Interactive effects of early in ovo feeding and incubation temperature on egg quality traits and embryonic...

Embryonic growth and nutrient utilization during incubation are influenced by both thermal conditions and nutrient availability; however, information on the combined effects of in ovo nutrient supplementation and incubation temperature on embryonic development remains limited. This study investigated the interactive effects of early in ovo feeding and incubation temperature on egg quality traits and embryonic development in broiler breeder eggs. A total of 270 fertile eggs were randomly assigned to a 3 × 3 factorial arrangement comprising three in ovo treatments (phosphate-buffered saline (PBS; control), glucose, and vitamin D₃) and three constant incubation temperatures (36.5°C, 37.0°C, and 37.5°C), with three replicates of 10 eggs per treatment combination. On embryonic day (ED) 10, the eggs were injected with 0.2 mL PBS, glucose solution (5 mg/mL), or vitamin D₃ solution (25 mg/mL). The egg and embryo measurements were recorded daily from ED15 to ED20. Significant in ovo treatment × incubation temperature interactions (p < 0.05) were observed for several developmental traits. The egg weight was affected only on ED18, while eggshell thickness was influenced on ED15 and ED17-20. In addition, wet embryo weight showed interaction effects on ED15 and ED17-20, whereas femur length was affected on ED15 and ED17, and tibia length on ED16, ED17, and ED19. The results showed that eggshell temperature was influenced on most incubation days except ED16. Wet residual yolk sac weight exhibited an interaction effect only on ED19, while dry residual yolk sac weight was affected from ED17 to ED20 (p < 0.05). Incubation temperature significantly influenced embryonic development, with embryos incubated at 37.0°C generally exhibiting lower dry embryo weight and shorter embryo length than those incubated at 36.5°C and 37.5°C. Glucose supplementation increased dry embryo weight on selected days, whereas vitamin D₃ supplementation enhanced embryonic growth, particularly at 36.5°C. Taken together, embryonic responses to nutrient supplementation were temperature-dependent, with vitamin D₃-injected eggs incubated at 36.5°C showing the greatest growth and skeletal development, while embryos incubated at 37.0°C exhibited the poorest growth performance.