Influence of dietary levels of sodium chloride and protein on growth, nitrogen balance and body composition of the growing rat
American Journal of Physiology 182(1): 83-88
Young, growing rats were fed various protein and NaCl dietary levels according to a factorial design consisting of 3 casein levels (10, 25, and 40%), with 3 treatments for each casein level The 1st treatment involved the ad libitum feeding of a ration containing 15% NaCl; the 2d treatment, the same amount of basal ration consumed by the 1st but minus the NaCl; the 3[image]. treatment, the basal ration ad libitum. In the ad libitum- ed comparisons a growth depression caused by high NaCl fe dings was of the same magnitude at all casein levels. Gains in fat, water, N, ash, Na and K were less with the high NaCl intakes than with the ad libitum-fed controls. In the pair-fed comparisons, the gains of the rats on the high NaCl intakes were higher than those of the pair-fed mates. This additional weight gain was due to the increased weight of the gastrointestinal tract plus its contents. The weight of the rats when eviscerated was equal to the pair-fed comparisons. In these comparisons the gains in water, Na and K were the same. The gain in N and ash were less for the rats on the high NaCl intakes. There was a differential response in the gain in fat since the high NaCl intakes depressed fat gain more markedly at the 25 and 40% dietary casein level than at the 10% casein level. In the balance study, the addition of NaCl at 15% of the ration increased apparent N digestibility. However, a smaller percentage of the N was retained by the high NaCl rats than by either the pair-fed or the ad libitum-fed controls.