Abstract
Six hundred and seventy White Plymouth Rock female chicks, hatched in the spring of 1969, were reared at Gifu prefectural poultry breeding station and Gunma prefectural livestock experiment station to study on the grower diets and requirement of the protein and energy in the laying period.
The experiment was carried out on two groups. One group was given normal grower diets and served as a control. The other group was first given low-lysine diet up to the age of 8 weeks and then high-energy, low-lysine diet up to the age of 24 weeks. After this age, both groups were given nine kinds of laying diets comprising the combinations of three levels each of crude proteins (12%, 16% and 20%) and total digestive nutrients (60%, 66% and 72%) up to the age of 64 weeks. The results obtained are as follows:
1) At the age of 24 weeks, the mean body weight of chicks fed with high-energy, low-lysine diet was restricted within 70% of that of control chicks and the feed intake per chick was smaller by 2.8kg. In the rate of raising, however, any significant difference could not be observed between the two groups.
2) During the period from 24 to 64 weeks of raising, many criteria, such as egg weight at sexual maturity, egg production, egg weight, rate of hatchable egg and feed cost per hatchable egg, were all in favor of the high-energy, low-lysine diet although the sexual maturity was retarded.
3) Diets containing 12% of crude protein retarded the sexual maturity but failed to exert any adverse effect upon egg production.
4) With the increase in the amount of total digestive nutrients contained in they diets, the feed intake diminished and the final body weight increased.
