The objective of the present experiment was to examine the effect of  lighting regimens, iodine sources and levels and their interactions on productive performance, hatching traits, some biochemical blood parameters and thyroid hormones of Mandarah chickens. A total of 400 Mandarah chicks at 8 weeks of age were housed in closed system house and divided randomly into two equal groups (200 chicks / group). Chicks of the first group were exposed to Step-Up Photoperiod (SUP): The photoperiod was increased gradually from 10 h/d at 8 wks of age by half an hour each wk to reach 16 h/d at 20 wk of age (Lr1), Chicks of the second group were exposed to Constant–Step Up Photoperiod (C- SUP): The photoperiod was kept constant at 12 h/d at 8 weeks of age until 16 wk of age and increased gradually by an hour each wk to reach 16 h/d at 20 wk of age (Lr2). The chicks within each lighting regimen were divided equally into four dietary supplementations groups (5 replicates of 10 birds each) as follows: basal diet supplemented with 0 .5 mg Potassium iodide (control, T1), 2 mg Potassium iodide (T2), 0 .5 mg Iodide-enriched yeast (T3) and 2 mg Iodide-enriched yeast (T4) / Kg diet. The results during the laying period up to 36 wk have shown that exposing Mandarah chickens to Lr1 regimen significantly improved egg weight, egg production (%) , egg mass , feed conversion ratio, fertility (%), hatchability (%),body weight at hatch, yolk sac and fabricious gland (%) compared to Lr2 regimen. Moreover, plasma IgM, IgG, TAC, HDL, HDL/LDL ratio and T4 significantly increased for Lr1 compared with Lr2. Feeding Mandarah chickens on 2mg organic iodine/kg diet significantly improved the laying performance , feed conversion ratio, plasma IgM, HDL, HDL/LDL, T3/T4, L%, H%, H/L ratio compared with inorganic iodine either o.5 or 2 mg /kg diet. Also, the interaction of Lr1_˟ organic iodine _˟ 2 represented highest (p<0.05) values of egg production%,egg mass,plasma IgM, HDL,HDL/LDL,T3/T4 ratio and L (%), Besides improvement of feed conversion compared with other interactions.

In conclusion, it is possible to use the SUP regimen combined with feeding  on 2 mg organic iodine /kg diet in laying management from 8-36 weeks of age to improve productive and reproductive performance, hatching traits, hatched chicks body weight and immunity system of Mandarah chickens.