1. Three experiments were conducted to determine growth of broiler chicks fed on test diets formulated to be deficient or adequate in tryptophan (Trp) using gelatin by-product as a means of generating a Trp deficiency. Growth response estimates of broiler chicks to graduations of Trp were determined by dose-response criteria and regression analyses. Experiments were conducted using broiler chicks from 1 to 20 d of age. 2. Broiler chicks fed Trp-deficient diets had poor body weight gain, feed intake and feed conversion. Recommended total Trp needs were 2.0, 2.1 and 2.2 g/kg for feed intake, body weight gain and feed conversion, respectively. 3. Blood plasma Trp exhibited a sigmoidal trend while blood plasma glucose increased in a linear manner to supplemental Trp. Physiological stress variables measured were unaffected by dietary Trp.

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1. Morphological development of the heart in fast-growing, meat-type fowl of both sexes was studied. 2. In 4 experiments, fowl were weighed, killed and hearts were dissected at 0, 20, 34, and 48th d of age. Heart weight (HW), length (HL), diameter (HD), and thickness of the right ventricular wall (RVW) and left ventricular wall (LVW) were determined. 3. This is the first description of sexual dimorphic differences in the heart of fowl. 4. Results indicate that males have greater HW, HL, and LVW thickness than females. However, thickness of the RVW during the embryonic period, as indicated by thickness of the RVW at hatching in females, exceeds that of males.