Investigation of the Effect of Heat Stress on Egg Quality in Laying Hens

The thermoregulatory capacity of poultry kept in high-temperature environments is significantly impaired; heat stress can negatively affect their productive performance and health, leading to death. This study was aimed to determine the effect of high temperature on egg quality traits and the applicability of Brix refractometry in measuring total serum protein in eggs. A total of 24 Lohman Brown laying hens (12 control/12 heat stress) aged 30 weeks were used in the study. Laying hens were housed individually in an area of 1350 cm2. The experiment began one week after the laying hens were placed in the cages and lasted a total of four weeks. The room temperature in the control group was maintained at 24±2 °C (24 hours); the room temperature in the heat stress group was kept at 35±2 °C (09:00-17:00). The results showed that egg weight (g) decreased in the heat stress group (p=0.001). Additionally, it was determined that eggshell thickness (mm) significantly decreased in the stress-applied group (p=0.002). Similarly, egg yolk height (mm) was found to be significantly lower in the heat stress group (p=0.002); in contrast, the incidence of blood and meat spots in the eggs was found to be higher (p=0.01). These findings suggest that heat stress negatively affects various internal and external egg quality parameters. Moreover while the Brix refractometer appeared to offer a practical quick approach for estimating egg serum total protein it revealed no statistically significant differences. Therefore, while its use appears promising, further studies are needed to confirm its reliability under different physiological conditions.