author(s)
Shaista Saeedatu Nissa, IU Sheikh, MT Banday, Bushra Zaffer, Shehrish Shafiq, Azra Chishti and Asma Irshad Qureshi

abstract
A study was conducted to investigate the effect of different light sources viz. Incandescent, CFL and LED on the stress level of broiler chicken. One hundred and sixty day old broiler chicks were brooded in battery cages for a week and then distributed randomly into four light treatment group’s viz., Natural light (T₁) as Control, Incandescent (T₂), CFL (T₃) and LED (T4) groups having 40 chicks in each which were again subdivided into four replicates of 10 chicks each. The stress levels were estimated by measuring the plasma corticosterone levels and heterophil lymphocyte ratio (H:L) in the blood at second, third and fifth week. The plasma corticosterone level was found to be highest during 2^nd week in birds reared under INC light (11.07^c ± 0.39) and lowest in 5^th week under LED light (5.17^a ±0.22).The results showed that heterophil: lymphocyte (H:L) ratio and levels of plasma corticosterone were significantly (P≤0.05) higher in the INC group and lowest in the LED group.