Mechanism Exploration For Translucent Egg Formation

Translucent egg is mainly caused by water penetration and accumulation of egg contents in the eggshell.Under natural light,the spots in translucent eggshell were water-like,and in the LED light penetration spots in eggshell were translcuent.Translucent eggs appear in many laying hens,which greatly affect the appearance of eggs and reduce the commercial value of eggs.Internationally Reports of translucent eggs have been for 90 years and many experiment were performed,but the basic occurance and genetic characteristics,structural differences and the formation mechanism is still in vague.In the study,an food saving Dwarf brown hens(DWL)and Whiht Leghorn line(WLL)were used to investigate the measurement method for translucent traits,the basic accurance characteristics of translucent eggs,the influence of translucent spots on individual production perforamance and genetic parameters of translucent traits.Results are as follows:four-level grading method was accurately and efficiently for translucent egg classif;the translucent spot penetrated the whole mineralized layer of the eggshell and heritability of the translucent eggs of 63 weeks individual was 0.22.We selected translucent eggs(4th grade)and opaque eggs(1th)for egg quality and weight loss measurement and result are as follows:eggshell strength and eggshell thickness of translucent eggs were significantly higher than those of the opauel group(P<0.05),and egg shell membrane thickness was significantly lower than that of opaque group;there was no significant diffenrence of weigth loss between translucent and opaue eggs within 4 weeks.In future,we measured microstructure of eggshell and physical characteristics of eggshell membrane in 42 weeks DWL and 50 weeks WLL.The same with previous study were found on DWL line,and just eggshell strength is significantly higher in translucent eggs than that of opaque egg in WLL.Ultimate failure stress(UTS)of eggshell membrane in translucent eggs is significantly lower than that of opaue eggs in both lines.Besides,on quantity of gas pores,ultrastructural pores as quantity of bubble pores,area of bubbule pores,there was no significant difference between translucent and opaue eggs.In addition,the content of amino acids in the eggshell membrane(86.36%),proline and lysine were significantly lower than those of the opaue eggs(86.36%)(P<0.05).To locate functional genes associated with translucent eggshell,this study made the whole genome SNPs association analysis with translucent traits using the 600K-gene chip developed by Affymatrix Corp..Association analysis was performed on 96 individuals laying translucent eggs in 3 continuous days and 96 hens laying opaue eggs in 3 continuous days from 1200 500-days WLL,and quality control,gene inputation and population stratification correction were performed before association analysis.As a result,4 SNPs significantly(rs318150079,rs15150251,rs313637053 and rs316987262)and 170 SNPs suggestive significantly associated with translucent eggs were found,which were mainly located on chromosome 2 and 19.Meanwhile,4 significant SNPs are linked and corresponding with 8 genes and 3 QTLs,and 170 suggestive significant SNPs are corresponded to 23 genes.Combined with the previous research results and results of the current experiments,it indicates that the poor toughness of eggshell membrane may the key point for translucent eggshell formation,which made contents penetration in eggshell memabrane and accumulate in eggshell easier in translucent eggs.Besides,thicker eggshells and higher eggshells made the translucent spot in eggshell more serious.In conclusion,the studying investigated method for translucent eggshell measurement,and ensured the translucent spots penetrating the whole mineralized layers,calculating heritability(0.22)and other genetic parameters of translucent eggs.The study also investigated eggshell structure?shell membrane structure and chemical composition,and reveals SNPs,genes and genomic region associated with translucent eggs,which provide basis for the further study of the formation mechanism and molecular mechanism of translucent spots formation.