Effect Of Cadmium Pollution On Hatching Eggs And The Assessment Of Vitamin C Antagonized Cadmium-induced Toxicity In Chick Embryos

China dominates the most position in poultry breeding,whose production of poultry meat and eggs are in the leading position in the world.The data of survey in recent years have showed that the domestic production of chicken and eggs could not meet the need of Chinese people.Additionally,the gap between supply and demand of poultry products is gradually expanding.Therefore,the problem of poultry production capacity is not only related to economic benefits in poultry breeding,but the issue is also involved in the livelihood of people.The widely use of the land and minerals will promote the release of cadmium with the process of industrialization.There are a lot of reports about the cadmium pollution in our country.The risk of cadmium pollution is existed in all segments of the poultry breeding such as the farm selection and chicken feeding.It has been attracted widespread attention about the problem of cadmium pollution in water source and poultry feeding.People have also pay attention to the impact of the chicken’s growth with cadmium pollution.However,egg laying is also an effective way for chicken to excrete environmental pollutions.Therefore,it should be paid more attention to the problem of cadmium pollution in chicken’s eggs.In order to clarify the impact of cadmium pollution on hatching eggs,the study conducted a statistical analysis of cadmium content in eggs and egg products on sale in some provinces in published literature and we also traced the reason of cadmium pollution in eggs and its products.The study takes the E0 eggs as the research issue to simulate the fact situation of cadmium pollution on eggs.According to the data of cadmium pollution on eggs obtained in the literature,we set up three groups of different cadmium dose(1 μg/kg,7 μg/kg,and 49 μg/kg).The study will explore the effects of cadmium pollution on egg hatching with the statistics of chicken embryo mortality rate,chick hatching rate,and the analysis of physical disability chicks in the breeding stage.The developmental toxicity mechanism of cadmium-induced death of chick embryos was speculated according to the morphological changed of chick embryos during incubation.And the levels of superoxide anion and antioxidant function in chick embryos were detected.Additionally,the apoptosis-related protein expression in chick embryo tissues were also tested.The study would search for cheap and effective antagonists based on the toxicity mechanism of the death of chicken embryos and the reduction of hatching rate with cadmium pollution.Additionally,we also used the in ovo feeding of vitamin C to evaluate the antagonistic effect on the developmental toxicity of cadmium.And the results were as following:(1)It was found that the average level of cadmium in eggs and egg products sold in supermarkets in some provinces and cities was 10.68 μg/kg,with a median of 7 μg/kg,through the integrated analysis of the published literature.The maximum dose of cadmium that could be detected was 120 μg/kg and the minimum dose was 1 μg/kg.It showed that cadmium pollution was existed in eggs and egg products in some provinces in my country.(2)Some dose of cadmium exposure could cause the increase in the malformation rate of chicken embryos.The symptoms of chicken embryos at different stages are similar,including body wall defect insufficiency.It suggested that cadmium pollution had some toxic effects on the fusion of body wall.Cadmium exposure could induce the increase of mortality rate,and the mortality rate was higher in early stage than last stage of chick embryo development.Cadmium exposure could lead to the decrease of egg hatching rate.It indicated that cadmium had significant embryonic development toxicity to chicken embryos.(3)After hatching,cadmium polluted eggs showed that the hatching window started later than control.The peak hatching period was not obvious,the mortality rate of chicks during the hatching period was increased with cadmium pollution.And the proportion of physical disability chicks was significantly increased with cadmium pollution.We found that the physical disability chicks with weak legs,inability to stand,tibia dysplasia.And it was showed that small kidney organ coefficient,poor yolk sac absorption in physical disability chicks.And high mortality was found with cadmium exposure during the brooding period.It showed that cadmium pollution not only has toxic effects in the developmental stage of chicken embryos,but also showed its toxic effects in the brooding stage.(4)Cadmium induces excessive apoptosis of chick embryos at HH-17 stage,resulting in i body wall defect in chick embryos.On the one hand,cadmium inhibited the expression of Foxo1 by activating AKT1 leading to antioxidant defense system of chicken embryos destroying.And the organ suffered from oxidative damage.The decrease of Foxo1 promoted apoptosis in chick embryos.The elevated ROS promoted the expression of p53.And the elevated p53 inhibited the expression of Nrf2,and it aggravated the production of ROS.This promoted apoptosis.On the other hand,cadmium caused the downregulation of Mdm2 and Pax3,which disrupted the process of p53 ubiquitination.The synthesis of p53 increased with cadmium exposure,while the level of ubiquitination decreased.It promoted the increase of the level of p53 in chicken embryos.Therefore,the level of apoptosis in chicken embryos was increased significantly with cadmium exposure.The body wall defect was occurred in chick embryos with excessive apoptosis.It might be one of the mechanisms of cadmium-induced body wall defect in chicken embryos.(5)In ovo feeding of vitamin C could alleviate the disturbance of cadmium exposure to the antioxidant defense system of HH-17 chick embryos.And it also increased the expression levels of Foxo1 and Nrf2.The level of ROS in chicken embryos was reduced and the levels of p53 was rescued with in ovo feeding of vitamin C.It could mitigate excessive apoptosis caused by cadmium exposure.It indicated that the in ovo feeding of vitamin C could mitigate the body wall defect of chicken embryos caused by cadmium exposure.(6)In ovo feeding of vitamin C could improve the hatching rate of cadmium-polluted eggs.And it could reduce the probability of physical disability chicks caused by cadmium pollution after hatching.This showed that vitamin C mitigated the toxic effects of cadmium in the brooding stage.To sum up,Cadmium pollution could increase the mortality of chicken embryos.the hatching rate of chicken embryos was reduced with cadmium exposure.And it significantly increased the proportion of physical disability chicks after hatching.Cadmium pollution might cause losses to the poultry breeding.This study showed that in ovo feeding of vitamin C could alleviate the oxidative damage caused by cadmium to chicken embryos.In ovo feeding of vitamin C ensured the normal development of chicken embryos.It antagonized the developmental toxicity of cadmium.Additionally,in ovo feeding of vitamin C improved the hatching rate of hatching eggs and the rate of physical disability chicks.Vitamin C is cheap,which can be easily accepted by farms.Vitamin C has a good application prospect in rescuing the losses caused by cadmium pollution in the poultry breeding.