The effects of genotype and environment on traits and their correlations in layers

Data collected during the nineteenth Tennessee Random Sample Laying Test (1975-1976) were analyzed and studied. Two kinds of analysis of the data were used.

The first was the analysis of variance based on a factorial arrangement of stocks and the four kinds of treatments in order to determine the existence of differences among stock and treatments and of interactions. Stocks were found to be significantly different from each other with respect to the various production traits.

Treatments were found to be significantly different with respect to certain production traits. Vitamin A significantly (P<0.05) increased the percent of large size eggs and Haugh units, while vitamin C significantly (P<0.01) increased the percent of medium size eggs. However, Protamone significantly (P<0.01) increased the percent of medium eggs, reduced (P<0.001) body weight and increased (P<0.05) Haugh units.

No significant interactions between stocks and treatments were found with respect to the various production traits.

Coefficients of correlation among production variables for each stock and treatment were computed. The sign and magnitude of the relationship between the traits showed great variation from treatment to treatment and from stock to stock.

The best multiple linear regression equations for the prediction of the various traits were constructed and yielded coefficients of determination ranging from 0.77 for prediction of variables, especially in cases involving correlation which reflect part-whole automaticity.