In ovo sericin suppresses hepatic DNA demethylation in broilers at hatch

Abstract

Over the years, the rearing period of the commercial broilers to attain the slaughter weight has reduced significantly. Hence, it emphasizes the importance of the period of embryonic development. It has been shown that inadequate nutritional supply to the embryo at the later phases can lead to various abnormalities. This adversely affects the hatchability and further the post-hatch performance of the chicks. This study attempted to study the effect of in ovo feeding of sericin on the developing Ross-308 embryos. Fertile eggs (n = 210) at 17.5 days of embryonic development (ED) were equally divided into five treatments based on the concentration of sericin fed. The treatments were: uninjected control (UCON), followed by different concentrations of sericin injected groups as 0SER (0 % sericin), 1.5SER (1.5 % sericin), 3.0SER (3.0 % sericin), and 4.5SER (4.5 % sericin). Hatch parameters across treatments did not differ significantly. Similarly, the organ (liver, yolk sac, gizzard, proventriculus and heart) indices and plasma antioxidant markers such as 2,2-Diphenyl-1-picrylhydrazyl - radical scavenging activity % (DPPH-RSA%) and malondialdehyde (MDA) content did not differ significantly across treatments. The hepatic mRNA expression of superoxide dismutase (SOD) was higher in 3.0SER treatment in comparison to 4.5SER. On the other hand, in ovo sericin downregulated the hepatic gene expression of DNA demethylation-related enzymes such as ten-eleven translocation methylcytosine dioxygenase 3 (TET3, p = 0.028) and methyl-CpG-binding domain protein 4 (MBD4, p = 0.007) compared to 0SER. Pearson's correlation analyses revealed a significant correlation between the hepatic gene expression of NADPH oxidase (NOX) related genes and DNA-demethylation-related genes (p < 0.01). Hence, in ovo sericin might not be potentially beneficial in improving the hatchability of broilers. Also, no notable effects on the antioxidant capacity of plasma was recorded. However, in ovo sericin downregulated the mRNA expression of some DNA demethylation-related genes which were significantly correlated with the expression of NOXs. Therefore, in ovo sericin feeding could suppress DNA demethylation which could in turn be beneficial to alleviate oxidative stress at hatch.