1. Male, Sprague-Dawley (Charles-River) rats, of initial weight 272 g, were given a powdered stock diet (T1) ad lib. force-fed a synthetic diet (T2) or offered a range of palatable foods in conjunction with the powdered stock diet (T3) or a similar diet supplemented with certain minerals and vitamins (T4).

2. Metabolizable energy (ME) intake (kJ/d) averaged 303, 453, 402 and 383 for T1, T2, T3 and T4 respectively and corresponding weight gains were 5.5, 6.9, 8.2 and 7.9 g/d and were significantly different (P < 0.001).

3. The intakes of T3 and T4 rats ranged from 10 to 60% above the mean value for T1.

4. Crude protein (CP; nitrogen × 6.25) retentions were similar for T1, T3 and T4 rats and significantly lower (P < 0.01) for T2 rats. Fat retentions were 1.1, 4.1, 2.9 and 2.4 g/d for T1 to T4 respectively (P < 0.001).

5. The energy contents of the gain (MJ/kg) were 12.7, 26.0, 16.7 and 14.9 for T1 to T4 respectively (P < 0.001) and energy retentions (kJ/d) were 70, 179, 139 and 117 respectively (P < 0.001).

6. A linear regression of energy retention (ER) on ME yielded a slope of 0.78 and a mean energy requirement for zero balance of 510 kJ/kg body-weight0.75.

7. These results are in conflict with reports of ‘diet-induced thermogenesis’ in ‘cafeteria’-fed rats.

1. The energy metabolism of young pigs offered low-protein diets to appetite or a normal starter (diet 1, 225 g crude protein (nitrogen x 6·25; CP)/kg dry matter (DM)) to maintain zero energy balance was studied using indirect calorimetry and slaughter. The treatments were: T1, diet 1; T2, 46 g CP/kg DM; T3, 21 g CP/kg DM; T4, 17 g CP/kg DM; T5, 21 g CP/kg DM and no supplemental thiamin.

2. Daily heat production (kJ/d per kg body-weight (W)0·75) declined on all treatments from a pre-experimental value of 613. The greatest decline was observed in T1 pigs where the final value was 375.

3. There was a progressive reduction in energy intake from 5·4 MJ/d for T2 pigs to 3·0 MJ/d for T4 and T5 pigs (P < 0·001). The mean intake of T1 pigs was 2·3 MJ/d.

4. There were highly significant treatment differences (P < 0·001) in gain of live-weight and in the gain of carcass DM, CP, fat and energy.

5. There were marked treatment effects on body composition. T1 pigs showed a decrease in the proportion of carcass fat and an increase in the proportion of carcass CP during the experiment while the other four treatments caused large increases (P < 0·001) in carcass DM and fat content and no change in CP content. These changes resulted in large differences in the energy content of the gain, the mean values (MJ/kg) being 0·6, 35·5 and 88 for T1, T2 and T3 pigs respectively. T4 and T5 caused energy gain coupled with weight loss.

6. A linear regression of energy retention (ER; MJ/d per kg W0·75) on metabolizable energy (ME) intake yielded the equation

ER = 0·78 ME-0·365, r0·96.

7. These results indicate that heat production declines when the growth rate of young pigs is reduced either by restriction of energy or of protein intake. They do not support the suggestion that low-protein diets give rise to increased ‘diet-induced’ thermogenesis.

1. Female rats were given throughout pregnancy and lactation a semi-synthetic diet, in which the fat was provided entirely by a soft margarine rich in linoleic acid (18:2ω6) or by mixture of butter and lard, and the influence on the fatty acid composition of fetal and pup brain and retinal phosphoglycerides was studied.

2. The percentage of docosahexaenoic acid (22:6ω3) was much lower but that of docosapentaenoic acid (22:5ω6) was correspondingly higher in the brains of the day-22 fetuses and the 21-d-old pups from the margarine group compared with those from the group given the animal fats. Similar changes were noted in the synaptosomal and retinal phosphoglycerides, being most marked in the ethanolamine phosphoglycerides.

3. The remaining pups from two groups were weaned on day 21 post partum on to the same stock diet that contained preformed 22:6ω3. After 9 weeks of this diet, the differences between the two groups in the fatty acid composition of the brain phosphoglycerides were barely discernible. The percentage of 22:5ω6 had decreased and had been replaced by 22:6ω3.

4. It is concluded that the consequences of consuming a diet rich in linoleic acid and almost devoid of 22:6ω3 on brain fatty acid composition deserve consideration in man.

1. Newborn rabbits were over-fed by encouraging them to suck from two lactating does. These double-fed animals were compared with single-fed litter-mate controls.

2. Single- and double-fed rabbits were compared with respect to body-weight, bone length and weights of heart, kidney, lung, liver, spleen, stomach, brain and adipose lobes at ages 7, 14 and 21 d and at 25 weeks. Body composition with respect to fat, protein and water was also analysed in animals killed during the first month of life.

3. Double feeding had a profound effect on body-weight, such that by 21 d of age these animals weighed 65% more than controls. Longitudinal growth was also increased, but to a lesser extent. Organ weights were largely determined by body-weight with the exception of the brain which was unaffected by double feeding and the heart and adipose lobes which were represented to excess. Body composition studies demonstrated a marked increase in body fat and a decrease in body water as a percentage of body-weight in the double-fed.

4. When mature, double-fed rabbits weighed a little more than controls and had accumulated significantly more fat. No other difference between them was demonstrated.

5. Other experiments on rats, mice and pigs, along with these experiments on rabbits, suggest that young mammals respond to over-feeding with a limited increase in real growth associated with excess deposition of adipose tissue. Studies on infants of diabetic mothers have demonstrated that the human fetus responds to over-nutrition in a very similar way. Therefore we should be cautious about over-feeding human infants, especially premature ones, as it seems unlikely that excessive deposition of fat will be beneficial.

1. Children (405), initially of average age 11.5 years, recorded all food and drinks consumed for three consecutive days (with an interview on the fourth day) on five separate occasions over a 2-year period. Food tables (Paul & Southgate, 1978) enabled nutrient intakes to be calculated. The data collected were found to be of high reliability (Hackett et al. 1983).

2. The mean energy intakes showed broad agreement with other recent British dietary surveys but were well below those recorded in the prewar study by Widdowson (1947) and the FAO/WHO (1973) recommended levels. They were slightly below the current Department of Health and Social Security (DHSS; 1979) recommended intakes.

3. Over the 2-year period, the energy intake of the boys increased by 13% compared with an increase of only 7% in the girls.

4. The iron and vitamin A intakes of all groups of children were low compared with current recommendations (DHSS, 1979). This seems to be a result of falling energy intake. Mean calcium intakes were also only marginally in excess of the recommended intake, and those of most of the girls would fall below the recommendation if the proposal to end the fortification of flour (DHSS, 1981) is implemented.

1. Protein utilization was determined by assay with low-protein diets limiting in one of nine essential amino acids. The diets contained 50 g protein/kg and the amino acid score of the protein was 0.50.

2. Protein utilization was found to be related to the particular limiting essential amino acids present.

3. The usefulness of Bender's (1965) standard amino acid requirement for the estimation of amino acid utilization from a low-protein diet is discussed.

1. To investigate the role of dietary components in the hyperinsulinaemia of the obese hyperglycaemic (ob/ob) syndrome, plasma insulin responses to fasting and refeeding were examined in Aston ob/ob mice supplied with standard diet, non-digestible-carbohydrate test food, and isoenergetic test foods from which either carbohydrate, protein or fat was omitted.

2. During fasting, plasma insulin concentrations fell more rapidly and to a greater extent than plasma glucose. Refeeding the standard diet raised insulin concentrations above normal, associated with a 25% compensatory increase in food intake over 24 h.

3. Test foods supplied to previously fed or fasted mice produced glucose responses consistent with the available carbohydrate content. Carbohydrate-free food (protein and fat) provided a small insulinotropic stimulus; the effect of protein-free food (carbohydrate and fat) was greater; and the combination of carbohydrate with protein (fat-free food) evoked a marked insulin response. In contrast, insulin concentrations declined in mice given the non-digestible-carbohydrate food.

4. Consumption of the standard diet was increased after 24 h feeding non-digestible-carbohydrate food, but was unaffected by a 30 h fast initiated 54 h previously.

5. These results demonstrate that hyperinsulinaemia in ob/ob mice is not merely triggered by the ingestion of bulk, but depends on the type of nutrient ingested. Dietary carbohydrate appears to be the major stimulus to the hyperinsulinaemia, with an important augmentation in the presence of protein. Since direct glucose stimulation of insulin release is defective in ob/ob mice, the hyperinsulinaemia must be mediated by increased activity of the enteroinsular axis.

1. Protozoa-free steers with simple rumen and abomasal cannulas were given basal diets consisting of a concentrate mixture of flaked maize and tapioca with barley straw (BS) or alkali-treated barley straw (BSA). Other diets were supplemented with urea (BSU and BSAU respectively) or with fish meal replacing the tapioca (BSF and BSAF respectively). The diets were isoenergetic and calculated to provide sufficient metabolizable energy (ME) to support a growth rate of 0.5 kg/d. Rumen-degradable nitrogen (RDN): ME values (g/MJ) were estimated to be 0.50, 1.20 and 0.80 for the basal diet, urea- and fish-meal-supplemented diets respectively. RNA and α, ε-diaminopimelic acid (DAP) were used as microbial markers. 103Ruthenium and polyethylene glycol (PEG) were given as flow markers and flows (g/24 h) at the abomasum of organic matter (OM) and nitrogenous constituents were calculated.

2. Samples of mixed bacteria separated from rumen digesta from animals receiving N-supplemented diets contained significantly more N than those from animals receiving basal diets (approximately 74 and 62 mg/g dry matter (DM) respectively) but there were no other significant differences in total-N contents between treatments. RNA-N: total-N values were similar for all diets (approximately 0.13). DAP-N: total-N values were significantly lower in bacteria from animals receiving alkali-treated (AT) rather than untreated (UT) straw (approximately 0.008 and 0.011 respectively).

3. The proportion of OM intake digested in the rumen (ADOM) was significantly higher for animals receiving AT straw rather than UT straw (approximately 0.54 and 0.43 respectively). N supplementation had no effect on OM digestibility.

4. When basal rather than N-supplemented diets or AT-straw- rather than UT-straw-containing diets were given, there were significantly lower flows of ammonia-N, non-ammonia-N (NAN) and microbial-N (based on RNA flow, MN(RNA)) at the abomasum. Mean daily MN(RNA) flows (g) were 21, 30, 31, 16, 27 and 28 for diets BS, BSU, BSF, BSA, BSAU and BSAF respectively. These correspond to estimated efficiencies of microbial protein synthesis, expressed as g MN(RNA) /kg truly-digested OM, at 14, 22, 22, 12, 18 and 19 respectively. Values were significantly lower for basal as compared with corresponding N-supplemented diets and for AT-straw diets as compared with corresponding UT-straw diets.

5. Estimated mean proportions of total feed-N intake degraded in the rumen, based on MN(RNA) as microbial marker, of diets BS, BSU and BSF were 0.60, 0.74 and 0.47 respectively; corresponding values for diets BSA, BSAU and BSAF were 0.72, 0.73 and 0.36 respectively. Making certain assumptions, the mean proportions of fish-meal-N digested in the rumen were calculated to be 0.23 and 0.14 respectively for UT- and AT-straw diets. The values were not significantly different. Values for microbial flows based on DAP as marker were significantly lower, by about 25%, than those based on RNA.

1. The volume and number of adipocytes were measured in fourteen anatomical sites of adult guinea-pigs kept in small cages and fed ad lib. kept in small cages and on restricted diet or fed ad lib. and exercised.

2. In the sedentary ad lib.-fed animals, there was no significant correlation between percentage body-weight as adipose tissue, as determined by direct dissection, and mean adipocyte volume based on samples from many different sites. The correlation was significant, though not high, for sedentary, restricted-diet animals and for exercised specimens.

3. The correlations between the volume of adipocytes from left–right pairs of sites, and from sites around the same limb, were highly significant under all conditions studied. The correlation between the volume of adipocytes from sites other than left–right pairs of sites was weaker and in some cases statistically insignificant in sedentary ad lib.-fed guinea-pigs. The volume of adipocytes from sites in the groin region, the mesenteries and medial to the trapezius muscle failed to correlate in many cases with the volume of adipocytes from other sites sampled.

4. The number of adipocytes at each site was similar in the exercised and sedentary ad lib.-fed animals. The restricted-diet, sedentary group had fewer adipocytes at all sites studied except the omental and mesenteric fat mass and the groin sites.

5. It is suggested that moderate regular exercise or fasting gives rise to closer coordination between adipocytes at different sites because central factors regulating adipocyte volume become more prominent than local factors.

1. Retinol esterification in the small intestine, liver and kidney of rats given a normal diet or a vitamin-A-free diet and of rats given large doses of vitamin A was studied. The active enzyme is a microsomal acyl CoA: retinol acyl transferase (ARAT).

2. In the small intestine ARAT activity was 0.37 nmol ester/mg microsomal protein per min. Large doses of vitamin A increased the activity significantly, while the enzyme activity in the vitamin-A-deficient rats was in the range of that of the controls. Retinoic acid in physiological doses (0.064 mg three times per week) had no influence on ARAT activity.

3. In the liver, ARAT activity of the controls was 0.58 nmol ester/mg microsomal protein per min. The activity was increased after large doses of vitamin A. It was not significantly reduced in vitamin-A-deficient animals.

4. The kidney had a low, but significant ARAT activity, both in normal and vitamin-A-deficient animals and after large doses of vitamin A (range 0.08–0.14 nmol ester/mg microsomal protein per min).

5. The vitamin-A-esterifying enzyme in the small intestine and liver of the rat seems to be influenced by the amount of retinol in the diet.

1. Two intermuscular adipose depots, the popliteal mass (POP) and the fat under the gluteus superficialis muscle (GLS) were studied in guinea-pigs maintained under three different regimes of diet and exercise.

2. Eleven different sites in POP and four sites in GLS were defined using associated muscle and fascia as ‘landmarks’. Samples of twenty to twenty-five adipocytes from each site were removed and their mean volume measured; a consistent pattern of distribution of larger and smaller adipocytes within POP and GLS was found in all animals.

3. The correlation between the volume of adipocytes from sites between the same pairs of muscles was substantially greater than the correlation between the volume of adipocytes from comparable sites between different muscles, whether the sites were within the same fat mass (POP) or in different fat masses (POP and GLS).

4. The volume of adipocytes from the edge of the fat mass correlated more closely with those from the edge of the same or a synergistic muscle than with the volume of cells from the centre sites or edge sites from an interface with another muscle. These effects were most pronounced in exercised animals and weak or insignificant in sedentary ad lib.-fed animals.

5. The volume of adipocytes from edge sites correlated with the gross weight of the adjacent muscles in exercised animals only.

6. It is concluded that muscle activity has a local effect on the volume of adjacent adipocytes. It is suggested that the mechanism involved is mechanical rather than biochemical.

1. The availability of lysine in nine vegetable-protein concentrates was assessed using the slope-ratio assay for growing pigs and rats. Diets were equalized for crude fibre using solka floc to minimize any possible effects of variation in fibre content on availability estimates.

2. The availability of lysine in the nine proteins for pigs, using food conversion efficiency (FCE) on a carcass basis as the criterion of response were (proportion of total): cottonseed meal 0.39, lupin (Lupinus angustifolius) seed meal no. 10.37, no. 20.65, no. 30.54, no. 40.54, field peas (Pisum sativum) 0.93, peanut (groundnut) meal 0.57, soya-bean meal no. 10.98, no. 2 0.89.

3. Estimates of available lysine for rats as assessed by the slope-ratio assay using FCE on a carcass basis were in close agreement with the pig estimates for cottonseed meal (0.35) and soya-bean meal no. 1(0.91) and no. 2(0.89), higher for lupin-seed meals (range 0.70–0.94 with a mean of 0.81) and peanut meal (0.76) and lower for field peas (0.76).

4. The differences in available lysine were not detected by the chemical Silcock available-lysine test (Roach et al. 1967) or by the direct 1-fluoro-2,4-dinitrobenzene procedure (Carpenter, 1960).

1. The present study was done to clarify the relationship between the amount of dietary protein given to, and the gut microflora of, the host. Day-old chicks were given diets containing three concentrations of dietary protein (50, 200 and 400 g/kg) for 14 d. Body-weight gain, food consumption, body consumption, and protein and energy utilization were measured.

2. There was no difference in body-weight gain and food consumption between germ-free (GF) and conventional (CV) chicks, but food conversion efficiency (g body-weight gained/g food consumed) was significantly higher in GF than in CV chicks.

3. Little difference was found in protein retention (g protein retained/14 d), but protein retention rate (g protein retained/g protein consumed) tended to be higher in GF chicks, particularly those given the diet with the lowest protein.

4. The presence of micro-organisms improved metabolizable energy (ME) values of the diets, but not all of the digested energy in CV chicks was utilized for growth. Therefore there was little difference in energy retention (kJ energy retained/14 d) between environments, although energy retention rate (kJ energy retained/kJ ME consumed) was significantly lower in CV chicks. The amount of body fat in GF chicks was higher than that in CV chicks, especially in those fed on the low-protein diet.

5. It is suggested that although the gut microflora may have beneficial effects on the digestion of dietary energy components, they may have detrimental effects on utilization of ME by their hosts, because chicks harbouring a gut microflora seem to have higher energy requirements for maintenance.

1. The effects of feeding meals, in amounts equivalent to ad lib. intake or to 75% and 50% restriction by intubation, were studied in chicks.

2. Growth estimated by body-weight gain and shank length was improved by tube feeding in the 50%-restricted chicks.

3. Tube feeding increased energy retention at all feeding levels and nitrogen retention in the restricted chicks only.

4. Body fat was increased in the full-fed chicks by intubation and decreased in the 50%-restricted chicks only.

5. Crop and gizzard weights were increased by food restriction and by intubation. Tube-feeding increased the weight of the small intestine at all feeding levels.

6. The activities of the digestive enzymes were lower in the pancreas and higher in the small intestine of the tube-fed chicks than in the voluntarily-fed ones at all feeding levels.

7. It is suggested that synthesis, secretion and stablity of the different pancreatic enzymes could be affected diversely by feeding regimens.

1. Volatile fatty acids (VFA) absorption in the large intestine of the anaesthetized rabbit was evaluated by measuring variations in the concentration of VFA in intestinal loops and plasma arteriovenous differences. Metabolic conversions were studied using [1-14C]acetate, [1-14C]propionate and [3,4-14C]butyrate.

2. The hind-gut tissues metabolized the three VFA, although this metabolism varied with the segment studied. Butyrate was the best respiratory fuel for the colonic wall, followed by propionate; acetate participated also, but it was mainly converted to glutamate.

3. The liver was the main organ metabolizing absorbed propionate and butyrate; acetate was available for extrahepatic tissue metabolism.

4. For the rabbit, VFA represented about 40% of the maintenance energy requirement.

1. Two groups of children with phenylketonuria (PKU) received protein at two different levels. The protein scource was a protein hydrolysate, devoid of phenylalanine, and intact protein from milk, vegetables and fruit. One group (RDA group) was given protein at a level based on the recommendations of the (US) Food and Nutrition Board (1974, 1980). The other group (FAO group) was given protein at the level of intake corresponding to the Joint FAO/WHO ad hoc Expert Committee (1973) safe levels of intake of egg or milk protein. The children were monitored very closely for several years. From an earlier study evaluating the protein intake of the two groups it was suspected that the Joint FAO/WHO ad hoc Expert Committee (1973) recommendations were marginal.

2. In the present study the phenylalanine intake of the two groups required to maintain the plasma phenylalanine concentration at the required level was established. The results showed that the RDA group required more phenylalanine than the FAO group. This difference was statistically significant from the age of 5–15 months.

3. We have interpreted the greater requirement for phenylalanine in the RDA group as a result of a greater nitrogen intake and thus a more rapid chemical maturation of N (increase in protein concentration of the body with age). It is known that up to the age of 6 months the chemical maturation of N is related to the N intake. In the present study we have found that this difference in chemical maturation lasted up to the age of 15 months. The conclusion drawn from the study was that a protein intake slightly higher than the Joint FAO/WHO ad hoc Expert Committee (1973) recommendations might be desirable.

1. Groups of rainbow trout (Salmo gairdneri) (mean weight 14 g) were given diets containing 0.8, 1.3, 2, 3, 4 or 6 g tryptophan/kg diet for 12 weeks.

2. By analysis of the growth results, the dietary requirement of tryptophan was found to be 2.5 g/kg diet (equivalent to 50 mg/kg biomass per d).

3. Carbon dioxide expired by trout following intraperitoneal injection of [14COOH]tryptophan contained little radioactivity when dietary tryptophan level was low but, above 2.0 g/kg diet, it increased rapidly with increasing dietary tryptophan level. The break point in the dose-response curve did not, however, coincide with that from the growth results.

4. Changes in concentrations of free tryptophan in blood and liver and activity of hepatic tryptophan pyrrolase (EC 1.13.11.11) in response to changes in dietary tryptophan concentration did not provide reliable indicators for quantifying dietary requirement. Unlike the situation in mammals, blood tryptophan was not protein-bound to any appreciable extent. Tryptophan pyrrolase of trout has properties which suggest it has no apoenzyme form.

5. In fish given adequate levels of tryptophan injected intraperitoneally with a tracer dose of [14COOH]tryptophan, 60% of the dose was incorporated into body protein within 1 d. The turnover of the label in this protein is very slow.

6. Those trout given diets deficient in tryptophan suffered from severe scoliosis and lordosis as well as having increased liver and kidney levels of calcium, magnesium, sodium and potassium.

1. Four steers were given straw and tapioca diets, twice daily, in a 4 x 4 Latin-square design. These diets, containing 4.2 g nitrogen/kg dry matter (DM), were further supplemented with either urea, decorticated groundnut meal (DCGM), untreated (UT) casein or formaldehyde-treated (FT) casein to give a total of 19.7 g N/kg DM and 10.5 MJ/kg DM daily.

2. Concurrent samples of rumen bacteria and protozoa and abomasal digesta were collected for each period of the experiment and the concentrations of 2-aminoethyl phosphonic acid (AEPA), diaminopimelic acid (DAPA), total nitrogen (TN), total phosphorus (TP), amino acids and hexosamines were determined in the dried preparations. The nature of the dietary supplements had little effect on the concentrations of most of these constituents or on the total protozoal numbers.

3. Abomasal digesta samples marked with polyethylene glycol (PEG) and chromic oxide for flow estimation were collected over 24 h, and the proportions of protozoal-N, bacterial-N and microbial-N estimated simultaneously using the markers AEPA, DAPA and RNA respectively. These digesta-N components were also estimated using an amino acid profiling (AAP) method which gave, in addition, estimates of the dietary and endogenous components. For the diets containing casein, the proportion of dietary casein was estimated directly using casein-P as a marker.

4. Estimates of the respective mean proportions of microbial-N in abomasal digesta non-ammonia-N (NAN) for the diets containing urea, DCGM, UT casein or FT casein were: AEPA 0.56, 0.32, 0.27 and 0.16; DAPA 0.88, 0.70, 0.81 and 0.57; RNA 0.98, 0.85, 0.92 and 0.53.

5. Giving FT casein significantly (P < 0.001) increased the flow of casein-N at the abomasum and a significantly (P < 0.001) greater proportion of casein-N was found in abomasal NAN (0.51 v. 0.09) where FT rather than UT casein was given.

6. The AAP method gave results for the proportions of microbial- and dietary-N (where casein was given) which were, in general, slightly lower than those obtained using RNA and casein-P as markers. Agreement with estimates of bacterial protein (from DAPA) and of protozoal protein (from AEPA) was less satisfactory.

7. Comparisons of the various estimates of the proportions of microbial-N in abomasal digesta suggested that the results obtained for protozoal-N by AEPA were overestimates. AEPA was found in mixed rumen bacteria which may have accounted in part for these overestimates. However, AEPA was not detected in any of the dietary ingredients.

1. Groups of rainbow trout (Salmo gairdneri) of approximate mean initial weight 8 g were grown in outdoor tanks over a 14-week period at water temperatures between 12° (start) and 6° (end). Four diets were used. Two contained non-oxidized fish oil (120 g/kg) with or without supplementary DL-α tocopheryl acetate and two contained moderately oxidized fish oil again with or without DL-α-tocopheryl acetate. The measured selenium content of the diets was 0.10 mg/kg.

2. No significant differences occurred as a consequence of the use of moderately oxidized oil compared with the corresponding treatments using non-oxidized oil. Significant differences did occur between dietary treatments that contained supplementary DL-α-tocopheryl acetate and those that did not. These differences applied to weight gain, haematocrit, erythrocyte fragility, mortalities, liver and muscle tocopherol concentrations and lipid peroxidation of liver mitochondria in vitro. Liver glutathione peroxidase (EC 1.11.1.9) activity was unaffected by the dietary treatments used and the proportions of fatty acids in polar lipids of liver and muscle were little changed by the diets used. Severe muscle damage occurred in trout given diets lacking supplementary DL-α-tocopheryl acetate.

3. Previous experiments carried out on rainbow trout at a constant water temperature of 15° (Hung et al. 1981; Cowey et al. 1981, 1983), using diets lacking supplementary vitamin E, did not lead to differences in weight gain, pathological changes or mortalities.

4. Vitamin E requirement may increase as water temperature decreases; minimum dietary requirements for vitamin E measured at a constant water temperature of 15° may not be valid under practical conditions where water temperatures vary over the year.

1. The effects of dietary phosphorus and sulphaguanidine levels, and sex differences on: (a) phytate digestibility, (b) calcium and P utilization, (c) the activities of alkaline phosphatase (EC 3.1.3.1), alkaline phytase (EC 3.1.3.8) and acid phosphatase (EC 3.1.3.2) in the intestinal mucosa of male and female rats were investigated.

2. There was a linear increase in femur ash, Ca and P contents and the maximum force withstood by the fresh femurs as dietary P level was increased from 1.5 to 3.0 to 4.5 g/kg diet.

3. The apparent digestibilities of Ca, P and phytate-P decreased as the level of P in the diet increased. Rats given the diets with 1.5 or 3.0 g P/kg were hypercalciuric and hypophosphaturic compared with rats receiving 4.5 g P/kg diet.

4. The level of Ca retained was similar for all treatments. The level of P retained increased as the dietary P level increased. This suggests that P deprivation was a result of inadequate amounts of P retained and not due to the absorption of inositol phosphates formed during the enzymic hydrolysis of phytate.

5. The addition of sulphaguanidine increased phytate digestibility without changing the activities of acid and alkaline phosphatase or alkaline phytase of the intestinal mucosa. This suggests that these enzymes did not play a role in the increase in phytate digestibility. However, dietary sulphaguanidine enhanced phytate digestibility, suggesting that alterations in the diet which modify either the composition or metabolism of the gastrointestinal microflora may be beneficial in enhancing the in vivo hydrolysis of phytate.

6. Differences between males and females are reported and discussed.