Strain differences with respect to economic traits of egg laying chickens entered in the Tennessee Random Sample Laying Test

Data collected during the Fifteenth Tennessee Random Sample Laying Test (1972) were analyzed statistically using analysis of variance and conventional product-movement coefficients of correlation among most variables studied to determine the magnitude of these correlations in both strain and treatment subclasses. The variables studied were egg production, average egg weight, feed efficiency, mortality, egg quality, income over chick and feed cost, body weight and sexual maturity. The effects assessed were strain (14 strains), feeding period during the growing period (short period n 10 to 20 weeks and long period = 10 to 24 weeks), protein level (low level = 10.2 percent and high level = 17.6 percent) and their interactions. Strain differences were significant with respect to most traits studied. The other two main effects, feeding period and protein level, were found also to differ, frequently and significantly. Most of the interactions were observed to be nonsignificant except for some first-order interaction such as strain X protein interactions for percent hen-day egg production after 50 percent of production (P < 0.05) and body weight at housing (P < 0.01), and feeding period X protein for sexual maturity (P < 0.05) and cost per hen (P < 0.01), while the second-order interactions were not significant for any trait. In spite of lack of significance in interactions between variables, there were some interactions which cannot be ignored. They would undoubtedly be significant with larger sample size and experimental procedures which would permit detection of small differences. Tests of significance of coefficients of correlation showed that strains differed in sign of correlations rather than in magni-tude. Treatments showed significant positive relationships of average egg weight with eggs per hen housed and of profit per hen with both eggs per hen housed and average egg weight, while other relationships with different sign were not significant.