The effectiveness of selection for egg mass variability as a means of increasing phenotypic consolidation of the factory line of meat-egg chickens

Abstract

Goal. To evaluate the effectiveness of a new selection criterion, taking into account the variability of egg weight, to increase the level of phenotypic consolidation of the factory line of meat-egg chickens. Methods. The study was conducted during 2024-2025 based on the experimental farm “Preservation of the state gene pool of poultry” of the State Experimental Poultry Station of the Institute of Animal Husbandry of the NAAS on meat-egg chickens of the factory G2 line of the breed Plimutrok white of the Ukrainian breeding. Parental groups were formed according to two selection options — traditional (egg bearing at 40 weeks of life, and egg weight at the age of 30 weeks), and new (with additional consideration of intra-family variability in egg weight). Reproduction of the next generation was carried out, and coefficients of variation, indicators of consolidation, reproductive qualities, and productivity of descendants were analyzed. All indicators were determined according to generally accepted methods: live weight — individual weighing; the age of the beginning of bearing — the first laid eggs; egg-bearing capacity — the daily individual accounting of laid eggs; weight of eggs — weighing three daily collections; variability of egg weight — by coefficient of variation (CV); preservation — as a percentage of livestock at the end of the period to the initial one. The level of phenotypic consolidation of groups was determined by the method of evaluating the relative narrowing of intragroup variability. Statistical processing was performed by variational statistics using Microsoft Excel 2010; the validity of the intergroup differences was assessed by Student’s t-criterion (p ≤ 0.05). Results. In the group of chickens selected according to the new criterion (variability in egg weight at 30 weeks of age), the average coefficient of variation was 6.2%, while in the base group it was 7.4%. This was accompanied by a higher level of phenotypic consolidation (15.09% versus 9.30% in the baseline group and 8.97% on average in the line) without deterioration of the main productive characteristics. Reproductive indicators were better in the more consolidated group by weight of eggs: egg hatchability — 89.4% (2.3% higher), brood of young stock — 75.2% (versus 74.0%). The structure of the distribution of families showed an increase in the proportion of families with a low level of variability, and the correlation analysis confirmed the relative independence of this indicator from the main productive characteristics. In the next generation, the positive effect of selection remained: the share of stable families and the level of consolidation increased without reducing egg production. Conclusions. The use of intra-family variability of egg weight as an additional selection criterion made it possible to increase the homogeneity of the population while maintaining the main productive qualities. The use of a new criterion for selection in the parent generation made it possible to increase the level of phenotypic consolidation of the line in the next generation by 2.3% and contributed to increasing the number of families with a low level of variability in egg weight from 48.4% to 53.4%. The obtained results confirmed the effectiveness of the new selection method for targeted selection of the factory line of meat-eating chickens for consolidation by egg weight.