Influence of level of dietary fat on the growth of dwarf chickens.

Two strains of chickens, dwarf (dw) and nondwarf (Dw+), and three levels of supplemental dietary fat (none, moderate, and high) were included in a 2 X 3 factorial design to study the effect of dietary fat on growth. The lowered tibial ash, calcium, and phosphorus contents at 4 weeks of age and zinc content at both 4 and 8 weeks of age observed in the dwarf birds may reflect a predisposition to bone abnormalities. Improvements in weight gain (0 to 4 weeks) in response to supplemental dietary fat were observed in all birds but were less pronounced in the dwarfs. AT 4 weeks of age, the dwarf birds consuming the fat-supplemented diets had mineral contents of their tibia consistently lower than those of their dwarf counterparts fed the basal diet. At 87 weeks of age, there were no differences between strains in bone mineralization, but the 0 to 8 week weight gains were better for both strains fed the diet supplenented with a moderate level of fat. It appears that optimal bone mineralization of dwarfs to 4 weeks of age occurs at a lower level of dietary fat than that for nondwarfs. Beyond 4 weeks of age, a moderate level of suplemental dietary fat yielded optimal weight gains in both strains of birds.