Embryonic and Early Post-Hatching Growth Patterns of Dwarf Broiler-Type Chickens

Dwarf (dw) chicks were significantly heavier at hatching and had significantly more unabsorbed yolk material than nondwarf chicks of the same sex from the same sized eggs. Body weight minus yolk did not differ between the two groups within sex. In a separate trial where no adjustments for egg weight differences or sex were made, hatching weight of dwarf and normal chicks did not differ, but body weight minus yolk was significantly reduced in dwarfs. As a result of these differences, residual yolk sac weight was again significantly larger in dwarfs. No significant difference in leg length between dwarf and normal chicks at hatching was observed. The regressions of body weight at 2, 4, 6, 8, 10 and 12 weeks of age on weight of the egg from which the chick hatched were highly significant for females in a dwarf broiler-type population. In contrast, the regressions were significant only through six weeks of age in males. Phenotypic correlations between body weight and egg weight exhibited a similar pattern. No significant quadratic regressions were observed between these two variables.