[Studies on reducing the crude protein content of feeds fed to chicks and young hens (laying stock)].

2 rearing trials were carried out on a total of 8550 hybrid chicks (White Leghorn) to investigate in which way food mixtures containing reduced levels of crude protein (supplemented or unsupplemented with amino acids) might influence the growth of chicks and young hens. Decreases from 21.5% to 16.5% in the crude protein content of chicken feed and from 15% to 13% in feeds feed to young hens (greater than 8 weeks of life) did not reduce the live weight of birds at the end of the rearing period to any appreciable extent. No clearly defined differences were found to exist between the different types of feed tested concerning the amount of food and energy consumed per unit of weight gain and the mortality rate among the birds; it was shown, however, that the demand for crude protein per unit of weight gain was clearly reduced in birds reared at the lower crude protein level. For young hens receiving the diet poorer in protein the date when the birds began laying was slightly delayed. Otherwise, no statistically significant differences were found to exist between the young birds fed varying levels of crude protein, concerning the age at 50% laying performance and other parameters that are characteristic of the entire laying period (laying performance, weight of individual eggs, food consumption, mortality, fertilization of hatching eggs, hatchability of eggs). It appears that the feeding of a reduced protein diet to chicks and young hens (laying stock) did not have any detrimental effect on the growth and later laying performance of the birds. Apart from the fact that the demand for protein feeds is considerably reduced during the rearing period the costs of feeding per bird can also be cut down.