Effect of In Ovo Zinc Injection on the Embryonic Development and Epigenetics-Related Indices of Zinc-Deprived Broiler Breeder Eggs
The role of in ovo zinc (Zn) injection in improving the embryonic development in eggs from Zn-deficient hens, via epigenetic and antioxidant mechanisms, was examined. A completely randomized design involving a 1 (the non-injected control) + 1 (the injected control with sterilized water) + 2 (Zn source) × 2 (Zn level) factorial arrangement of treatments was used. The two injected Zn sources were inorganic Zn sulfate and organic Zn-lysine chelate with a moderate chelation strength, and the two injected Zn levels were 50 and 100 μg Zn/egg. In ovo Zn injection decreased (P < 0.05) embryonic mortality, and increased (P < 0.05) hatchability and healthy chick ratio. In ovo Zn injection increased (P < 0.05) embryonic tibia Zn content, but had no effect (P > 0.05) on copper (Cu)- and Zn-containing superoxide dismutase (CuZnSOD) activities and metallothionein IV (MT4) levels or their mRNA expression levels and malondialdehyde (MDA) levels in the embryonic liver. In ovo Zn injection had no effect (P > 0.05) on the global level of DNA methylation or DNA methylation and histone 3 lysine 9 (H3K9) acetylation levels of the MT4 promoter in the embryonic liver. However, the organic Zn had higher (P < 0.05) levels of DNA methylation and H3K9 acetylation than inorganic Zn. These data demonstrate that in ovo Zn injection improved the embryonic development, and the organic Zn was more effective than inorganic Zn in enhancing DNA methylation and H3K9 acetylation in the liver MT4 promoter, but the precise mechanisms require further investigations.
KeywordsIn ovo zinc injection Chick embryo Metallothionein Epigenetics
The present study was supported by the Agricultural Science and Technology Innovation Program (ASTIP-IAS08; Beijing, P.R. China), the Key International Cooperation Program of the National Natural Science Foundation of China (project no. 31110103916; Beijing, P.R. China), and the China Agriculture Research System (project no. CARS-41; Beijing, P.R. China). In addition, we would highly appreciate Dr. David Masters in the University of Western Australia for assisting with the English editing of this manuscript.
X. Luo was responsible for all issues related to this paper. X. S. and L. L. were responsible for the planning of the study, sample analyses, collections, and statistical analyses of all data, as well as the manuscript writing. X. L. and L. Z. were involved in the sample collections. X. L. and Q. M. were involved in the experimental design and statistical analyses. All authors contributed to the writing of the manuscript and agreed with the final content.
Compliance with Ethical Standards
All experimental procedures were approved by the Animal Management Committee (in charge of animal welfare) of the Institute of Animal Science, Chinese Academy of Agricultural Sciences (IAS-CAAS, Beijing, China) and performed in accordance with the guidelines. Ethical approval on animal survival was given by the Animal Ethics Committee of IAS-CAAS.
Conflict of Interest
The authors declare that they have no conflict of interest.
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