Relationship between pre-incubation egg parameters and chick weight after hatching in layer breeds

The aim of the study was to define the egg parameters, which could be measured on an intact egg prior to incubation, to accurately predict chick weight after hatching. The eggs from laying hens of the White Leghorn, Rhode Island White and Rhode Island Red parent stocks were investigated. The results showed that egg volume (coefficient of variation CV = 6.9%) and weight (CV = 6.2%) were the most variable egg parameters as compared with less variable egg surface area (CV = 4.5%) and density (CV = 3.1%). There was no significant inter-strain difference in egg weight. Other egg parameters such as volume, shell surface area, density, and egg-chick weight ratios differed significantly. Chick weights differed significantly only between the White Leghorn and Rhode Island White lines. Egg density was chosen as an indirect indicator of shell thickness and/or shell density, but the correlation between chick weight and egg density was too small (correlation coefficient R = 0.02) to state that shell parameters influence much chick weight. Egg weight alone had the biggest correlation with chick weight (R = 0.56) in comparison with egg volume (R = 0.50) and surface area (R = 0.50) for the combined data across three strains. The accuracy of the results of chick weights predicted by the proposed mathematical equations and expressed in terms of coefficient of determination R-2 varied from 0.250 to 0.615, depending on the strain data and the type of the predictive formula. The best prediction was obtained for the quadratic type of the equation when three basic egg parameters (weight, volume and surface area) were considered. (C) 2002 Silsoe Research Institute. Published by Elsevier Science Ltd. All rights reserved.