Application of the Chromic Oxide Indicator Method to Balance Studies with Growing Chickens

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Abstract
The colorimetric method of Schürch and co-workers for the determination of chromium has been modified by measurement of color density at 375 mµ. With this modification, the method is highly sensitive and conforms to the Lambert-Beer law. The index method of conducting measurements of nutrient balance using chromic oxide has been applied to groups of growing chickens under ad libitum feeding conditions. Collecting excrement in unit periods of 24 hours is satisfactory for circumventing the effect of the diurnal rhythm of excretion of cecal droppings. Changes in level of feed intake are reflected quickly in the level of chromic oxide in the excrement, with the result that any single 24-hour collection may be subject to serious error. A useful criterion for determining the validity of a balance obtained by this method is the agreement between two or more successive 24-hour periods in the chromic oxide content of the excrement. Compared to results obtained by measurement of total intake and excretion, the index method gave more consistent and probably more accurate results of balance measurements under the conditions employed.