Low-dose ozone application during storage modulates yolk oxidation and enhances hatchability in broiler hatching eggs

This study evaluated whether low-dose ozone exposure during storage can mitigate the negative effects of long-term storage on egg quality, yolk oxidative status, and hatching outcomes in broiler hatching eggs. A total of 1,350 eggs from 67-wk-old Ross 308 breeders were allocated to a 2 × 3 factorial arrangement of treatments: storage for 0 or 14 d and daily exposure to 0, 4, or 7 ppm ozone for 30 min. Egg quality traits (albumen index, yolk index, Haugh unit, shell thickness and ratios), eggshell microbial load (log10 CFU/mL), yolk malondialdehyde (MDA; nmol/mg protein), yolk protein content (mg/mL), and hatchability and embryonic mortality were recorded. Data were analyzed by two-way ANOVA with storage time and ozone dose as fixed effects. Fourteen days of storage reduced albumen index, yolk index, and Haugh unit and increased yolk MDA (5.70 vs. 8.87 nmol/mg protein; P < 0.001) and protein content (14.34 vs. 15.24 mg/mL; P  < 0.01). Ozone markedly reduced eggshell microbial load in non-stored and stored eggs (eg in stored eggs, 9.14, 3.69, and 1.77 log10 CFU/mL at 0, 4, and 7 ppm; P  = 0.001). Yolk MDA was greater at 7 ppm than at 0 or 4 ppm at both storage times (P  ≤ 0.002), whereas 4 ppm did not differ from 0 ppm. For eggs stored, 0 d, 4 ppm increased hatchability of fertile eggs (96.42%) compared with 0 ppm (91.07%; P  = 0.034). After 14 d of storage, 4 ppm resulted in greater hatchability of fertile eggs than 7 ppm (92.92 vs. 80.39%; P  = 0.025), whereas values for the 0 ppm group (86.45%) were intermediate and did not differ from either group; 4 ppm also reduced early embryonic mortality compared with 7 ppm (2.65 vs. 11.76%; P  = 0.007). In conclusion, low-dose ozone (4 ppm) applied during storage reduced eggshell microbial load and supported embryonic viability and hatchability without increasing yolk lipid peroxidation, whereas higher ozone (7 ppm) increased yolk MDA and early embryonic loss in long-stored eggs.