1. During a period of 2·5 years, every 3 months 221 different food items forming a ‘market basket’ were purchased, prepared and divided into twenty-three food-commodity groups. The ‘market basket’ was based on a study of the dietary intake of 18-year-old male, Dutch adolescents. In the (homogenized) food groups various minerals and trace elements were determined.

2. The mean daily amounts of cadmium (21 μg), mercury (0·7 μg), lead (32 μg), tin (0·65 mg), arsenic (38 μg) and bromine (8 mg) in the diet of adolescents, as calculated from the concentrations analysed in the food groups, were all (well) below the Food and Agriculture Organization/World Health Organization acceptable daily intake (ADI) value (Codex Alimentarius Commission, 1984).

3. The mean daily amounts of zinc (14 mg) and selenium (72 μg) seemed to be adequate compared with the Dutch recommendations, (Voedingsraad (Dutch Nutrition Council) 1986). The amounts of copper (mean value 1·5 mg/d) and iron (mean value 14 mg/d) in the total diet were marginal. Contents of calcium (1340 mg/d), magnesium (433 mg/d) and iodine (402 μg/d) were all well above the Dutch recommendations for male adolescents. Sodium intake, corresponding to 11 g sodium chloride/d, was higher than advised.

4. It is concluded that the amounts of As, Br and toxic heavy metals in Dutch total-diet samples of male adolescents are of little concern as regards health aspects. Among the essential trace elements, Fe and Cu contents seem to be marginal. Some concern regarding the salt content is indicated.

1. Because so little is known about the properties of lactitol as a possible alternative bulk sweetener to sucrose, it was tested in two large-scale experiments in laboratory rats. Matched groups of caries-active Osborne-Mendel rats were fed on uniform diets containing lactitol and compared with a sucrose control in both experiments, plus a xylitol control in the first experiment.

2. In the early stages of the experiments weight gains and food utilization were better on the sucrose than on the lactitol regimens. Body-fat storage was higher on the sucrose than on the polyol regimens.

3. At the end of 8 weeks the mandibular molars were examined for dental plaque accumulation and dental caries. The dental caries scores when 160 g sucrose/kg in the diet was replaced by lactitol were lower by a highly significant margin, bringing them down to the same low level as those on a 160 g xylitol/kg regimen.

4. Testing lactitol in a manufactured food product, shortbread biscuits, in comparison with ordinary sucrose biscuits, showed differences in plaque scores (significant) and caries levels (highly significant), with 60% fewer lesions on the lactitol regimen.

5. The results confirm the low cariogenic potential of lactitol, but show metabolic differences compared with sucrose.

1. Body fat, fat-free mass and total body water of ten lactating women were estimated from deuterium-dilution spaces and from skinfold thickness measurements. Deuterium-dilution spaces were calculated from the 6 h (equilibration) and zero-time (extrapolation) deuterium enrichments in saliva, urine, human milk and breath water vapour samples.

2. The deuterium spaces obtained by equilibration were statistically larger than those obtained by extrapolation. Isotope dilution spaces derived from deuterium enrichments in saliva, breath water vapour and human milk did not differ with the exception of the 6 h equilibration value of milk, which was greater than that estimated from saliva. Deuterium-dilution spaces estimated from urine were consistently smaller than those derived from the other biological fluids.

3. No significant differences in body fat, fat-free mass and total body water were observed between anthropometric measurements and deuterium-dilution methods, except for extrapolated values derived from deuterium enrichments in urine.

1. Supplementing the drinking water of laying hens with 600 or 2000 mg sodium chloride/l induced large increases in egg-shell defects without corresponding changes in egg production, egg weight or food and water intakes. A supplement of 2000 mg NaCl/l resulted in a high incidence of shell-less eggs.

2. The increased incidence of egg-shell damage in hens receiving the NaCl was associated with a decrease in egg-shell quality measured objectively. These responses persisted even after the NaCl was removed from the drinking water.

3. The NaCl treatment had little effect on blood acid-base balance and electrolytes, but significant reductions were observed in the carbon dioxide tension, and bicarbonate and calcium concentrations in the fluid surrounding the egg in the shell gland.

4. The poor shell quality appeared to be associated with a reduced supply of bicarbonate, rather than with an effect on Ca, in the lumen of the shell gland, although a reduced residence time of eggs in the shell gland may also have contributed to the problem.

1. Two experiments are described in which kinetic aspects of calcium metabolism were studied in housed lactating sheep consuming different fresh herbage species. The importance of protein supply was also investigated.

2. In Expt. 1, two groups (n 4) were offered, ad lib., a freshly cut ryegrass (Lolium perenne L.)-white clover (Trifolium repens L.) pasture containing 5·48 g Ca/kg dry matter (DM). One group was supplemented daily with 100 g protected casein. A third group (n 4) was offered, ad lib., freshly cut oats-Tama ryegass (Lolium multiflorum L.) herbage which had a lower Ca content of 3·07 g Ca/kg DM. Stable Ca and nitrogen balances were carried out during the first 7 weeks of lactation. At this stage 180 μCi45Ca were administered for Ca kinetic studies.

3. In Expt 2, eight sheep were offered, ad lib., a fresh ryegrass–white clover pasture, and paired on the basis of their udder size. One member of each pair was supplemented daily with 100 g casein via the abomasum and the amount of milk removed was equalized between pairs. Ca and N balances (12 d) and Ca kinetic studies (280 μCi 45Ca) were carried out during weeks 2 and 5 of lactation.

4. Rate of absorption of Ca increased, while rate of Ca secretion in milk and resorption from bone decreased as lactation progressed. Ca balances changed from negative to positive as lactation progressed in sheep offered ryegrass–white clover, but, while improving, were always negative in sheep offered oats–Tama ryegrass. Protein supplementation increased (18%) milk production of the ewes in Expt 1 and their retention of N in Expt 2.

5. The proportion of utilized Ca derived from the diet, as opposed to the skeleton, tended to increase as a result of protein supplementation.

6. Availability of Ca from ryegrass–white clover ranged from 0.19 to 0.32, even though only 50% of the net Ca requirement was derived from the diet. Availability of Ca from the oats–Tama ryegrass diet was similar, though in this case less than 20% of the net Ca requirement was derived from the diet. It was concluded that availability of Ca from forage diets may be lower than previously anticipated.

7. Faecal endogenous loss ranged from 16 to 40 mg Ca/kg body-weight per d, and was similar on both diets.

8. These and other findings are used to discuss more fully the subject of Ca nutrition in sheep, in particular, the implications of the strong homeostatic control of Ca absorption and the influence of protein status on the relative contribution of the diet and the skeleton in meeting the net Ca requirement of the ewe during lactation.

1. Two groups of eight 6–7-month-old wether lambs were offered either a frozen ryegrass (Lolium perenne L.)-white clover (Trifolium repens L.) pasture or a ryegrass-white clover hay, containing 12.1 and 6.4 g calcium/ kg dry matter (DM) respectively. Within groups the amounts offered to individual sheep ranged from 0.5 to 2.0 times the estimated maintenance energy requirements.

2. A single intravenous injection of 150 μCi 45Ca as CaCl2. 2H2O, and stable balances were used to determine absorption, faecal endogenous loss and balance of Ca.

3. Faecal endogenous loss of Ca increased by 1.2 mg/kg body-weight (W) per d with each g/kg W per d increase in DM intake regardless of the diet. At any DM intake the mean faecal endogenous loss was 5.5 mg/kg W per d higher in the sheep offered the frozen herbage diet when compared with those on the hay diet. At any Ca intake the mean faecal endogenous loss was 6.9 mg/kg W higher in sheep offered the hay diet compared with those on the frozen herbage.

4. At feeding levels of about 1.5–2 times the estimated maintenance energy requirement the observed faecal endogenous loss of Ca ranged from 35 to 50 mg/kg W per d, which is two- to threefold greater than the present estimate of the Agricultural Research Council (1980) of 16 mg/kg W per d.

5. A simple model to explain the variation in faecal endogenous loss of Ca between the present study with young sheep and that with lactating ewes (Chrisp et al. 1989) also offered herbage diets is developed, which incorporates the concept of a true endogenous loss related to DM intake and a net endogenous loss reflecting the extent of re-absorption of Ca endogenous losses within the gastrointestinal tract.

1. Six growing pigs fitted with portal and arterial blood cannulas were given a barley-fishmeal diet, either alone or supplemented with guar gum at 60 g/kg basal diet. Blood samples were taken during 8 h following test meals given at 08.00 hours.

2. Ingestion of the guar-gum-supplemented diet appeared to increase systematically portal and arterial levels of plasma urea. At peak values, 4 and 5 h after the test meal, this effect was statistically significant (P <0.05).

3. Irrespective of which diet was given, portal and arterial blood samples, withdrawn at the same time, were found to have about the same concentration of urea. This was found throughout the 8 h studied and implies that no net exchange of urea between the circulation and the gastrointestinal tract, as a whole, took place.

4. In the time-period 30–60 min following the test meal, guar gum significantly reduced the postprandial hyperglycaemia and hyperinsulinaemia in portal blood.

1. The associative effects of two fibre sources on ileal and overall digestibility of amino acids, energy and cell-wall components were studied by comparing wheat bran and soya-bean hulls in semi-purified diets given to growing pigs.

2. Castrated male pigs were prepared with ileo-rectal anastomosis to measure ileal digestibility, and overall digestibility was measured in pigs without anastomosis.

3. The three diets contained 190 g total fibre/kg dry matter (DM), derived from each fibre source or from a mixture of both fibre sources, so that each source provided half the amount of total fibre, and 170 g crude protein (nitrogen x 6·25)/kg DM by additions of casein.

4. The effects of fibre sources on the ileal digestibility of amino acids were additive for most amino acids; the only significant interactions were found for threonine, methionine and aspartic acid. In contrast with ileal digestibility, systematic negative interactions between fibre sources on overall digestibility of amino acids were noted.

5. There was no interaction between fibre sources in their effects on the digestibility of energy or of cell-wall components, irrespective of the site of digestion. The digestibility values were higher with soya-bean hulls than with wheat bran, especially at the faecal level.

6. It is concluded that ileal digestibility of amino acids provides a better estimate of amino acid availability, as ileal measurements allow a better discrimination between diets than faecal measurements when distinct fibre sources are used alone or in combination at the same total fibre content. In contrast, for energy, the measurement of digestibility at both faecal and ileal levels permits the estimation of the partition of available nutrients between the small and large intestines.

1. Maternal and umbilical cord plasma samples were collected from forty-seven Asian women, twenty-eight lifelong vegetarians and seventeen non-vegetarians, during delivery of their babies. The concentrations and fatty acid profiles of the plasma free fatty acid and triacylglycerol fractions were determined.

2. There were no significant differences between the levels of free fatty acid and triacylglycerol in either maternal or cord plasma from vegetarian compared with non-vegetarian Asian women. The fatty acid profiles of the lipid fractions in the two groups were similar. Total plasma free fatty acid levels in the maternal circulation correlated with umbilical cord levels.

3. The levels of linoleic acid in the maternal plasma free fatty acid fraction of the Asian women were much higher than previous reports on mixed populations of European women. In the Asian women arachidonic acid concentrations in both maternal and umbilical circulations were over four times higher than those reported for women unselected for race and diet.

1. The combined effects of feeding hydrogenated fats and varying the levels of biotin and linoleate (18:2ω6) on polyunsaturated fatty acids were studied in the chicken.

2. Biotin deficiency signs were not exacerbated by feeding hydrogenated fats or by diets low in linoleate for 21 d.

3. Biotin deficiency resulted in proportionately higher levels of 18:2ω6 and γ-linolenate (18:3ω6) in liver triglycerides, and lower levels of dihomo-γ-linolenate (20:3ω6) in liver and heart phospholipids irrespective of the 18:2ω6 level in the diet.

4. Biotin deficiency did not alter arachidonate (20:4ω6) levels in tissue lipids at 21 d.

5. Feeding high levels of trans-18:1 isomers with adequate biotin led to reduced 20:3ω6 and 20:4ω6 levels in liver and heart phospholipids with compensatory increases in ω3 fatty acids.

6. The trans-isomers of 18:1 were incorporated into several tissues of the chick. Incorporation was dependent on the levels fed. Very small amounts were incorporated into brain compared with other tissues when dietary trans-isomer levels were high, but were similar when dietary trans-isomer levels were low. The trans-18:1 isomers appear to be preferentially incorporated into phospholipids as opposed to triglycerides in heart and liver.

1. In a 4x4 Latin square design experiment, four cattle were given grass silage in two meals per d to satisfy maintenance energy requirements. In addition, sucrose (170 g/kg silage dry matter (DM)) was infused intraruminally at a constant rate with no nitrogen supplementation; with the infusion intraruminally of either casein (23 g/kg silage DM) or urea (8 g/kg silage DM); or with soya-bean meal (64 g/kg silage DM) fed in two equal portions.

2. Samples of duodenal digesta representative of a 24 h period were obtained using chromium-EDTA and ytterbium acetate for flow estimation and 35S as a marker of microbial N entering the small intestine. Samples of rumen fluid were also taken for estimation of rumen pH and concentrations of ammonia-N and volatile fatty acids. Estimates of apparent organic matter (OM) and N digestibility and of the rates of silage DM and N disappearance from porous synthetic-fibre bags incubated in the rumen were also made.

3. The N supplements had no significant effects on rumen pH, concentrations of volatile fatty acids, their molar proportions or the disappearance of DM or N from porous synthetic-fibre bags. N supplementation increased rumen ammonia-N concentrations (urea, P < 0.05; casein, soya-bean meal, not significant).

4. N supplementation had no significant effects on the digestion of OM, acid-detergent fibre or soluble carbohydrate.

5. Infusion of casein increased the quantities of total non-ammonia-N (not significant) and microbial N (P < 0.05) entering the small intestine daily and the efficiency of rumen microbial N synthesis (not significant). Giving soya-bean meal twice daily resulted in marginal increases in the quantities of non-ammonia-N and microbial N entering the small intestine, while infusing urea intraruminally had no effect.