Study On The Effects And Regulatory Mechanisms Of Rearing Systems On The Development Of Reproductive Organs In Male Geese From Different Breeds

With the transformation and upgrading of China’s goose rearing industry from the traditional extensive free-range rearing at the waterside to the modern large-scale,intensive and environment-friendly dryland-rearing systems.Therefore,improving the mating ability of ganders under the dryland-rearing systems has become a hot issue in the goose industry.Therefore,in this study,Sichuan White goose(SW),Gang goose(GE)and Landes goose(LD),were used as the experimental objects.The same rearing and feeding systems were adopted for all ganders during the period from 0 to 10 week of age.Then,these ganders were randomly equally divided into the cage-rearing(CRS)and net-floor mixed rearing(MRS)groups for each goose breed.At 30 and 43 weeks of age,12 ganders were randomly selected from each group per breed to measure the histomorphological indexes of reproductive organs.At 43 weeks of age,more than 20 ganders were randomly selected from each group per breed for massage and semen collection training,and after assessing sexual desire and determining semen quality,the RNA-Seq technology was used to sequence the transcriptome of testicular tissues of various varieties under different feeding methods,and real-time PCR was used for verification.The main experimental results were listed as follows:(1)At the testicular morphological level,at 30 weeks of age,the testicular size and volume of GE and LD in the MRS were significantly larger than those in CRS(P<0.05).At 43 weeks of age,compared with the MRS,those of SW and GE in the CRS were relatively la MGE.At the morphological level of external genitalia,at 30 weeks of age,the size of external genitalia of LD in the MRS was significantly larger than that in the CRS(P<0.05),but that of SW was significantly larger in the CRS than in the MRS(P<0.05).At 43 weeks of age,the length and diameter of external genitalia(P<0.05)were significantly higher in the CRS than in the MRS.(2)At the testicular histological level,at 30 weeks of age,both the number of convoluted tubules and the thickness of spermatogenic upper cortex were significantly higher in the CRS than in the MRS for three goose breeds(P<0.05).At 43 weeks of age,the thickness of spermatogenic upper cortex,the diameter of seminiferous tubules,and the ratio of testicular parenchyma to interstitial tissue were significantly higher in the CRS than in the MRS for LD(P<0.05).The number of seminiferous tubules and the thickness of seminiferous upper cortex were significantly higher in the CRS than in the MRS for GE(P<0.05),while there were no significant differences in these histological parameters for LD(P>0.05).At the histological level of external genitalia,the thickness of collagen layers in the outer genitalia of GE was significantly lower in the CRS than in the MRS(P<0.05).(3)In terms of sexual desire,under the same frequency of artificial massage,the number of times required for three goose breeds to make their cloaca enlarged and their external genitalia erected is less in the CRS than that in the MRS.At the same time,the proportion of individuals that can extract semen after massage is greater in the CRS than in the MRS.In terms of semen quality,the sperm density and semen quality factor(SQF)values of SW and LD were significantly higher in the CRS than in the MRS(P<0.05),the sperm deformity rate of LD and GE was significantly lower in the CRS than in the MRS(P<0.05),while the sperm viability,sperm density,and SQF values of GE were extremely significantly higher in the CRS than in the MRS(P<0.01).The results of correlation analysis between semen quality and reproductive organ morphology showed that there were significant or extremely significant correlations between the morphological parameters of testes and external genitalia and semen quality indicators,and there were stronger correlations between these indicators in the MRS.(4)The results of transcriptome sequencing analysis showed that 282 differentially expressed genes(DEGs)were screened in the tetes of SW between the two rearing systems.These DEGs were significantly enriched in the ECM-receptor interaction,calcium signaling and other pathways,among which some genes including MESD and CD59 may play important roles.There identified 545 DEGs in the testes of GE screened between the two rearing systems.These DEGs were significantly enriched in the Toll-like receptor signaling,ubiquitin-mediated proteolysis and other pathways,among which some genes including KCTD1 and CCKAR may play important roles.There identified 839 DEGs in the testes of LD.These DEGs were significantly enriched in metabolic processes and other pathways,among which some genes including MYCBP and KIF2 C may play important roles.At the same time,there were 16 DEGs that were identified in the testes for each goose breed between the two rearing systems,among which UB2V2 and STMP1 had the most abundant expression.The DEGs identified between the two rearing systems for three goose breeds were significantly enriched in the pathways including cell differentiation and metabolic processes.(5)The results of weighted gene co-expression network analysis(WGCNA)showed that both the brown and cyan module gene clusters were associated with the testicular development of LD,and were significantly enriched in the pathways including redox process,cytochrome P450 metabolic xenobiotics,cell cycle,mismatch repair,and nucleotide resection repair.The pink module gene clusters were associated with the testicular development of SW,and the candidate genes included MMGT1,GAS7,TAF11,MTO1,NOL9,MIER1,FKBP9,and PPME1.After constructing the protein-protein interaction networks,it was found that EP300,EDN1,CITED2,PTGS2,RB1,DNMT1,ESR1,SMAD3,HIF1,ADKK2,WNT3,WNT3 A,WNT4,LRP6,SFRP1,WNT6,and WNT16,as well as the LRP1 gene that connects relevant important pathways may play key roles in regulating goose testicular development,because these genes were significantly enriched in the pathways related to germline proliferation and differentiation and WNT signaling.Finally,the screened key DEGs were validated by real-time PCR,and the results showed that the RNA-Seq results were reliable.In summary,compared with the MRS,the reproductive organ development,sexual desire,and semen quality of ganders from three goose breeds were relatively better in the CRS.At the same time,the signaling pathways such as cell differentiation and metabolic processes may play key roles in mediating the effects of different rearing systems on goose testicular development,while the activity of pathways such as redox processes and cell division may be important reasons for the differences in the testicular development of three goose breeds under the same rearing system.The results obtained from this study not only revealed the effects of different rearing systems on the ganders’ reproductive organ development and semen quality for three goose breeds,laying a scientific basis to the selection of suitable dryland-rearing system for ganders,but they also provided new ideas for the molecular breeding of the mating ability of ganders.