Interactive Influences of Maternal Derived Testosterone, Egg Weight and Yolk Index on Corticosterone Concentration and Yolk Structural Integrity

Testosterone, a hormone deposited into the egg yolk related to yolk quality, plays a crucial role in embryo development during embryogenesis. This study aimed to investigate the interactive effects of maternal derived testosterone, yolk index, and egg weight on yolk corticosterone hormone concentration and yolk quality traits of hatching eggs obtained from broiler breeder hens. Eggs were classified according to maternal testosterone level (low or high), yolk index value (low or high), and as light or heavy on the mean egg weight (EW). Yolk corticosterone concentration and yolk quality characteristics were measured. The significant negative correlations were observed between egg yolk testosterone and corticosterone concentration (r=-0.350; P=0.023), and between egg yolk testosterone and yolk index (r=-0.340; P=0.029). Egg weight was positively correlated with yolk index (r=0.399; P=0.004), yolk height (r=0.522; P=0.005), and yolk weight (r=0.491; P=0.003), whereas relative yolk weight was negatively correlated with EW (r=-0.399; P=0.010). Maternal testosterone (MT) significantly affected corticostetone concentration in the egg yolk (P=0.006). The high MT group demonstrated lower corticosterone level in the egg yolk. The significant interactions were detected between MT and yolk index (YI) (P=0.004), and among MT, YI, and EW (P=0.023) for yolk corticosterone concentrations. In contrast, yolk quality traits were mainly influenced by EW and YI (P<0.05) rather than MT (P>0.05). The results indicated that MT plays a central role in regulating corticosterone accumulation in egg yolk, while hatching egg weight and yolk index primarily determine yolk quality characteristics. In conclusion, maternal derived hormone allocation to the yolk is closely linked to maternal’ hormonal status and structural integrity of egg yolk.