The characteristics of broiler hatching eggs have the potential to effect broiler posthatch growth and processing yield. The association of set egg weight (SEW), length of incubation (LI), and mean daily percentage of incubational weight loss (MDPEWL) of embryonated Ross × Ross 708 broiler hatching eggs with subsequent posthatch BW and processing yield was investigated. Sixty Ross × Ross 708 broiler hatching eggs were randomly set on each of 8 replicate tray levels of an incubator. Weight loss of individual embryonated eggs between 0 and 10.5, 10.5 and 18.5, and 0 and 18.5 d of incubation was determined for the calculation of MDPEWL. Furthermore, on 18.5 d of incubation, embryonated eggs were transferred to a hatcher unit where they were individually monitored for hatch every 12 h for determination of LI. Chicks were placed in corresponding replicate floor pens and were grown out from 0 (21.5 d of incubation) to 49 d posthatch. Live bird BW as a percentage of SEW on 21.0 d of incubation and d 0 and 49 posthatch, and bird sex on d 49 posthatch were determined. After commercial processing, carcass weight as a percentage of SEW, and carcass, abdominal fat pad, wings, breast muscle, tenders, drumsticks, and thighs weights as percentages of live BW were determined. Bird BW on 21.0 d of incubation and on d 0 and 49 posthatch were positively correlated or interrelated with SEW. Between 0 and 10.5 d of incubation, MDPEWL was negatively correlated with absolute and relative BW on 21.0 d of incubation, absolute BW on d 0 posthatch, and relative tenders weight. Further, LI was positively correlated with absolute and relative BW on 21.0 d of incubation and d 0 posthatch, but was negatively correlated with relative (percentage of live BW) carcass weight on d 49 posthatch. The MDPEWL of modern strain broiler hatching eggs should be closely monitored, particularly during the first half of incubation, for the regulation of LI and hatchling BW and for their potential effects on processing yield characteristics.
