Studies on the Effect of Quantity and Type of Fat on Chick Growth

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Abstract
In experiments conducted with chicks highly significant growth increases were obtained by increasing the vegetable oil content of purified diets from 3–5 to 10% and practical diets from 3.4 to 10.1%. The responses were obtained with purified diets supplemented with sources of unidentified growth factors and with basal purified diets. The growth of chicks fed hydrogenated vegetable oil was significantly less than that of chicks fed an equal quantity of corn oil or soybean oil, indicating that the growth-promoting effect of the oil was markedly reduced during hydrogenation. Lard also appeared to have less of this effect when added to purified diets supplemented with unidentified factors. The fraction of corn oil composed chiefly of glycerides not readily subject to molecular distillation was found to promote growth to approximately the same extent as the intact oil. The evidence indicated that the improved growth was not due to a lack of capacity of the chicks to eat more feed, or to a more optimal concentration of energy unrelated to food capacity. The evidence also indicated that the response was not due to the lower specific dynamic action of fat making more energy available for growth. The effect, therefore, appeared to be caused either by an unknown substance not removed by molecular distillation or by heretofore unrecognized growth-promoting characteristics of some of the known components of fat.