Total parenteral nutrition with different ratios of fat/carbohydrate at two energy levels: an animal study.

Different regimens of total parenteral nutrition were evaluated in 64 growing rats, during a 10-day period. Thirty-two rats were kept at a low energy regimen (270 kcal/kg body weight per day), and the remaining rats were infused with a high energy solution (350 kcal/kg/day). At each energy level, four fat/carbohydrate (CHO) nonprotein energy ratios were tested: 0% fat/100% CHO (no fat); 6% fat/94% CHO (low fat); 30% fat/70% CHO (medium fat); 60% fat/40% CHO (high fat). A daily supply of 0.9 g nitrogen/kg of a well balanced amino acid solution was administered to all rats. Growth, nitrogen balance, net nitrogen utilization, and blood status were evaluated. Carcass, liver, and muscle composition were investigated with respect to protein, fat, and water content. Liver and body composition was similar between groups at the same energy level. At the higher energy level the fat deposition was increased. At the low energy level, rats from no fat and low fat groups lost weight during the first 3 days of the experimental period. The medium fat groups showed the highest weight gain at each energy level. This suggests the importance of the presence of fat in total parenteral nutrition programs. During the last days of the experimental period, all rats gained weight, and showed a positive nitrogen balance. All groups given 350 kcal/kg/day gained weight more rapidly and showed a better nitrogen balance and utilization than the corresponding group given 270 kcal/kg/day. This study emphasizes that a well-balanced proportion of energy and substrates is important.