Composition of eggs from dwarf and normal chickens before incubation and at hatching in lines selected for 56-day body weight.

Comparisons of egg composition prior to incubation and when the chick had pipped through the shell were made for dwarf (D) and normal (N) chickens from lines selected for high (H) or low (L) body weight. Weight of moisture, ash, and fat decreased and nonlipid organic matter increased during incubation. The pattern for these components was the same on a percentage of egg weight basis except that there was no change in ash. Genotype by line interactions were significant for egg weight, moisture, ash, fat, and nonlipid organic matter before incubation and for all of these characteristics except fat at pipping. The interactions were due to values being lower for D than N in Line L, and D and N were similar in Line H. When egg component weights were expressed relative to egg weight, interactions were not significant prior to incubation but were present for moisture and fat at hatch. These data show that characteristics influenced by the sex-linked dwarfing gene are modified by the background genome.