Abstract
The present experiment was carried out for determining the role of osteopontin protein (OPN) in eggshell on shell quality and consequent effect on skeletal embryos, hatching traits and some physiological parameters besides its relation with two stages of laying cycle of Mandarah chickens (32 to42 vs 52 to 62 wks. of age). The obtained results are summarized as follows:- Osteopontin concentrations (ng/µL) were decreased (P≤0.05) for eggshell of fresh eggs and hatched chicks for eggs produced from elder chickens compared with those from younger ones. The same trend of significant decrease of OPN was observed for tibia of hatched chicks and for chick's blood. Osteopontin concentration decreased (P≤0.05) with the increase of embryonic age with respect to eggshell whereas, it increased for tibia. Younger chickens represented significant increase of eggshell strength, eggshell index, eggshell and eggshell membranes thickness compared to those for elder ones. Embryonic mortality %, hatch time (hr) and chick body weight at pull out (g) were significantly increased for eggs produced from elder chickens compared to those for younger ones while, hatchability of fertile eggs % was significantly decreased. Calcium and phosphorus values were significantly decreased with the increase of flock age for eggshell of fresh eggs and eggshell through different times of incubation besides tibia of embryos at 15th day and for chicks at hatch. Blood constituents of hatched chicks as calcium, phosphorus, and parathyroid hormone were significantly decreased with the increase of chicken age. Relative asymmetry is higher (P≤0.05) for wing, tibia, tarsus and femur lengths of embryos and baby chicks for younger flock compared to elder one except that for tarsus of baby chicks. The contributions of OPN as a major protein in shell structure and subsequent effects on hatching process are proven and this conclusion could set up alternative tool for eggshell quality evaluation and breeding selection programs.
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