HETEROSIS AND RECIPROCAL EFFECTS FOR EGG-LAYING TRAITS ESTIMATED FROMA FULL DIALLEL CROSS WITH 6 COMMERCIAL WHITE LEGHORN LINES, USING MIXED-MODEL ANALYSIS

A diallel cross between six commercial White Leghorn lines was perform ed and measurements were done on a total of 1162 cages (2 for 3 full-s ibs housed per cage) to an age of 60 weeks. Egg production traits then -day and hen-housed egg numbers, hen-housed egg yield (mass), hen-day rate of egg production), egg weight and egg quality traits (specific g ravity deformation, and breaking strength) were analysed using a mixed (sire) model. Egg production traits showed the highest heterosis, ran ging from 0.6 to 13.6% (of parental average) between crosses. Egg weig ht showed moderate heterosis: -0.5-5.3%. Specific gravity showed negli gible effects of heterosis (-0.1 to 0.3%) while other egg quality trai ts showed substantial but non-significant heterosis: deformation -10.9 to 3.9% and breaking strength -2.3 to 7.3%.