Effects of a semipurified diet on carcass, fecal and urine characteristics of rats

Male (SD) rats fed a semipurified rodent food bar (RFB) diet, developed for Space Science, showed a decreased intestinal tissue mass but equal growth and energy conversion rates when compared to a natural (C) diet; therefore, this study was conducted to evaluate other possible partitioning of body tissue or nutrjent utilization. Rats (224) were housed in a thermally controlled chamber in 28 separate (30.5 x 43.2 cm) individually ventilated cages (22°C and 0.13 m/s). Mean rat weight started at 78 g and 90-day weight was 446 g. After 30, 60 and 90 days eight cages were shifted from C to RFB diet and housing density was reduced by two rats per cage. After 90 days, rats from each dietary treatment were placed in individual metabolism cages to determine feed and water consumption and fecal and urine production. Rats were then euthanized in precharged CO; containers; viscera were removed and carcasses were frozen and saved for analysis. A 95% level of significance indicated by ANOVA was used for inference. Feed intake was less for the C than the RFB (24 vs 29 g/d/rat) and water intake was greater for the C than the RFB (30 vs 20 ml/d/rat). For the C rats carcass protein (19.5%) and water (65%) was greater and fat (11 %) was less when compared to the RFB rats. The C rats had a mean fecal weight of 8.2 g/d/rat with a moisture content of 36% and a 27% nitrogen level on a dry weight basis; these values were greater than the RFB treatments. Urine volume, weight, osmolality, and pH were the same for both diets. Urine nitrogen was 3.3 and 5.0% for the C vs RFB respectively. In summary, the RFB resulted in shifts in body composition, had a dramatic effect on fecal volume and consequently influenced avenues of attaining water and nitrogen balance.