An in vitro method was developed to predict inorganic P release from maize-soyabean poultry feeds containing supplemental phytase (EC31·3·8), and to quantify the effect of acid phosphatase (EC 3·1·3·2), fungal protease (EC 3·4·23·6) and Aspergillus niger cellulase (EC 3·2·1·4) on phytate dephosphorylation. Pepsin (EC3·4·23·1) and pancreatin digestion periods were preceded by a 30 min pre-incubation at pH 5·25 to simulate digestion in the crop of poultry. Pancreatin digestion was carried out in dialysis tubing, with a ratio of about 1:25 (v/v) between the digesta and dialysing medium, to simulate gradient absorption from the duodenum. The feed:water ratio was kept within physiological limits and a constant proportion of feed weight to digestive enzymes was maintained. There was a linear response to increasing dosages of phytase up to 1000 phytase units (FTU)/kg feed, and to increasing phosphate concentration in feeds. In vivo validation was performed with growing turkeys (1–3 weeks) fed on diets containing 12 g Ca/kg and 0, 500 or 1000 FTU phytase/kg in a factorial arrangement with 0, 1, 2 or 3 g supplemental phosphate/kg (from KH2PO4). After a simple transformation (variable/in vitro P = f (in vitro P)), amounts of P hydrolysed from feed samples by in vitro digestions correlated with 3-week body-weight gain (R 0·986, P < 0·0001), toe ash (R 0·952, P < 0·0001), feed intake (R 0·994, P < 0·0001) and feed efficiency (R 0·992, P < 0·0001). The dephosphorylating ability of phytase in vitro was significantly enhanced (P < 0·05) by the addition of acid phosphatase. Fungal acid protease and Aspergillus niger cellulase also enhanced the dephosphorylation process in vitro.

Postprandial kinetics of porto-arterial concentration differences of glucose (G), galactose (Gal), L-lactic acid (LA) and amino-N (AN) were studied in the piglet after the ingestion of 107 colony-forming units (cfu) Sporolactobacillus P44 (SP), or 106 cfu Bacillus cereus IP5832 (AC), or 106 cfu of a combination of Lactobacillus acidophilus, L. fermentum and L. brevis (AB)/g feed. Sixteen fistulated piglets (portal vein and brachiocephalic trunk; mean body weight 22 (SD 2) kg) were used. The diet was based on skimmed milk (320 g/kg), barley (300 g/kg), wheat bran (110 g/kg), maize (100 g/kg) and lactose (70 g/kg). The postprandial blood kinetics, four measurements per animal at 1-week intervals, were studied for 6 h after the ingestion of test meals of 400 g basal diet (BD) or this diet supplemented with the bacteria (SP, AC and AB respectively). Areas of porto-arterial concentration differences (APACD) of G, Gal and LA were not influenced by the bacteria supplements. APACD of AN was significantly higher after the ingestion of the SP diet than that estimated for BD.

A population sample of 375 men and women cigarette smokers were recruited to take part in a prospective study of smoking cessation to test the hypothesis that stopping smoking is associated with an increased consumption of the essential fatty acid linoleic acid, which explains the concomitant reduction in risk of coronary heart disease. Diet was assessed using a 10 d weighed record in 301 smokers at baseline, 153 at 4-month follow-up, of whom twenty-six had quit smoking, and 122 at 1-year follow-up, of whom twenty had quit. Compared with continuing smokers, those who had quit at the 4-month follow-up (mean 10 and 13 weeks for men and women respectively) had statistically significant increases in body weight (5%), energy intake (13%), total dietary fat (24 %), all specific types of dietary fat (26% polyunsaturated fat, 26% linoleic acid, 30% eicosapentaenoic acid, 23% monounsaturated fat and 22% saturated fat) and vitamin E intake (19%). The foods which appeared to contribute to increases in energy and fat intakes at the 4-month follow-up were vegetable oils and polyunsaturated margarines, processed meats and meat pies. By follow-up at 1 year (mean time since quitting 31 and 41 weeks for men and women respectively) there were no detectable differences in energy and total fat intakes. However, intakes of eicosapentaenoic acid and pteroylglutamate (folate) were statistically significantly higher in the quitters compared with the continuing smokers (37% for eicosapentaenoic acid and 16% for folate). We conclude that the short-term increase in dietary intake of linoleic acid, which is not sustained by 1 year, cannot explain the reduction in risk of coronary disease following smoking cessation.

The effect of the energy density (ED) of feeds offered as a choice on the diet selection of sheep, and the relationship between the rumen environment and the diet selected from feeds of different ED were investigated in two experiments. In the first experiment two feeds, L and H, and their mixture M (3:1 w/w) were formulated. All feeds had similar calculated metabolizable protein: metabolizable energy (ME) ratios, but differed in ED (7·4, 8·1 and 10·1 MJ ME$sol;kg fresh feed for L, M and H respectively). The feeds were offered ad lib. either singly or in paired choices (L/M, L/H and M/H; n6 per treatment) to growing sheep. Although the rate of live-weight (Lwt) gain on feed H was higher than on feeds L or M, and the daily rate of feed intake lower, the sheep on feed choices did not consume only feed H. Instead they selected a mixture of both feeds offered, such that the total amount of H consumed per kg fresh feed was similar on choices L/H and M/H. The rate of Lwt gain of sheep on choices L/H and M/H was not different from that achieved on feed H alone. In the second experiment the choice L/H was offered to fistulated sheep (10 months of age, mean Lwt 57·5 kg) in an 8×8 Latin square, with 7 d periods. Treatments were infusions into the rumen (total volume 1 litre) over 4 h on days 1–4 of each period of acid (HC1; Acid 1, 400; Acid 2, 300 and Acid 3, 200 mmol/l), alkali (NaOH; Alk 1, 316; Alk 2, 212 and Alk 3, 109 mmol/l) and control (NaCl; Con 1, 315 and Con 2, 209 mmol/l). Infusate osmolalities (mOs/kg) were 795 (Acid 1), 585 (Acid 2, Alk 1 and Con 1), 390 (Acid 3, Alk 2 and Con 2) and 200 (Alk 3). Infusion treatment significantly affected the diet selection of the sheep (P < 0·05) according to the osmolality of infusate, but not according to rumen pH. During infusions intake of feed H tended to decline with increasing treatment osmolality, whereas intake of L remained constant. The effects on diet selection and feed intake were of a short duration with no carry-over effects. These results show that sheep given a choice between two feeds of different ED select a substantial quantity of the low-ED feed; this diet selection is affected by short-term manipulations of their rumen environment, in a manner that is consistent with the maintenance of effective rumen conditions.

Although essential fatty acids (EFA) and their longer chain, more unsaturated derivatives play a major role during pregnancy, hardly any information is available with respect to the course of the maternal EFA status during an uncomplicated pregnancy and its relationship to the neonatal EFA status. Therefore, a longitudinal study was started in which 110 pregnant women gave repeated blood samples from the 10th week of gestation until delivery. After birth a blood sample from the umbilical vein and a maternal venous blood sample were collected as well, and 6 months after delivery a final blood sample from the mother was taken. The absolute (mg/l) and relative (% total fatty acids) amounts of the fatty acids in plasma phospholipids were determined. The total amounts of fatty acids increased significantly during pregnancy. This pattern was similar for the individual fatty acids and fatty acid families. The relative amount of linoleic acid (18:2n−6) did not change during pregnancy, whereas the relative amount of arachidonic acid (20:4n−6) decreased. Despite maternal mobilization of docosahexaenoic acid (22:6n−3, DHA), suggested by a temporary increase in the DHA status until 18 weeks gestation, the DHA status steadily declined thereafter. This pattern was associated with a progressive increase in the DHA deficiency index in maternal blood throughout pregnancy and resulted in a sub-optimal neonatal DHA status. The overall maternal EFA status also declined steadily during pregnancy. Therefore, the question arises whether the mother, under the prevailing dietary conditions, is able to meet the high fetal requirement for EFA.

The short-term kinetics of Zn turnover were studied in Irish setters with gluten-sensitive enteropathy and control dogs following intravenous injection of 0·25 mg 96·5% enriched 70ZnCl2. The 70Zn enrichment of serum was found closely to obey two-compartment kinetics and the derived two-compartment decay equation was used to calculate the size and turnover of the two initial rapidly exchanging pools of body Zn. In normal Irish setters isotopic Zn initially equilibrates with a pool (a) of size 1·27 (SD 0·46) μmol/kg and then with a second pool (b) of size 6·83 (SD 1·72) μmol/kg. The fractional turnover of pool (b) was approximately one eighth that of pool (a). Enteropathic dogs showed no reduction in the size of either rapidly exchangeable Zn pool, reduction in serum Zn concentration or abnormality in Zn balance and hence these results do not support the possibility of an underlying Zn deficiency in this disorder.

Dietary Mg restriction is generally considered to contribute to the prevention of struvite urolithiasis in cats, but its effects on faecal and urinary excretion of Ca and P have not been systematically investigated. The present study seeks to fill the gap. In a 4×4-week crossover study, ovariectomized cats were fed on purified diets containing either 0·40, 0·79,1·59 or 3·17 mmol Mg/MJ (0·19, 0·38,0·76 and 1·52 g Mg/kg diet). Increasing the dietary Mg level from 0·40 to 3·17 mmol Mg/MJ by the addition of extra MgCO3 raised urinary and faecal excretion of Mg from 0·14 to 0·68 mmol/MJ and from 0·28 to 1·66 mmoI/MJ respectively. The 8-fold increase in Mg intake significantly raised urinary excretion of Ca from 0·06 to respectively when the dietary Mg level was raised from 0·40 to 3·17 mmol/MJ. A dietary level of 0·40 mmol Mg/MJ (0·19 g Mg/kg diet) was found to be sufficient to maintain Mg balance in the adult ovariectomized cats fed on the purified diet.

The effects of dietary P restriction to half the recommended minimum level on growth, bone and renal mineralization and urinary composition were studied in female kittens. In two separate experiments, 8-week-old weanling kittens were fed on purified diets containing either 4·6 or 9·2 mmol P/MJ (2·8 or 5·6 g P/kg diet). In the second experiment there was an additional low-P diet in which the Ca concentration was reduced from 9·5 to 4·8 mmol/MJ (7·5 v. 3.8 g Ca/kg diet). P restriction slightly but systematically reduced weight gain (to a maximum of 16%) and growth of the tibia (by 1–4%); the former effect was statistically significant (P < 0·05) between the ages of 15 and 20 weeks in Expt 1 only, and the latter did not reach statistical significance at any time point (P g 0·13). No adverse effect of P restriction was found on mineralization of femur at the age of 39 weeks. Kidney Ca concentrations were significantly lowered (Expt 1, 6 v. 20/μmol/g dry weight, P < 0-001; Expt 2, 7 v. 16/μmol/g dry weight, P < 0-01) in cats fed on the low-P diets, this effect not being affected by the dietary Ca:P ratio. Urinary P concentration was significantly depressed (by 50–96%) after feeding the low-P diets (P < 0-001). P intake did not influence P, Ca and Mg retention during the period of 15 to 39 weeks of age.

The recovery of inulin, a naturally occurring β(2→l)-fructan isolated from Jerusalem artichoke (Helianthus tuberosus L.), in the small intestine of man was studied in ileostomy subjects. The ileostomists were given a low-dietary-fibre diet based on white wheat bread and virtually free of inulin, and the same diet with the addition of 10 g and 30 g inulin product respectively, and the recovery and mean transit time (MTT) of inulin were estimated by tracking inulin in ileal effluent. The recovery of inulin was approximately 87% at both ingestion levels. MTT was 4·9 (SE 0·6) h at an intake of 10 g inulin product decreasing to 3·4 (SE 0·3) h at an intake of 30 g Inulin product. A significant change in the fructose: glucose ratio of inulin from ingestion (4·1) to recovery in ileal effluent (4·5–4·7) and a lower recovery of the glucose residue than of the fructose residue of inulin indicate that the low-molecular-weight inulins are more sensitive to hydrolysis than the high-molecular-weight fragments. The loss of inulin during passage through the small intestine is presumably due to hydrolysis by either acids or enzymes and to microbial degradation by the microfiora permanently colonizing the distal small intestine. The concentrations of lactic acid (LA) and short-chain fatty acids (SCFA) in frequently collected ileal effluents on the control day were approximately 6 mmol/l and approximately 55 mmol/l respectively. During periods with inulin ingestion the concentration of LA increased to 18–26 mmol/l (P < 0·052), while the concentration of SCFA ran converse and decreased to 18–32 mmol/l (P < 0·023). The osmotic loads (68 and 204 mosmol/l) associated with the ingestion of inulin product caused minor malabsorption of low-molecular-weight sugars.

The effects of intraduodenal and dietary lipid on alertness, mood and performance in a task requiring sustained attention were investigated in two studies. The first experiment compared the effect of duodenal infusion of either 100 g/l Intralipid (8·36 kJ/min) or isotonic saline (9 g NaCl/l) in paired studies carried out on two non-consecutive days on five male volunteers. Two consecutive 3 h infusions, one of lipid, the other saline, were given blind on each day using a crossover design. Analysis of variance indicated that lipid significantly reduced alertness (P < 0·05) and affected the speed and accuracy of performance in a sustained attention task (P < 0·05). A second experiment compared the effects on eight male volunteers of two isoenergetic lunches of similar appearance, taste and protein content but differing fat and carbohydrate (CHO) contents (fat energy:CHO, 64:18 v. 7:76). Alertness was lower (P < 0·05) and responses to stimuli in a sustained attention task were slower after the high-fat meal than after the low-fat meal (P < 0·05). In conclusion, infusion of lipid into the small intestine, and the substitution of fat for carbohydrate while keeping energy and protein constant in a lunch, both cause an enhanced postprandial decline in alertness and concentration. This may be related to the presence of lipid in the small intestine.

There is limited information relating Ca intake to bone and height acquisition among Oriental children who consume little or even no milk. The present controlled study investigated the acquisition of bone mass and height of Chinese children with an initial Ca intake of approximately 567 mg/d who were supplemented to about 800 mg/d. Eighty-four 7-year-old Hong Kong Chinese children underwent an 18-month randomized, double-blind, controlled Ca-supplementation trial. The children were randomized to receive either 300 mg elemental Ca or a placebo tablet daily. Bone mass of the distal one-third radius was measured by single-photon absorptiometry, lumbar spine and femoral neck were determined using dual-energy X-ray absorptiometry. Measurements were repeated 6-monthly. Baseline serum 25-hydroxycholecalciferol concentration and physical activity were also assessed. Baseline Ca intakes of the study group and controls were respectively 571 (SD 326) and 563 (SD 337) mg/d. There were no significant differences in baseline serum 25-hydroxycholecalciferol concentration (P = 0·71) and physical activity (P = 0·36) between the study and control groups. After 18 months the study group had significantly greater increases in lumbar-spinal bone mineral content (20·9 v. 16. 34%; P = 0·035), lumbar-spinal area (11·16 v. 8·71%; P = 0middot;049), and a moderately greater increment in areal bone mineral density of the radius (7·74 0·600%; P = 0.081) when compared with the controls. The results confirm a positive effect of Ca on bone mass of the spine and radius but no effects on femoral-neck and height increase. A longer trial is warranted to confirm a positive Ca effect during childhood that may modify future peak bone mass.