EFFECT OF LIGHTING REGIMENS,LEVELS AND SOURCES OF DIETARY IODINE ON SEMEN QUALITY, YOLK IODINE CONTENT AND CHICKS QUALITY TRAITS OF MANDARAH CHICKENS STRAIN

Abstract

: 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 to Step-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 .