The MRNA Expression Of CaBP-D28k \ OVA And Egg Quality Changes In Oviduct Of Egg-laying Hens Infected With NDV

Newcastle disease(ND) is a highly contagious acute disease caused by Newcastle disease virus(NDV) in avian. In addition to morbidity and mortality, NDV can also cause severe leision in the reproductive system of laying hens, and result in decreased egg production and quality(sand shell eggs, soft shell eggs and misshapen eggs, etc). However, the mechanism by which NDV infection on oviduct tissue pathological changes and poor eggs quality decline remains not well understood.In this study, 240-day-old Lohmann white hens were challenged with NDV/Chicken/TC/1/2011 through combined intraocular and intranasal routes. At 1, 3, 5, 7, 9, 11 and 15 days post infection(p.i.), eggs from both the infection group and control group were collected for detection of eggshell quality. The eggshell calcium contents were measured by flame atomic spectrophotography, and scanning electron microscope was used to analyze the ultrastructure of the eggshell inner surface, outer surface and transversal surface. A certain number of laying hens from each group were euthanized at 1, 3, 5, 7, 9, 11 and 15 p.i., the bulge and uterine part of fallopian tube were collected to determine the m RNA levels of Ca BP-D28 k and ovalbumin(OVA) gene by real-time quantitative PCR. The results were as below:1. At 1, 3, 5, 7, 9, 11 and 15 days p.i., the correspondent average relative contents of eggshell calcium(mass ratio) of the infected laying hens were 40.60%, 38.41%, 34.15%, 37.42%, 38.58%, 39.03% and 39.50%, respectively, while that of the control laying hens was 41.88%; the mean eggshell thickness of transversal surface of the infected laying hens was 305μm, 290μm, 279.5μm, 313μm, 320.50μm, 321μm and 323μm, respectively, while that of the control laying hens was 368.5μm; At 1-5 days p.i., mammillary layer got thinner, smoothness and compactness of the palisade and vertical crystal layers suffered a drop to various degrees; cuticle layer on the outer surface of the eggshell roughed gradually, stoma increased and cracked significantly; spaces between collagenous fibres on the inner surface of the eggshell increased gradually, the structure was sparse and broken obiviously, nodes significantly less; At 7-15 days p.i., eggshell quality improved gradually.2. At 1-5 days p.i., hens in the infected group laid soft-shelled and shell-less eggs, the level of Ca BP-D28 k m RNA in the uterine part of fallopian tube was decreased continuously, the gene expression level was only 16% of that in control group at 5 days p.i.; At 7-15 days p.i., eggshell quality improved gradually, and the level of Ca BP-D28 k m RNA in the uterine part of fallopian tube was gradually recovered, the gene expression level was 45% of that in control group at 15 days p.i..3. At 1, 3, 5, 7, 9, 11 and 15 days p.i., the relative contents of protein in albumen of the infected birds were 10.39%, 9.71%, 9.32%, 9.51%, 9.75%, 9.93% and 10.35%, respectively, while that of the control was 11.05%, At 1-5 days p.i., the level of OVA m RNA in the oviduct bulge decreased continuously, the gene expression level was only 5% of that in control group at 5 days p.i.; At 7-15 days p.i., the level of OVA m RNA in the oviduct bulge, the gene expression level was 27% of that in control laying hens at 15 days p.i..These results show that, after infection with NDV, eggshell calcium contents positively correlated with eggshell quality and the level of Ca BP-D28 k m RNA in the uterine part of fallopian tube; protein level in egg white positively correlated with the level of OVA m RNA in the oviduct bulge.