A total of 400 females and 400 males of Mandarah strain at 6 weeks old were transferred to an environmentally controlled light proof house. The controlled house are divided inside into four separate partition. They were distributed to the partitions according to the photoperiod regimen, since female chicks were placed in the first and third partition, while the males were placed in the second and fourth partition (200 chicks / partition with two sources of iodine (organic, inorganic ) inside each source two levels (0 .5 , 2 ) with 5 replicate for each treatment with 10 chicks in each replicate). Chicks in the first and second partition exposed toStep-up photoperiod (SUP):The photoperiod was increased gradually from 10 h/d at 8 weeks by half an hour each wk to reach 16-h/d at 20 wk of age. While, the chicks in the third and fourth partition exposed to Constant step-up photoperiod (CSUP): 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 . Chicks in each lighting regimen are divided equally into four groups ( 50 birds with 5 replicate) to receive one of the following dietary experiment : basal diet supplemented with 0 .5 (T1), 2 (T2) mg inorganic iodine (Potassium iodide) / Kg diet , 0 .5 (T3) , 2 (T4) mg organic iodine (I-enriched yeast) / Kg diet. Results showed that SUP regimen (Lr1) increased (P≤0.05) egg weight,eggshell thickness,haugh units, iodine content in egg yolk , semen quality, fertility, hatchability (%), chick quality traits, corticosterone and testosterone hormones compared with CSUP (Lr2). Also, organic iodine enhanced (P≤0.05) egg weight,eggshell thickness,haugh units, iodine content in egg yolk , semen quality, fertility, hatchability (%), chick quality traits, T3,T3/T4 ratio, corticosterone and testosterone hormones compared with inorganic iodine. Moreover, 2mg iodine/kg diet increased (P≤0.05) iodine content in egg yolk , thyroid hormones and decreased concentration of corticosterone hormone. In conclusion, providing SUP regimens for closed houses from 8-20 weeks birds age with 2mg organic iodine/kg diet could increased egg quality traits, the iodine content of yolk eggs, semen quality, chick quality traits, thyroid, corticosterone and testosterone hormones .
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 toStep-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.
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