| Objective:In this paper,AA broilers were used as animal models to explore the effects of different doses of Viola yedoensis Makino on growth performance,meat quality,blood biochemistry,cortisol,HSP70 and digestive enzymes of broilers under heat stress.On this basis,the changes of intestinal flora were observed,which provided an experimental basis for developing Viola yedoensis Makino into a feed additive to alleviate heat stress of broilers.Methods:60 1-day-old male AA broilers were randomly divided into 6 groups with 10chickens in each group.Divided into Control group(26±1℃),HS group(33±1℃),VP-H group(26±1℃,4.5%Viola yedoensis Makino),VP-L+HS group(33±1℃,0.5%Viola yedoensis Makino),VP-M+HS group(33±1℃,1.5%Viola yedoensis Makino),VP-H+HS group(33±1℃,4.5%Viola yedoensis Makino),the feeding cycle was divided into modeling The pre-phase(1-28 d)and the heat stress period(28-42 d),a total of 42 d.During the feeding period,the feed intake of each week was measured,the weight of each broiler was measured week by week,and the feed-meat ratio was calculated.After that,one broiler close to the repeated average weight was selected from each repeated group for slaughter performance measurement.Meat samples and tissues were taken after slaughter,and the color,PH,shear force,dripping loss and cooking loss of chest muscle were measured.Serum cortisol,HSP70 and related blood biochemical indexes were measured after sepa-ration.The activities of amylase and lipase were determined after taking duodenal tissue.The mRNA expression of HSP70,Pep T1,B~0AT,EAAT3,CAT1,PPARαand STL27 in duodenum and HSP70,MYOG,MYOD,MYF5,PAX3 and PAX7 genes in chest muscle were detected by q RT-PCR.Analysis of cecal flora in broilers by 16Sr DNA high-throughput sequencing.Results:1)The growth performance and meat quality of broilers were studied.Compared with the control group,the daily feed intake of broilers in normal temperature group was significantly decreased(P<0.05).During heat stress period,the feed to gain ratio of broilers in heat stress model group was significantly increased(P<0.05).Compared with heat stress model group,the feed to gain ratio of broilers in medium-dose and high-dose groups was significantly decreased under heat stress(P<0.05),indicating that adding appropriate amount of Viola yedoensis Makino in the diet can effectively improve the growth performance of broilers under heat stress.Compared with the control group,chest muscle color,shear force and drip loss were significantly increased in heat stress model group,and PH value after 45min was significantly decreased(P<0.05);chest muscle color was significantly decreased and PH value after 45min was significantly increased in medium and high dose groups(P<0.05).However,the shear force of breast muscle was significantly decreased in the medium-dose group under heat stress(P<0.05),and the cooking loss of breast muscle was significantly decreased in the high-dose group under heat stress(P<0.05),suggesting that appropriate addition of Viola yedoensis Makino can improve the chicken quality of broilers under heat stress.Compared with the control group,the activities of lipase(LPS)and amylase(AMS)in duodenum of broilers in heat stress model group were significantly decreased(P<0.05),and the digestive enzyme activities in duodenum of broilers were restored to a certain extent by the addition of amylase(AMS)in heat stress model group,except the LPS activity in low dose Viola yedoensis Makino group(P<0.05).There were no significant differences in the activities of LPS and AMS in the other groups compared with the heat stress group(P>0.05),and the duodenal digestive enzyme activities of broilers under heat stress were improved to a certain extent.2)The blood biochemistry of broiler chickens showed that compared with the control group,the high-dose Viola yedoensis Makino at room temperature group significantly decreased the serum lactate dehydrogenase(LDH)and Creatine Kinase(CK)contents of broiler chickens(P<0.05).Under heat stress conditions,the three doses of Viola yedoensis Makino group further significantly decreased the content of CK in serum(P<0.05),while the content of LDH was significantly decreased in the middle dose of Viola yedoensis Makino group(P<0.05).Compared with the control group,the content of leukocyte ratio(A/G),total protein(TP)and globulin(GLO)in the serum of the heat stress model group decreased to a certain extent(P>0.05),the albumin(ALB)content decreased significantly(P<0.05),while the addition of three doses of Viola yedoensis Makino under heat stress conditions restored the serum A/G and ALB content to a certain extent(P>0.05).The content of GLO was significantly increased in the dose of Viola yedoensis Makino group(P<0.05).3)When measuring heat stress indicators,it was found that at 35 days of age,compared with the control group,the serum cortisol content of the heat stress model group was significantly decreased(P<0.05),and the serum HSP70 content was significantly increased(P<0.05);Under heat stress conditions,adding low and high doses of Viola yedoensis Makino increased the content of serum cortisol to a certain extent(P>0.05),and the serum cortisol levels in the middle and high doses of Viola yedoensis Makino groups were further decreased(P>0.05).Except for the high dose,the other doses of Viola yedoensis Makino group significantly decreased the content of serum HSP70 under heat stress conditions(P<0.05).At 42 days of age,compared with the control group,the serum cortisol content of the heat stress model group was significantly decreased(P<0.05),and the serum HSP70content was significantly increased(P<0.05).The content of serum cortisol was further reduced under heat stress conditions,among which the low and high doses of Viola yedoensis Makino were significantly different from the heat stress group(P<0.05).At the same time,the three doses of Viola yedoensis Makino were still in certain To some extent,the content of serum HSP70 was reduced(P>0.05).Notably,serum cortisol and HSP70levels in 42-day-old broilers were significantly higher than those in 35-day-old broilers(P<0.05).At the end of the experiment,the mRNA levels of HSP70 in the duodenum and muscle tissue were detected.Compared with the control group,the heat stress model group significantly increased the mRNA expression of HSP70 in the duodenum of broilers(P<0.05),while There was no significant change in HSP70 mRNA in muscle(P>0.05);under heat stress conditions,all doses of Viola yedoensis Makino group except for the middle dose significantly decreased the mRNA expression of HSP70 in the duodenum of broilers(P<0.05).However,only low-dose Viola yedoensis Makino significantly reduced the expression of muscle HSP70 mRNA(P<0.05).4)The q RT-PCR experiment found that compared with the control group,heat stress significantly decreased the mRNA expressions of STL27,B~0AT1,PEPT1,CAT1,EAAT3and PPARαin the duodenum(P<0.05).The addition of three different doses of Viola yedoensis Makino group will increase the mRNA expression of STL27,B~0AT1,PEPT1,CAT1,EAAT3 and PPARα,especially in the low-dose Viola yedoensis Makino group under the effect of heat stress(P<0.05).Compared with the control group,the heat stress modeling group significantly decreased the mRNA expression of MYOD and PAX3 in broiler muscles(P<0.05),and significantly increased the mRNA expression of MYF5(P<0.05),PAX7 and MYOG mRNA There was no significant change in expression level(P>0.05).Compared with the heat stress model group,the addition of three different doses of Viola yedoensis group increased the mRNA expression of MYOG,MYOD,MYF5,PAX3 and PAX7 genes,especially the middle dose of Viola yedoensis Makino group had significant effect under heat stress.(P<0.05).5)At phylum level,the abundance of beneficial bacteria in cecum of broilers was increased and the abundance of harmful bacteria was decreased in Viola yedoensis Makino group.It also increased the abundance of beneficial bacteria and decreased the abundance of harmful bacteria at the taxonomic level.The results of Beta diversity analysis showed that the structure of intestinal microflora in cecum of broilers was changed.Compared with the control group,the abundance and diversity of intestinal microflora in heat stress group were decreased,while the abundance and diversity of intestinal microflora in Viola yedoensis Makino group were improved,and the growth of harmful bacteria was reduced and the colonization of beneficial bacteria was increased.Conclusion:To sum up,the thermal stress a variety of effects on the chicken body,including the content of serum cortisol and HSP70,growth performance,meat quality,duodenal digestive enzyme activity,blood biochemical indicators,duodenal nutrients transport carrier and muscle growth factors,and cecum intestinal flora,which reduces the poultry farming and economic benefits.The negative effects of heat stress can be effectively improved by adding Viola yedoensis Makino to the diet,and the appropriate concentration is 0.5%-1.5%.Therefore,it provides a theoretical basis for the application of Viola yedoensis Makino as a safe Chinese herbal feed additive for heat stress resistance in broiler breeding. |
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