Parameters of plasticity and stability of laying hens under the interaction “genotype × environment”

Abstract

The article presents the research results on the evaluation of the polygenically determined quantitative trait “laying” under the influence of the interaction “genotype × environment” on the comprehensive genetic material of chickens. Meat and egg hens of the original maternal form of domestic breeding, descendants of the first and second generations of different genesis, and improved synthetic populations performed it. The laying hens of the experimental groups were determined during seven months of egg laying. By using a two-factor variance analysis, a probable influence of genotypic affiliation (P < 0.05) and the month of egg laying (P < 0.001) on the level of manifestation of laying hens of the studied groups was established. The probable difference in the gradation of “condition” factors made it possible to evaluate the parameters of plasticity and stability in the studied groups of birds. The regression coefficient (bi) characterizes the average reaction of a group of individuals to a change in environmental conditions, that is, their plasticity, which makes it possible to predict the variability of the trait under the studied conditions. High bi-indicators indicate a more significant response of a group of chickens to a change in environmental conditions, influenced by active factors. That is, the larger the value of bi, the steeper the regression line, and the more sensitive the group is to changes in detention conditions. A zero or close to zero value of bi indicates that the group reacts poorly to changes in environmental conditions (in our case, the months of egg-laying). Plasticity analysis makes it possible to identify genotypes of birds with significant adaptability to changes in environmental conditions. The laying hens of the created synthetic population, the offspring of the first generation of different genetic origins, and the F2 hens of the “K-51” group were more plastic in laying. This indicates the slightest response of this bird to changes in environmental conditions. The “Ross” birds of the “K-22” and “K-32” groups of different generations and the original maternal form F10 were less plastic according to this feature; that is, they were more sensitive to the influence of active factors. The variant of stability (S2i) of the feature shows how reliably the selection feature of the studied group of birds corresponds to the plasticity estimated by the regression coefficient. The closer the S2i indicators are to zero, the less the empirical values of the characteristic differ from the theoretical values located on the regression line. The “Ross” hens of the second generation of the “K-22” and “K-32” groups were distinguished by their high laying stability (S2i=2.42–2.65). The least stable in terms of this polygenic trait was the “Kobb” chickens of the “K-51” and “K-5” groups (S2i=6.01–9.53). Hybrids of the first generation were characterized by more excellent laying stability than mothers.