Gravidade específica como um fator importante na eclodibilidade e sua associação com minerais e metabólitos da gema em matrizes poedeiras brancas

Abstract

This work was divided into two chapters. The first presents a literature review addressing the importance of egg quality for embryonic mortality and the role of minerals and metabolites present in the yolk. The second chapter consists of an original research article evaluating whether egg geometry, weight loss, and specific gravity (SG) affect hatchability, as well as whether yolk mineral and metabolite profiles are associated with eggshell density. Before hatch, we identified the most effective methods for measuring specific gravity and egg geometry to ensure precise results. In total, 8,874 eggs from five flocks of Lohmann LSL Lite breeders aged 52 to 64 weeks were analyzed. Specific gravity was determined using Archimedes’ principle, which showed higher agreement and lower systematic bias than the salt-solution flotation method, while egg geometry was obtained through digital image analysis. Although egg shape index and weight loss influenced hatchability, SG provided the most consistent results. Eggs in the upper 50% of the SG quartiles exhibited higher hatchability than those in the lower 50%, primarily due to lower infertility rates and reduced early embryonic mortality. Regarding fertility, we evaluated minerals and metabolites in yolks from eggs with low and high SG. Mineral concentrations isolated, did not differ significantly between SG groups. While the yolk Na:K ratio showed a positive but weak association with the SG, it indicates that mineral composition alone explains little of the variation in eggshell density. Metabolomic analysis revealed lower levels of melatonin glucuronide and higher levels of dihydroxytetradecanoic acid in high-SG eggs compared with low-SG eggs. Based on a large dataset, this study demonstrates that eggs with low specific gravity show reduced hatchability due to infertility and early embryonic mortality. We further identified that the Na:K ratio, melatonin glucuronide, and dihydroxytetradecanoic acid in the yolk may serve as potential biomarkers of specific gravity, offering new perspectives for future research on the relationship between fertility and SG.