Effects of embryo temperature estimation methodology on the determination of eggshell conductance values in Ross 708 broiler hatching eggs with consideration given to eggshell pigmentation variation

In a preliminary experiment, the influence of pigment color variation on the temperature readings of the shells (EST) of live embryonated Ross 708 broiler hatching eggs was tested. Prior to set, eggshell color in L*, a*, and b* coordinates were measured at the equator of each egg. Eggshell pigmentation was found not to influence EST from zero through 18 d of incubation (DOI). In a subsequent experiment, EST, as well as air cell (ACT) and cloaca (CLT) temperature measurements were used for the calculation of absolute (GH2O) and specific (gH20) eggshell conductance values for these same types of eggs. An infrared thermometer was used to determine EST from zero to 19 DOI, ACT was measured using a transponder from 12 to 19 DOI, and CLT was determined using a transponder at 4:00 PM at 19 DOI. In the 12 to 19 DOI interval, the values for GH2O as well as for gH20 that were calculated using either EST or ACT were significantly correlated (r ≥ 0.99; P < 0.0001). A similar correlation level for both GH2O and gH20 was likewise observed in the 10:00 AM to 10:00 PM time period at 19 DOI when either EST, ACT, or CLT was used. However, in the 12 to 19 DOI interval, calculated GH2O and gH20 values based on ACT were significantly different from those based on EST. In addition, a significant difference in calculated GH2O and gH20 values resulted when ACT was used rather than when EST or CLT was used in the 10:00 AM to 10:00 PM time period at 19 DOI. In both time periods, GH2O and gH20 values calculated using ACT were significantly lower than those derived using the other 2 types of measurements. These findings suggest that although EST was not affected by shell coloration, because ACT more closely reflects embryo body temperature, it should be used to more accurately calculate the GH2O and gH20 of Ross 708 broiler hatching eggs.