Researches Regarding the Genetic Determinism of the Growth Process in a Large Hen Line

Genetic determinism study presents a great importance due to the fact that all the characters linked to the growth process depend upon some specific genes action, gene which with their summative effect establishes the phenotypic manifestation of the mentioned characters. To emphasize the genetic determinism of a character it is necessary the estimation of the genetic parameters, the main important ones being: causal compounds of variance,heritability, genotypic correlations. Heritability coefficients represent a property not only of a character, but of a population and the environment that population lives in. The aim of the researches was the study of the genetic determinism of the growth and development process in a large hen line, for two characters: body weight and breast muscle at 7 weeks old, separately by gender. The researches were carried out in Avicola Bucharest S.A. on individuals in Plymouth Rock 010 maternal line. The studied individuals owed to 40 half-sib families, respective 384 full-sib families, on a total number of 2332 males and 2462 females. To establish the causal compounds of variance it was used the statistic model with three variation sources, which leads to the genetic parameters establishing. To estimate the values of the phenotypic correlations it started from their basic formulas and there were introduced the values of the phenotypic variances and covariance. It was established the value of the genotypic correlations using the values of inter familial variance and covariance. It is necessary to know the phenotypic, genotypic and environmental correlations between the two studied characters to establish a correct selection base, having in view the simultaneous improvement of those. The values of the heritability coefficients for body weight in males (h2=0,18) and in females(h2=0,13) shows a stronger genetic determinism comparatively the small lines, so lower values comparatively other authors who studied this character. The values of the heritability coefficients for breast muscle was higher in males (h2=0,15) than in females(h2=0,04). By the whole, the two characters present very lowphenotypic, genotypic and environmental correlations in half-sib families.