Environmental effects and genotype-environment interactions in laying stocks of chickens

Data collected during the Eighth, Ninth, Tenth, Eleventh and Twelfth Tennessee Random Sample Laying Tests (1964 to 1969) were analyzed statistically using analysis of variance. Egg production, egg size distribution, egg quality and feed efficiency variables were calculated on a yearly and quarterly basis. The effects: strains (20 strains), years (3 years), density level (1 per cage and 2 per cage), protein level (13 and 17 percent), insulation value (4R and 13R), quarters (four quarters) and their interactions were tested for statistical significance. Strains were found to differ significantly with respect to nearly all traits studied. Strain density and strain protein interactions were found for many variables. Differences between quarters were significant as would be expected for the traits studied. The other main effects, years, insulation value, protein level and density level were not consistently significant. Many of the strain environment interactions were found to be significant. More strain environment interactions were detectable as statistically significant when quarterly records, instead of year records, were used as a basis for analysis. Several of the second order interactions also were found to be significant. These data indicate that strain environment interactions are real, are difficult to detect and require experimental procedures which allow for detection of small differences if statistical significance is to be shown. Sub samples of egg production strains entered in the Eighth, Ninth, Tenth, Eleventh and Twelfth Random Sample Laying Test did not perform equally within a strain when subjected to different environments.