The present study was designed to study the change of shell quality, shell strength, hatching output, calcium (ca) and phosphorus (ph) concentrations in tibia bone for embryos and hatched chicks, bone strength and some related physiological parameters as affected by either chicken strain (Mandarah, M and Gimmizah, G) or osteopontin (OPN) protein in eggshell. Results indicated that M strain surpassed (p≤0.05) G one for OPN concentration (ng/ μL) in eggshell of fresh eggs, eggshell at hatch, tibia for hatched chicks besides in hatched chick's blood. Egg quality including eggshell weight %,shell index, shell strength (Newton), eggshell and eggshell membranes thickness (mm) were significantly increased for M strain compared with those for G one, whereas egg abnormalities % and egg weights were significantly (p≤0.05) increased for G chickens. Moreover, egg weight loss % during incubation, embryonic mortality %, hatch time (h) and hatch window (h) were significantly diminished for eggs produced from M chickens compared to those for G one besides, M strain had the higher percentage of hatchability of fertile eggs (p≤0.05). Mandarah chickens represented significant increase of ca and ph concentrations compared with G ones in fresh eggs and eggshell for embryos at days 9 and 15. Mandarah chicks surpassed (p≤0.05) G ones with respect to plasma ca, ph and parathyroid hormone. Also, tibia bones for embryos at day 15 and hatched chicks were stronger (p≤0.05) for M strain than those for G one.
The important role of the genes due to chicken strain besides OPN protein in eggshell and embryonic bone could open promising tool for understanding the quality of eggshell and its applications for breeding programs.