Use for marker technique - chromic oxide and chromogens - for determining the fecal output and measurement of feed intake by Brahman cattle (Bos indicus)

Abstract

An experiment was conducted in order to study the applicability of marker techniques - chromic oxide and chromogens - for the purpose of determining the fecal output and measurement of feed intake by Brahman cattle (Bos indicus). The chromic oxide was administered once daily in gelatine capsules. Fecal samples were taken at 6 A.M., noon and 6 P. M. and were totally collected during days, as well. Chromogens expressed in units per gram of roughages or feces (dry basis) and chromium oxide per cent of fecal dry matter, were determined on all the samples. The chromic oxide concentration of feces taken at 6 A.M., noon, 6 P.M. and bulked on seven consecutive days, as well as the mixed feces representing the total amount voided during 7 days period provided no accurate estimates of the total fecal output when the SMITH and REID (’55) equation was applied. The coefficients of correlation between the fecal output values determined conventionally and the estimates secured according SMITH and REID ('55) equation, were + 0.75 and + 0.89 for the total collection and the pooled 6 A.M. and 6 P.M. collection, respectively. Then, after using the SMTHI and REID ('55) equation, were proposed two other regression equations in order to correct the values and to obtain accurate estimates of the total fecal output in Brahman cattle. After correcting the total fecal excretion values it was possible to compute accurate levels of the dry matter intake employing the REID et al ( '50 - '52) equations. The modified procedure suggested by REID et al ('52) for calibrating the method of measuring the chromogens concentration, in the roughages, presented, for the Coleman Universal, model 14, the equation as follows: Y = 54.99-26.92 log X, where: Y = concentration of chromogens in the roughages, expressed in units per 100 ml of extract, X = per cent of transmitted light. In relation with the excretion pattern of feces, as small as + 3.2 g of chromic oxide administered daily, in capsule form showed reduced variation - 8% - among animals. The data suggested also that since the concentrate feeds contain very small quantities of chromogen absorving light at 405 mμ, large error was encountered when the chromogen content was determined on the whole ration. Then, more accurate results may be obtained if the chromogens are determined only on the roughage.