Experimental details

1. Subjects
Six boys and four girls, 52 to 70 months old, were selected among pre-schoolers from agricultural villages in the northwestern part of South Korea, about 48 km from Seoul. Their characteristics are given in table 1. They were healthy and normal, except for the intestinal parasites, based on medical history, physical examination, and laboratory analyses of blood and urine specimens, including transaminase and alkaline phosphatase activities.

2. Study Environrnent
The tests were done in a field metabolic unit during the fall. Outdoor temperature ranged from 3 to 25 C, and indoor temperature from 18 to 24 C.

3. Physical Activity
The activities of these children were normal for their age.

4. Duration of the Study
The study iasted ten weeks, divided into three periods: a. The first feeding period (BfV) was before treatment with a vermicide and lasted four weeks. b. The second period lasted two weeks, with a free-choice diet comparable to what the subjects ate at home. Ten mg/kg of Combantrin was given on the first day of this period. c. The third period (AV), after the vermicide treatment, lasted four weeks.

TABLE 1. Characteristics of Subjects

* Surface area (SA) and BMR were measured on the last day of the eighth experimental week. SA w0.425 x H0.725 x 71.84.
** BfV - before vermicide; AV ** after vermicide.
*** Approximate energy requirements: estimeted - BMR (kcal/day) x 1.7/body weight (BW); FAD/WHO = 1973 recommendations.

5. Dietary Intakes
Because of a generally low intake of animal protein, a daily supplemental feeding consisting of 150 ml of whole cow's milk was added to each subject's ordinary daily diet for one month before initiation of the study. The experimental diets were devised to provide approximately 100 kcal/kg/day and four levels of dietary protein (1.50, 1.75, 2.00, and 2.25 g/kg/day: diets A, B, C, and D, respectively), based on the local diet (see table 2). The four levels of dietary protein were fed in four consecutive weeks, both before and after treatment with the vermicide (BfV and AV, respectively). Three isoenergetic and isonitrogenous meals and light snacks were provided each day. Additional food intake, mainly rice, was allowed on request, especially in the AV period. A record was kept of each subject's food intake. Vitamin and mineral supplements were given once a day to meet requirements. Table 3 gives the estimated essential amino acid content and the chemical score of the experimental diets.

6. Indicators and Measurements

1. Complete urine and faecal collections were made daily throughout the two experimental feeding periods. Total nitrogen (micro-Kjeldahl), urea nitrogen (Folin-Wu), and creatinine (diacetyl-monoxime) were measured in the urine collected during the last four days of each week with a given diet. Nitrogen was also measured in faeces pooled during the same four days and in aliquots of the diets.
2. Fats (Soxhlet) and ash (combustion) in food and faeces were measured. Carbohydrates were calculated by subtracting protein, fat, ash, and moisture from total weights of food and faeces. Their energy contents were calculated using 4, 4, and 9 kcal per gram of carbohydrate, protein, and fat, respectively.
3. Nude body weight was recorded daily after the subject had voided the first morning urine before breakfast.
4. Venous blood samples were drawn before breakfast on the first and last days of the study. Haemoglobin, haematocrit, serum glucose, urea nitrogen, creatinine, SOOT, alkaline phosphatase, total proteins, albumin, and globulins were measured.
5. Stool examinations for the quantitative determination of helminth eggs were performed each of the first three days in both experimental periods (BfV and AV). The parasites expelled on the first three days after treatment were identified and counted.
6. The basal metabolic rate (BMR) was measured on day 14 of the AV period by the Douglas bag spirometer method.
7. The faecal obligatory nitrogen losses were estimated from the Y intercept of the regression equation of faecal nitrogen (Y) on nitrogen intake (X) (table 4). Digestibilities of protein and energy were expressed as the percentage of intake that was absorbed.

TABLE 2. Food Ingredients in the Daily Diet of a 17-kg Child (g/day)

TABLE 3. Essential Amino Acid Composition of Experimental Diets (mg/g Protein)

* First limiting amino acid.

An obligatory faecal nitrogen loss of 32 mg/kg/day was used to calculate "true" protein digestibility. True nitrogen balance was calculated assuming 5 mg N/kg/day for integumental and miscellaneous losses. The biological value (BV) of protein was estimated as:

BV = (intake-faecal-urinary + faecal and urinary obligatory losses) X 100/(intake-faecal + faecal obligatory loss)

where the obligatory faecal and urinary losses were assumed to be 32 and 48 mg N/kg/day, respectively. The net protein utilization (NPU) was calculated from the biological value and digestibility.