Effect of Dried Egg Yolk, Oils and Fat on Chick Growth

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Abstract
A highly significant increase in chick growth rate was obtained by the isocaloric-isonitrogenous substitution of dried yolk, yolk oil, corn oil, or soybean oil in either a 32 or a 22% protein, high-energy diet. The substitution of fat calories for carbohydrate calories on an isocaloric basis in isonitrogenous diets resulted in significantly improved weight gains. This was true for equalized nutrient intake as well as for ad libitum feeding. Highly significant differences in growth were noted even though the Calorie/protein ratios were constant. If the growth response to yolk is due to a growth promotant, then these results indicate that corn oil, soybean oil, lard, and coconut oil also contain a common growth stimulant, and that this can be extracted from dried yolk with fat solvents, hence giving the response with egg oil. These results also show that animal fat was just as effective as vegetable oil in growth stimulation. The relatively more saturated lard, coconut oil, and egg oil were just as effective as the less saturated corn and soybean oil. Although this difference in degree of saturation had no effect on growth, lack of growth stimulation from hydrogenated coconut oil suggests that unsaturated fatty acids are involved, or that the growth promotant present in coconut oil is inactivated by hydrogenation.