Abstract
The aim of the study was to investigate eggshell traits; including eggshell water vapor conductance, eggshell thickness, pore density, egg weight loss as well as eggshell surface area and volume in 28 and 40 week-old broiler breeders. Furthermore, the phenotypic correlations among the eggshell characteristics were determined. The eggs were ranged from 54.41 g to 60.78 g and 54.71 g to 60.62 g in 28 and 40 wk-old age groups, respectively. All eggs were weighed and numbered before setting and were monitored individually until the end of the incubation. Mean eggshell water vapor conductance (G) value was 11.00±1.01 mg H2O day-1 torr-1 in 28 wk-old flock and 11.99±1.28 mg H2O day-1 torr-1 in 40 wk-old flock respectively (P<0.05). The mean value of shell thickness and pore density mean along with the two regions (broad end and equator) were higher and significant in 28 wk-old flock (P<0.01). Egg weight loss was not found to be significant. Surface area was higher in 40 wk-old flock while as volume was higher in 28 wk-old flocks (P<0.01). There was no correlation between eggshell thickness and pore density. Both eggshell thickness and pore density were having significant positive correlation along with three eggshell regions in each flock ages (P<0.01).
Highlights
Water vapor conductance is one of the important factors that influence the embryonic gas exchange and development of the embryo (Hamidu et al 2007)
It has been observed that eggs from older hens have higher eggshell water vapor conductance, this variation could have arisen from the difference of the breeder age (Roque & Soares 1994)
Two early embryonic deaths were determined in 28 wk flock, whereas one early embryonic death and two late embryonic deaths was found in 40 wk-old flock
Summary
Water vapor conductance is one of the important factors that influence the embryonic gas exchange and development of the embryo (Hamidu et al 2007). It determines the respiratory pattern of the egg that is influenced by eggshell properties including the number of pores and thickness of eggshell (Peebles & Brake 1987). To make an ideal gas exchange during the embryonic development, the conductance of eggshell should be considered as a functional tool besides other factors like a gaseous composition, barometric pressure of the surrounding natural air, the hatchery ventilation rate, humidity and embryonic oxygen uptake (Visschedijk 1991)
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