Effects of Protein and Fat in the Diets on Hatchability of Eggs and Chick Growth

An experiment was conducted using Single Comb White Leghorn (S.C.W.L.) hens to study the effect of fat and vitamin B12 (50 μg./kg.) additions to a 32% protein diet; on production parameters, hatchability and chick growth. Levels of protein, fat and vitamin B12 had no significant effect on egg production, however, vitamin B12 supplementation of the 32% protein diet gave a considerable improvement in egg weight. Feed consumption was highest on the 32% protein diet. Adding 8.5% fat to the 16 and 32% protein diets significantly reduced feed intake. The 32% protein diet supported the poorest hatchability. Animal fat (8.5%) or vitamin B12 (50μg./kg.) added to the 32% protein diet supported satisfactory hatchability. On the contrary, addition of 8.5% fat to the 16% protein diet significantly reduced hatchability of eggs. A high level of protein in either the breeder diet or chick diet depressed chick growth, and the combination of both caused a further growth depression. Added fat in the breeder diets had a slight growth depressing effect on chicks. When the chicks were fed a 30% protein diet with 8% added fat, the chicks hatched from hens fed the breeder diets with added fat grew significantly poorer than those hatched from hens fed a similar diet without added fat. Chicks that were hatched with a vitamin B12 carryover were not affected by dietary fat additions. Mortality of chicks hatched from hens fed the diets with added fat was high and adding fat to the chick diet reduced mortality. Vitamin B12 content of egg yolks was increased by adding fat to the 32% protein hen diet. Hatchability of eggs from these hens was higher than for eggs from hens fed a similar diet without added fat. The vitamin B12content of livers of day-old chicks was correlated with increased growth of chicks fed vitamin B12 deficient diets.