# Fatty acid composition in the yolk and yolk sac, embryo development, IGF-I and VEGF-A gene expressions and hatching results in eggs obtained from local and commercial breeders

## TL;DR

This study compares local and commercial chicken breeds to understand differences in egg development, gene expression, and hatching outcomes.

## Contribution

The study identifies genotype-specific differences in fatty acid composition, gene expression (IGF-I and VEGF-A), and hatching performance in local and commercial chicken breeds.

## Key findings

- Local breeds like Denizli showed distinct gene expression patterns compared to commercial hybrids.
- Broiler embryos had higher embryo weights, while local breeds retained more residual yolk sac weight.
- Hybrid breeds exhibited higher fertility and hatchability compared to local breeds.

## Abstract

This study investigated fatty acid composition in yolk and yolk sac, embryo development, IGF-I and VEGF-A gene expressions, and hatching results in eggs from local (Denizli and Gerze) and commercial (broiler (ROSS-308 and layer (Hy-Line W-80) breeders. A total of 1032 eggs per genotype were incubated. Eggs were weighed, numbered, and sampled at the beginning and on days 10, 13, 16, and 19 for yolk, embryo, fatty acid, and gene expression analyses. At hatch, all chicks were weighed, and eight per genotype were sampled for fatty acid composition in the residual yolk sac and gene expression in breast muscle. Significant genotypic differences were found in egg and chick weights, with layer hybrids having the greatest (59.68 and 41.13 g, respectively) and Gerze the lowest values (52.22 and 36.40 g, respectively). Relative embryo weights increased during incubation, with broilers showing the greatest values and local breeds having higher residual yolk sac weights. While chick weights differed, relative chick weights did not vary significantly. Fertility, embryonic mortality, and hatchability were affected by genotype; hybrids had higher fertility and hatchability, whereas Gerze showed the greatest embryonic mortality and lowest hatchability (11.23 and 67.76%, respectively). Fatty acid profiles showed palmitic (approximately 24–25%) and stearic acids (approximately 9–10%) as dominant saturated fatty acids, oleic acid (approximately 40–45%) as the main MUFA, and linoleic acid (approximately 15–20%) as the major PUFA. In terms of the IGF-1 gene, embryos of the Denizli breed were downregulated by 0.38 fold compared to laying hybrids while in chicks this change was found to be an 8.66 fold upregulation. It was determined that these values were downregulated by 0.08 fold in embryos and 0. 71 fold in chicks in terms of the VGEFA gene. PPI analysis of 32 IGF1/VEGFA interactors revealed a core module centered on FGFs, PGF, neuropilins, and VEGF receptors. Enrichment pointed to system development and angiogenesis, with MAPK, receptor tyrosinekinase, IGF1RIRS, and calcium signaling as key pathways. Genotypespecific differences in this signaling hub underscore the value of local breeds like Denizli for optimizing embryonic vascular and muscle development in sustainable poultry production.