Elisabet Forsum

Automatic total nitrogen analysis in nutritional evaluations using a block digestor

Abstract Experience obtained from more than 4 yr of using a block digestor in automatized total nitrogen analysis of various types of specimens (biological specimens, e.g., blood, urine, faeces, foods and feeds, protein concentrates) which are relevant in nutrition research is described. Results obtained on analysis of reference samples of casein during 1971–1974 revealed good reproducibility, although the samples were analysed over the 4 hr period and by different persons. The accuracy of the method in comparison with other methods was found to be remarkably good. The method allows rapid (in comparison with the Kjeldahl method) automatic analysis by the same setup for various specimens of interest in nutritional research with good accuracy.

Body composition and fat distribution during the first 2 weeks of gestation in ad lib .-fed and energy-restricted rats

Knowledge about changes in body composition during gestation is of interest when estimating energy requirements during pregnancy, and relevant since reproduction is often surprisingly well maintained in malnourished females. Due to difficulties in conducting such studies in humans, studies in rats are of interest. Therefore, maternal retention of fat and fat-free weight was estimated in rats during the first 2 weeks of gestation and during a corresponding time period in virgin controls. Groups fed ad lib. or 70% of ad lib. intake during the 4 weeks preceding conception and during gestation were studied. Retention was estimated by comparing pregnant and virgin rats with rats killed at the time of conception. Body fat was analysed chemically and fat-free weight was body weight minus body fat. Each rat was divided into twelve to fourteen parts and the fat content of each part was analysed. Pregnant ad lib.-fed rats retained more fat and fat-free weight than did virgin ad lib.-fed controls. In the energy-restricted group the pregnant rats retained more fat-free weight while virgin rats retained slightly more fat than did pregnant rats. The difference between pregnant and virgin rats with respect to the amount of fat in the different body parts was small in both feeding groups. Thus, the statement that fat stored at specific sites in the maternal body represents an important source of energy for use during lactation was not supported. The findings suggest that pregnancy stimulates growth of the maternal body and that chronic moderate energy restriction curtails this growth.