Effect of intermittent thermal stimulation on hatchability and physicochemical properties of duck eggs

The study aimed to evaluate the effects of intermittent thermal stimulation during short-term egg storage (72 hours) on egg quality, hatching performance, hatching dynamics, duckling quality, and changes in the physicochemical properties of egg components during incubation. A total of 890 hatching eggs from Cherry Valley ducks were used. Following the assessment of egg quality before storage, the eggs were either stored at ≤15°C without thermal stimulation (N-TS) or subjected to two 8-h heating periods at 37.7°C and 55% relative humidity, separated by 8-h cooling periods at ≤15°C (TS). After storage, the eggs were incubated under standard conditions. Egg quality and egg weight loss were evaluated, whereas lysozyme activity, viscosity, pH, and mineral composition were determined before incubation and on d 7 and 14 of incubation. Eggs from the TS group had higher thick albumen height (P=0.018) and a higher albumen index (P=0.021), but a lower yolk index (P=0.041) and higher weight loss during storage (P<0.001) than eggs from the N-TS group. Hatchability of set eggs and fertile eggs, embryonic mortality, and Pasgar scores did not differ between the groups (P>0.05). However, thermal stimulation markedly accelerated the hatching process, as 72.24% of healthy ducklings in the TS group had hatched by 616 h of incubation, compared with only 10.41% in the N-TS group (P<0.001). Relative duckling weight was lower in the TS group (P=0.005). Thermal stimulation increased lysozyme activity in the amniotic fluid on d 14 of incubation (P=0.039). Transient differences in viscosity, pH, and the concentrations of selected mineral elements were also observed. These findings indicate that intermittent thermal stimulation during short-term storage modified the physicochemical environment of duck eggs and accelerated hatching, but did not improve final hatchability.