Comparisons of Control and Selected Strains, Strain Crosses, and Commercial Stocks of Leghorns for Egg Production Efficiency

Abstract

Abstract Agriculture Canada Animal Research Centre Leghorn Strains 1 and 8, selected for a number of economically important traits but primarily for early egg production rate and egg numbers respectively, were compared with their respective unselected controls, Strains 5 and 7, two reciprocal crosses of the selected strains, designated 18 and 81 (sire strain shown first), and a commercial stock. Two diets (high and low protein with similar protein:energy ratios) were fed during the testing of these stocks. Birds on the higher plane of nutrition consumed less feed and produced eggs with a slightly higher proportion of yolk; however, these birds were less efficient on the basis of solids and gross energy output: intake and egg yield: feed intake. Selected strains produced more large eggs that had a higher percentage of egg white solids and a lower proportion of yolk than their respective control strains. Strain 1 showed generally greater differences in comparison with its control than Strain 8. In general, feed efficiencies were higher in the selected strains than in their respective controls. The strain crosses exceeded the parental strains in egg production, egg weight, and several measures of feed efficiency. Reciprocal effects were observed in egg weight, egg yield, and efficiency. Egg production of the commercial stock ranked between the two crosses. This study provided evidence that multitrait selection for high egg production and related commercially important traits increases the efficiency of egg production and influences egg composition. Improvements from strain crossing were due mainly to increases in egg production and egg size.