GENOTYPE BY ENVIRONMENT INTERACTIONS IN LAYING HENS BASED ON RELATIONSHIP BETWEEN BREEDING VALUES OF SIRES IN TEMPERATE AND TROPICAL ENVIRONMENTS

This study was conducted to evaluate the significance of genotype by e nvironment (G x E) interactions for tropical poultry breeding. Three e nvironmental conditions were considered: controlled normal-temperature (20+/-2 C, CN) and controlled high-temperature (32 C, CH) housing in Germany as well as natural open tropical housing in Malaysia (22 to 34 C, TO). Eighty-four sires were considered as genotypes. Their 5,352 p rogeny were tested simultaneously over three environments. For each si re, its part breeding value (BV) was estimated within each environment for each performance trait. Correlations between these BV for a pair of environments were used to estimate the magnitude of G x E interacti ons and the degree of relationship between them to demonstrate their i mplications on breeding strategies. Differences between observed and e xpected genetic correlations of BV for body weight, egg weight, egg nu mber, egg mass, feed intake, and production efficiency as a fraction o f the expected correlation were 5.1, 4.0, 36.7, 36.5, 17.7, and 31.6%, respectively, suggesting greater significance of G x E interactions f or reproduction and production efficiency. The relationships between B V over the three environments were linear for most of the traits studi ed, but the coefficients of determination were dependent upon the magn itude of interactions involved. Relative efficiencies of indirect sele ction in CN or CH for performance in TO were also very low.