Changes in fatty acid and mineral profiles of the turkey egg yolk-yolk sac complex during embryonic development

The yolk-yolk sac complex is the main nutrient source for the avian embryo and undergoes marked compositional changes during incubation. However, information on mineral and fatty acid dynamics in turkey eggs remains limited. This study evaluated changes in mineral concentrations, absolute mineral contents, and fatty acid composition of the turkey egg yolk-yolk sac complex during embryonic development. A total of 200 fertile eggs from 56-week-old native turkey breeders were incubated under standard conditions. Samples were collected at days 0, 8.5, 18.5, 23.5, and 28 of incubation. For each time point, six pooled replicates were prepared, each obtained from five eggs. Mineral concentrations and absolute contents were determined by ICP-OES, whereas fatty acid methyl esters were analysed by GC-FID and expressed as percentages of total identified fatty acids. Incubation time significantly affected the concentrations of Ca, Cu, Fe, K, Na, P, Sr, and Zn, while Mg and Mn concentrations were not affected. Calcium and Sr concentrations increased toward hatch, whereas P concentration decreased markedly. Absolute mineral contents showed distinct patterns: Ca increased after an initial decrease at day 8.5, Sr peaked at day 23.5, and P, Fe, K, Na, Cu, and Zn generally declined by hatch. The relative fatty acid profile was also affected by incubation time. Palmitic and oleic acids were the predominant fatty acids throughout incubation. At hatch, myristic, palmitic, and linoleic acids represented greater proportions of the residual fatty acid pool, whereas the relative proportions of oleic and arachidonic acids were lower. These results indicate that the turkey yolk-yolk sac complex is dynamically remodeled during embryogenesis, reflecting mineral mobilization and changes in the relative availability of fatty acids before hatch.