Effect of Hatching Egg Size from Semi-Dwarf and Normal Maternal Meat Parent Genotypes on the Performance of Broiler Chickens

Hatching eggs were collected from two meat parent genotypes (normal and semidwarf) between 200 and 210 days of age and sorted by weight into four quartiles. Eggs from the light and heavy quartiles were retained for a comparative testing of hatching quality and progeny performance. Egg weight differed significantly between the two genotypes. Genotypes and egg size had no significant effect on hatchability. Significant genotypic and egg size effects were observed on fertility and day-old chick weights but not for mortality during rearing. Maternal genotype had no significant effect on the body weights of broiler progeny at either 28 or 49 day s except that at 28 days males from semi-dwarf maternal parents were lighter than males from normal maternal parents. Egg size had a significant effect on both male and female body weights at all ages with broilers hatched from the small eggs being lighter than those hatched from large eggs. Feed conversion was unaffected by genotype, but chickens hatched from large eggs exhibited better feed conversion compared with those hatched from small eggs. The percentage of Grade A carcasses was not affected by genotype but was significantly higher among male broilers hatched from the small sized eggs. Egg size had a significant effect on monetary returns as broiler chickens hatched from the smaller eggs returned approximately 7¢ less per bird compared with broilers hatched from the larger eggs. There was no significant difference between monetary returns from broiler chickens from either normal or semi-dwarf maternal parentage. This strongly supports the future adoption of the semi-dwarf maternal parent by the industry.