| Exercise is closely related to production performance and meat quality of chicken.However,it is difficult to measure exercise trait,which restricts the research of molecule mechanism underlying this trait in chickens.Therefore,in this study,the daily step counts(DSCs)was used as an index to measure the exercise of chicken to explore the DSCs profile and molecular mechanism in Chinese Wannan chickens,this paper has carried out the following five research:First,a total of 600(half male and half female)1-day-old Wannan chickens with similar hatching weights were selected,and Daily step counts were recorded for all birds between70 and 112 days of age by a pedometer,then to understand the dynamic changes in daily step counts during the development of chickens and further explored the effects of sex and ages on the DSCs.The results showed that the average number of daily steps at 12 and 13 weeks was relatively stable and remained above 19000 steps,but the average number of daily steps at 11 weeks to 14 weeks showed an overall downward trend.At 15 and 16 weeks,the value increased to more than 20000 steps.Although there was no significant difference in the average number of daily steps at 11 to 16 weeks of age,the males always took more steps than the females.Compared with the female birds,the male birds displayed a higher average number of daily steps at 15 and 16 weeks of age(P<0.05).Therefore,sex has a great influence on the DSCs of Wannan chickens,while age has little influence on the DSCs during the 10 to 16 weeks of age.Second,at 112 days of age,based on the average DSCs,respectively,280 male birds and280 females were ranked and divided into groups with the highest(HS),medium(MS)and lowest(LS)step counts.Then,from each group,15 male birds whose step counts were close to the average were selected for production performance,serum biochemistry and tibial strength analyses.The results showed that the DSCs had no significantly effect on the females body weight(P>0.05),while the males body weight of HS group was significantly lower than that of LS group(P<0.05).At 16 weeks of age,comb length in HS group was significantly longer than that in MS and LS groups(P<0.05),but tibia length and tibia circumference were significantly lower than those in MS and LS groups(P<0.05).In terms of carcass performance and meat quality,the percentage of heart weight in HS group was significantly greater than that in MS and LS groups(P<0.05),but the abdominal fat percentage,cooking loss,shear force and drip loss(P<0.05)in HS group were significantly lower than those in LS group(P<0.05),and there was no statistical difference between other carcass performance and meat quality(P>0.05).In terms of serum biochemical,the contents of glucose(GLU),total protein(TP),triglyceride(TG)and cholesterol(CHO)in serum of chickens in HS group were significantly lower than those in LS group,but the high density lipoprotein(HDL)was significantly higher than those in MS and LS groups(P<0.05).In addition,increased DSCs could improve sperm motility and decreasing the rate of sperm malformation.Thirdly,the ASREMLV4.1 software was used to estimate the genetic parameters of birth weight,body weight at 16 weeks of age,average number of daily steps,comb length,comb height,tibia length and tibia circumference of the G1 generation birds using REML algorithm.The results showed that the heritability of all the studied traits were medium or high heritability traits(0.22?0.39)except the average number of daily steps(0.18).In addition,body weight was positively correlated with other traits except for a moderate negative genetic correlation(-0.20)between body weight and average daily walking number.The average number of daily steps showed a high genetic correlation with tibia length.Fourthly,at112 days of age,highest and low average number of daily steps for two tail selected 4 male birds,for the organization of chest muscle transcriptome sequencing analysis.A total of 101 genes were differentially expressed,among which 86 genes were up-regulated and 15 genes were down-regulated in the HS group compared with the LS group.Among them,ANKRD2,MUSTN1,MYOZ2,IFFBP5 and HOPX genes play important roles in muscle growth and muscle fiber type transformation,which may be closely related to the DSCs traits of chickens.Fifthly,complete genome resequencing was performed on Wannan chickens with bidirectional selected DSCs(11 birds with high average number of daily steps and 11 birds with low average number of daily steps).A sliding window approach(50 kb windows sliding25 kb overlapping steps)was applied to calculate the heterozygosity(Pi)and the fixation index(FST),and the top 1% window of FST and LPI/HPI were selected as the selected region.Compared with the LS group,a total of 175 genes were selected by using Fst method and a total of 316 genes were selected by using Pi method in the HS group.A total of 39 superimposed selected genes were screened out by the two methods.These 39 candidate genes were relate to 62 GO categories such as calmodulin binding,oxidation-reduction process,cell adhesion molecule binding,regulation of insulin secretion and arginine-proline metabolism,phenylalanine metabolism and arginine biosynthesis KEGG pathway.Among them,ASPM,NOS2,CADM2 and CAMKMT genes are mainly related to energy metabolism and muscle growth and development.Meanwhile,the calmodulin-binding pathway involved in ASPM and NOS2 genes may be an important pathway affecting the DSCs of chickens.In summary,at 10 to 16 weeks of age,sex is the main factor affecting the DSCs of Wannan chickens,and enhanced DSCs could improve the meat quality,semen quality and tibial strength of cocks.The heritability of DSCs traits were low to moderate(0.18).RNA-seq revealed that ANKRD2,MUSTN1,MYOZ2,IFFBP5 and HOPX genes play important roles in muscle growth and muscle fiber type transformation,which may be closely related to the DSCs traits of chickens.Genome-wide selection analysis(Fst and Pi)revealed that ASPM,NOS2,CADM2 and CAMKMT genes were positively selected in the high step counts and might be candidate genes for the traits of chicken DSCs. |
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