Study On The Effect Of Induced-molting On Performance,Plasma Hormone Level And Ovarian Function Of Laying Hens

Poultry molting is the periodic shedding and replacement of feathers.The reproductive function of laying hens declines during natural molting.The production performance maintained very low in a long period of this time.Mandatory molting allows the birds to molt quickly and restore high production performance.Rejuvenating and realizing the production potential of laying hens are also important technical ways to improve the economic benefits.This experiment uses starvation method to perform induced-molting on laying hens,comparing with the basic diet feeding group?without induced-molting?,to study the effects of induced-molting by starvation on production performance,immune performance and reproductive hormone.Ultimately using transcriptomics technology to find the differential gene expression in different physiological states of ovarian tissue,and exploring the molecular mechanism of induced-molting to regulate the recovery of ovarian function in the second laying cycle of laying hens.This study also provide a theoretical basis for revealing the mechanism of reproductive regulation in laying hens after molting,in order to better serve production practices.Exp.1 Effect of induced-molting on the production performance and egg quality of laying hensThis study aimed to investigate the effect of induced-molting by starving on production performance and egg quality of late-phase laying hens.A total of 13,876 laying hens of Jinghong No.1 on 449 days were selected for the experiment of induced-molting by starving.The results demonstrated that the body weight of the birds population decreased by 30.09%after a 15-day-long starving treatment,meeting the requirement of feeding resuming;The weight loss rate of chickens with lower starting-weight was found significantly increased compared to that of the chickens with higher starting-weight?P<0.05?;The birds stopped laying eggs after a 12-day-long starving treatment;Eggs were started to appear on the 10^thday of feeding resuming period,the laying rate exceeded 85%at the 6^thweek;The mortality of the chickens was 0.66%during starvation period,and the mortality from 9^thto15^thday was significantly higher than 1^stto 4^thday?P<0.05?;The mortality of the chickens during 19days within feeding resuming period was 0.85%,a significantly higher mortality was observed from 1^stto 4^thday during feeding resuming period?P<0.05?;Egg weight,eggshell strength and albumen height increased after molting.The combined data suggest that the induced-molting technique by starving has a good application effect on the Jinghong No.1laying hens,which can effectively improve the production performance and egg quality of aged laying hens.Exp.2 Effect of induced-moltingon blood biochemical indicators and reproductive hormone content of laying hensThis study aimed to investigate the effects of induced molting on blood biochemical indicators and reproductive hormones of late-phase laying hens.Six hundred 449-d-old Jinghong layers were randomly assigned into 2 groups of 10 replicates each,with 30 birds per replicate.The experimental group implemented the induced-molting technique?starved for 15 days?,and the control group fed basal diet without induced molting.The results indicated that after molting,the immune performance of the experimental group is improved compared with the control group?P>0.05?;the alanine aminotransferase?ALT?and aspartate aminotransferase?AST?levels in the experimental group were significantly lower than those in the control group?P<0.05?.The plasma alkaline phosphatase?AKP?level in the experimental group was significantly higher than that in the control group?P<0.05?.The plasma levels of Tetraiodothyronine?T₄?,estrogen?E₂?,luteinizing hormone?LH?,follicle-stimulating hormone?FSH?and prolactin?PRL?in the experimental group were significantly higher than those in the control group?P<0.05?.The combined data suggest that induced-molting can effectively improve the reproductive function by regulating the changes of reproductive hormones.Exp.3 Molecular mechanisms of induced-molting by starvation on ovary restoration in laying hens based on transcriptomicsOvarian transcriptome sequencing was used to study the transcriptome differences of ovarian tissues in different physiological states of laying hens,and to find the regulatory mechanism that affects the differential expression of genes related to the second egg-laying cycle at the molecular level.Experiment design of Exp 3 was similar with Exp 1.The results showed that the 52,222 differen genes were screened for sequencing,of which 17,198 were known genes and 35,024 were new genes.18 865 genes were significantly different on expression,of which 3,637 were known genes and 15,228 were new genes.Among the significant different expression genes,11,922 were up-regulated and 6,943 were down-regulated.Functional analysis showed that 8,340 different expression genes were mapped to 12,162 GO terms,85 of which were significantly enriched,and 9,742 different expression genes were annotated to 342 KEGG pathways,including 32 significantly enriched pathways.In addition,188 differential genes annotated to the biological processes related to reproduction,and 513 differential genes were annotated to 7 reproduction-related pathways.ADCY,RXRG,KRT,MMP,PRLR,and ESR genes can be used as candidate genes related to reproductive traits that affect the recovery of ovarian function in the second laying cycle.Conclusions:?1?Induced-molting can effectively improve the production performance and egg quality of the second laying cycle of the laying hens,extend the economic life of the hens,and increase production efficiency.?2?The induced-molting can improve the immune performance of laying hens in the late laying period,and has certain protective effects on liver function.Moreover,the induced-molting by starvation can regulate the recovery of ovarian function by regulating the changes of reproductive hormones in laying hens,and then regulate reproductive function of laying hens.?3?.Transcriptome sequencing was performed on ovaries in different physiological states,and 35,024 new genes were discovered,and 18,865 significantly differently expressed genes were screened.There were 188 differential genes annotated to the biological processes related to reproduction,and 513 differential genes were annotated to 7 pathways related to reproduction.ADCY,RXRG,KRT,MMP,PRLR,and ESR genes can be used as related candidate genes for studying reproductive traits.Previous studies have shown that genes such as MMP,PRLR,and ESR are closely related to reproductive traits,and these genes can be used as important candidate genes for ovarian function recovery after moulting for further research.