enriched Probiotics Improving Growth Performance And Meat Quality Of Chickens And Resisting Coccidiosis Infection

Selenium(Se)is an essential element for a wide range of species,including birds and human.Se plays an important role in immune functions,aging as well as reproduction.Selenium,as a component of the glutathione peroxidase(GSH-Px),prevents oxidative damage to body tissue.For domestic animals,Se supplementation in the diet could improve meat quality,for example,the texture characteristics or color of chicken meat,pork and beef.Probiotics was defined as a live microbial feed supplement which confers a health benefit on the host animal by improving the intestinal microbial balance.Probiotics has the positive impacts on the poultry performance,nutrients digestibility,lipid regulation and feed consumption in layers and broilers.The aforementioned studies indicated that selenium or probiotics may help to improve health,performance and meat quality of the birds and fill the gap between requirement and availability of high quality meat for human consumption.Avian coccidiosis is the most common,harmful and deadly protozoan disease leading the various degrees of oxidative stress,inflammation,diarrhea,and immune suppression and so on.Currently,the poultry industry relies heavily on anticoccidial drugs to prevent and treat coccidiosis.It resulted in many disadvantages,and the serious problems are drug resistance and residue.Consequently,it is an urgent need to find new and alternative ways for controlling coccidiosis in poultry.Se-enriched probiotics possesses the combination effect of selenium and probiotics.So we investigated the effects of selenium-enriched probiotics on growth performance,antioxidant status and meat quality of healthy chicken and on intestinal immune function and antioxidant status of chickens challenged with Eimeria tenella.Experiment 1 Effects of dietary selenium-enriched probiotics supplementation on growth performance,meat quality and antioxidant status in broilersThe two hundred one-day-old male broilers(Ross 308)randomly allotted to four dietary treatments were fed for 42 days.Birds were fed a basal diet(Con,0.11 mg Se/kg)or basal diets with added probiotics(P,0.11 mg Se/kg),sodium selenite(SS,0.41 mg Se/kg),or SP(0.41 mg Se/kg).The results showed that adding SP significantly increased average daily gain(ADG)and decreased feed/gain ratio(F/G)of broilers.Compared to Con group,Se contents of blood and tissues,and the activities of glutathione peroxidase(GSH-Px),superoxide dismutase(SOD)and catalasa(CAT)of breast muscles were increased in SP or SS group,while the malondialdehyde(MDA)levels significantly decreased in SP,SS,or P group.All added diets significantly decreased the total cholesterol(TC),low-density lipoprotein cholesterol(LDL-C)and the triglyceride levels in breast muscles,but they did not have influence on high-density lipoprotein cholesterol(HDL-C)level.The added diets also significantly decreased the drip losses(DL)and L*(lightness)values and increased a*(redness)and b*(yellowness)values in breast muscles.SP had maximum beneficial effects among the added diets.It could be concluded that SP is a potential feed additive in improving growth performance,antioxidant ability and meat quality of broiler.Experiment 2 Effects of selenium-enriched probiotics on growth performance,oocyst shedding and cecal lesions of chickens challenged with Eimeria tenellaOne hundred and fifty one-day-old Chinese yellow chickens randomly allotted to five dietary treatments of 30 each were fed for 42 days.The birds were fed a basal diet(Con,0.11 mg Se/kg),a basal diet(PC,0.11 mg Se/kg)or basal diets with probiotics(P,0.11 mg Se/kg),sodium selenite(SS,0.41 mg Se/kg),or selenium-enriched probiotics(SP,0.41 mg Se/kg).At 21 days of age,the chickens in PC,P,SS,and SP groups were orally inoculated with 5×104 E.tenella oocysts.The fecal samples were collected from days 3 to 7 post infection.On the 7 d post-challenge,gross lesion scores of cecum are observed.The results showed that the PC group had the lowest weight gains(89.11g),the most severe cecal lesions(3.8),and the most number of oocyst output(1.34×106)in the five groups.The SP showed better effects of improving weight gains,alleviating cecal lesions,and reducing oocyst shedding compared to SS or P.At 1?42 days of age,compared to Con group,ADG and ADFI were decreased in PC group,while the F/G significantly increased.There were no significant difference for ADG and ADFI between the Con group and SP group,but the F/G significantly decreased in SP group.Experiment 3 Effects of selenium-enriched probiotics on intestinal selenium contents and antioxidant status of chickens challenged with Eimeria tenellaExperiment design is same as the experiment 2.On 7 and 21 d postcoccidial challenge(28 and 42 day post-hatch),ten chickens in each group were sacrificed and their duodenum and cecum were removed.On the 7 d post-challenge,compared to Con group,Se contents and the activities of GSH-Px and SOD of intestine were decreased in PC group,while the activities of CAT and the MDA levels significantly increased.However,SP or SS elevated the Se contents and the activities of GSH-Px,SOD and CAT of intestine,but lowered the MDA levels.And the effect of adding SP was better than that of SS.There was no significant difference for Se contents between the PC and P groups,but the MDA levels in P group lower than that in PC group.On the 21 d post-challenge,intestinal Se contents and antioxidant status significantly increased in SP or SS group.There was no significant difference for Se contents among the Con,PC,or P groups.And the intestine antioxidant status of PC group was similar to Con group's.Experiment 4 Effects of selenium-enriched probiotics on intestinal immune function of chickens challenged with Eimeria tenellaExperiment design is same as the experiment 2.This study was conducted to investigate the effects of selenium-enriched probiotics on the contents of secretory immunoglobulin A and interleukin 2(IL-2),the numbers of CD4+ and CD8+ T lymphocytes of cecum and the mRNA levels of glutathione peroxidase 2(GPx2),selenoprotein W(SeW)and IL-2.On the 7 d post-challenge,compared to Con group,these indexes were significantly increased in PC,SS,P,or SP group.And the SP group showed significant increases in these indexes compared with the PC,SS,or P group.On the 21 d post-challenge,SS,P,or SP significantly elevated the contents of sIgA and IL-2 and the mRNA levels of IL-2.SS or SP significantly increased the mRNA levels of GPx2 and SeW.However,there were no differences in these indexes between the Con and PC groups.