It was reported previously by the authors that the hatching time and the sex-ratio in chicks might be affected by the breed, the age of the breeding stocks and the breeding season.
The present experiments were carried out to clarify the relation between the hatching time and the sex-ratio due to the egg weight in the two different poultry farms.
Three sorts of chicks were used, namely, the hybrid between Rhode Island Red (R. I. R.) males and Rhode Island White (R. I. W.) females, that between White Leghorn males and Barred Plymouth Rock (B. P. R.) females and that of the Shaver Strain of White Leghorn (W. L.).
The hatching time was recorded at 3 hours intervals from the start of hatching to 36 hours thereafter, and the egg weight was classified at 2g intervals from 53g to above 65g.
1. In the hybrid between R. I. R. males and R. I. W. females, and that between W. L. males and B. P. R. females, female chicks tended to hatch in the early period of hatching and male chicks tended to hatch in the late period.
On the ralation between the hatching time and the sex-ratio of their chicks, the differences were recognized to be significant at 0.1% level in the former hybrids, and 1% level in the latter ones.
2. With regard to the incubation period between males and females, less difference might be recognized in the standard egg weight than in large and small eggs in hybrids between R. I. R. males and R. I. W. females, and between W. L. males and B. P. R. females, in which a significant difference was exsisted between the hatching time and the sex-ratio.
3. In the Shaver Strain of W. L., the considerable differences between the hatching time and the sex-ratio were found among the stocks of different age, though the difference was not significant statistically.
The hatching time of the chicks from elder breeding stocks might be decreased, and it was considered to be affected by the laying season.
4. From above mentioned results, it might be concluded that the hatching time and the sex-ratio in chicks are affected considerably by the breeds of their parents.