The Effect of Levels of Protein and Vitamin B12 in Hen Diets on Egg Production and Hatchability of Eggs and on Livability and Growth of Chicks

The effects of feeding different levels of protein and vitamin B12 on egg production and hatchability of eggs of Single Comb White Leghorn hens were studied. Diets containing 16 and 32% corn-soybean meal protein with and without 10 μg. of vitamin B12 per kg. of diet were employed. Egg production and fertility of eggs were not significantly affected by protein level or vitamin B12 supplement. However, increasing protein level in the hen diets resulted in a significant decrease in hatchability. Vitamin B12 supplementation of both diets significantly improved hatchability of eggs. However, the supplementary vitamin B12 was not adequate to support desirable hatchability when the diet contained 32% protein. The high level of protein, and the addition of vitamin B12 to the 16% protein diet significantly increased egg weight. Chicks hatched from eggs produced by hens fed the different experimental diets were used to study the effect of breeder diets on chick growth and livability. A deficiency of vitamin B12 in the breeder had a detrimental effect on chick growth and livability. Increasing the protein level of the chick diet from 22 to 32% resulted in a further decrease in growth when the chicks were derived from vitamin B12 deficient hens. A high level of protein in the breeder diet also depressed chick growth. This growth depression was not counteracted by a dietary supplement of 500 μg. of vitamin B12/kg., by an oral dose of 50 μg. of vitamin B12/chick at hatching, or by an injection of 1 or 10 μg. of vitamin B12/bird at hatching. Vitamin B12 supplied through the hen diet was more effective than supplementation of chick diet in stimulating early chick growth. Mortality was higher in chicks hatched from hens fed the 16% protein diet than in those from hens fed 32% protein. This was the reverse of embryo mortality during incubation.