An investigation was carried out into the effects of some dietary factors on the serum cholesterol and serum total lipid levels in both normal and hyperthyroid chicks. Dietary factors investigated were the effects of two levels of protein, two levels of fat, and two levels of vitamins. Basal diets were fed at either a 20% or 26% protein level and when dietary fat was investigated the dextrose of the basal diet was substituted for a hydrogenated vegetable oil to make up 12% of the diet. The

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... in supplement in the high vitamin diets fed consisted of additional amounts of the following B complex vitamins: choline chloride, calcium panthothenate, folacin, niacin and riboflavin. Chicks were rendered hyperthyroid by feeding diets containing 0.02% iodinated casein. Hypothyroidism was induced by the feeding of 0.1% thiouracil. Normal chicks showed lower levels of serum cholesterol and serum total lipids when they were fed basal diets consisting of 26% protein level than when fed basal diets consisting of a 20% protein level. Normal chicks fed high fat diets showed higher levels of serum cholesterol and serum total lipids than normal chicks fed low fat diets. Normal chicks fed diets low in the B complex vitamins showed higher levels of serum cholesterol than normal chicks fed diets high in the B complex vitamins. The growth rate of chicks rendered hyperthyroid varied. In many instances hyperthyroid chicks grew at a significantly faster rate than normal chicks while in some instances no differences were noted. In some cases chicks rendered hyperthyroid showed depressed growth rates. No clear explanation could be given for such an effect on the growth rate of hyperthryoid chicks. It seems reasonable, however, to suspect that seasonal changes may affect thyroid activity and consequently the growth rate of the chicks in question. No differences were noted between the serum cholesterol and serum lipid levels from hyperthryoid chicks fed the basal diets containing 20%, and 26% protein. Hyperthyroid chicks, however, sho [...]