MINIMAL TIME REQUIRED FOR DETECTING DIFFE RENCES BETWEEN SOY AND GELATIN USING URIC-ACID EXCRETION AND PURINE ENZYMES AS INDICATORS OF PROTEIN-QUALITY IN CHICKENS

Previous studies shown that in chickens the hepatic activities of the purine enzymes Xanthine Dehydrogense and Nucleoside Phosphorylase and the uric acid excretion can predict the quality of die protein consume d in a very short time. In these studies even though the experimental time was short, the time used for the conditioning of the chickens was long and included five days with six chickens per cage and then five to six days for progressively changing the chickens to individual cage s in order to avoid the stress associated with the isolation of the an imals. Thus the purpose of this study was to determine the minimal tim e required to detect differences in these parameters after feeding a s oy-met and a gelatin diet and eliminating completely the time required for the isolation of the chickens. Thus, 76 one day old Warren male c hickens were placed in groups of six on a soy-met powdered diet during five days and on day six all the chicken were placed in individual ca ges and one halve was offered the same diet while the rest received a gelatin diet. Then on day 1, 2, 3, 5, 7, 1 0 and 15 after the diet cha nge five chickens on each diet were sacrificed and the activity of the liver purine enzymes as well as the uric acid excreted were determine d. The results showed that the abrupt isolation of the animals was ass ociated with a transient reduction in growth and in an increment in th e activity of both enzymes and in the excretion of uric acid which was more evident when these parameters were expressed as a function of th e nitrogen consumed. These effects of the isolation dissipated in appr oximately three days but regardless of this effect, the activies of th e enzymes and the excretion of uric acid corrected by the nitrogen con sumed were substantially higher in the gelatin fed animals than in the soy-met fed animals from the first day after diet change and continue d elevated throughout the experiment, indicating that the quality of t he protein consumed affected both the purine enzymes and the uric acid excrtion in a very short time. In general these results show that the abrupt isolation of die chickens caused a transient induction in the production of uric acid and also in the purine enzymes involved in its synthesis. This induction however did not interfere with die use of t hese parameters in the prediction of protein quality since it happened both in the chickens fed soy-met and also in those fed gelatin. These results confirmed that these methods are appropriated for determining protein quality in a very short time and also that the conditioning p eriod can be substantialy reduced.