Abstract
Background
The present study aimed to investigate the impact of light emitting diode (LED) green light alone or in combination with melatonin on behaviour related hormones regulation during incubation under normal and under hormonal stress conditions in breeder eggs. This study divided into 2 experiments: In the first experiment LED green light effect on different hormone during incubation under normal condition, on Hy-line brown (low aggressive phenotype) and Roman pink (high aggressive phenotype) were tested. Total 296 eggs of each strain divided into two groups: LED green light incubation and dark incubation (control), each containing four replicates (37 eggs/replicate). Second experiment conducted to detect LED green light effect alone or in combination with melatonin during incubation under hormonal stress conditions. Total 704 eggs of Roman pink were taken and divided into four groups, each consisting of 176 eggs. Each group was further divided into 2 subgroups, LED green light-regulated incubation and dark incubation with 88 eggs per subgroup having 4 replicates of 22 eggs each. The groups were as follows: corticosterone solution injection (CI), corticosterone + melatonin mixed solution injection (CMI), Phosphate buffer solution injection (PI), and no injection (UI).
Results
Results from the first experiment revealed the higher level of serotonin hormone (related to calmness of behaviour) and lower of corticosterone hormone (related to aggressive behaviour) in Hy-Line brown embryos compares to those of Roman pink embryos during dark incubation. The LED green light incubation significantly increased the level of 5-HT while decreasing the CORT level in Roman pink embryos indicating its regulatory effect on behaviour related hormones. Results of the second experiments showed that LED green light incubation alleviated the CORT-induced hyperactivity of plasma 5-HT in Roman pink embryos. Furthermore, Melatonin (MLT) injection and LED green light together reduced the hormonal stress caused by corticosterone injection in the eggs.
Conclusions
Overall, the LED green light regulatory incubation demonstrated a regulatory effect on hormones related to behaviour. Additionally, when coupled with MLT injection, it synergistically mitigated hormonal stress in the embryos. So, LED green light incubation emerged as novel sustainable system to reduce the aggressive behviour and improve the productivity of the poultry birds.