1, the qualified rate of chicken is too low. The qualified rate is the ratio of the number of qualified chickens (the weight is within the standard weight 10%, and the shank length 104 ~ 106 mm) to the number of chickens in the house. The low pass rate indicates that there are more deaths during the brooding period, and the chicken's physique and uniformity are poor.

2. Unreasonable feed nutrition, unreasonable lighting program, food restriction and diseases.

3. Light is one of the important environmental conditions for chicken production, and the time and intensity of light play a vital role in chicken activity, material metabolism, growth and productivity. Incorrect food restriction will affect the development and maturity of reproductive system. During the 6 ~ 8 weeks in the late brooding period, sudden feeding restriction will affect the normal development of chickens. Diseases will also cause poor constitution of chickens, which will affect the normal development and maturity of chickens.