Field study on the factors affecting egg weight loss, early embryonic mortality, hatchability, and chick mortality with the use of classification tree technique.

The aim of this research was to study the factors affecting hatchability, percentage of egg weight loss during incubation, early embryonic mortality, and chick mortality in the first seven days of life in the field. This study was performed on 20,817,600 hatching eggs originating from 7 different breeder flocks. The factors responsible for variability of investigated traits were the following: genotype (ROSS 308, ROSS PM3), hen age (25 to 30, 31 to 45, 46 to 50, and 51 to 60 wk), egg storage time (0 to 13 d), and setter and hatcher type (Digital, Airstreamer, Vision, Focus, Biostreamer), which were determined using the classification tree technique. Statistical calculations were performed using R software, version 3.4.3. Moreover, 2-way analysis of variance followed by Duncan's multiple comparison test was performed. The breeder flock age and egg storage time were the most important factors responsible for variability in the percentage of fertile hatchability; however, setter and hatcher type also affected the level of this trait. The highest hatchability was observed for eggs laid by hens aged 31 to 50 wk and stored up to 6 d. Genotype was the most important determinant of the percentage of egg weight loss and that Ross 308 eggs lose less weight when compared to Ross PM3 ones. Egg storage time was the most important factor, which affected early embryonic mortality. The present study has shown that the 2 main factors, i.e., breeder flock age and egg storage time, that affected hatchability have also influenced chick mortality. Moreover, it was found that both hatcher and setter type affected chick mortality in the first 7 d of life. The importance of this research lies in the fact that besides showing the most important factors affecting hatching process, we were also able to suggest how to adjust the management decisions at commercial hatcheries in order to increase production results in different egg sets, which vary in respect of breeder flock age, egg storage time, setter, and hatcher type and genotype.