1. Male guinea-pigs were assigned to four different groups at birth. The heaviest group of animals was severely undernourished from 21 d of age (weight gain: 1.2 g/d v. 10 g/d for normally-fed animals).

2. At 35, 45, 55 and 65 d of age in normally-fed animals, and at 45 and 55 d of age in undernourished animals, blood testosterone levels were determined by radioimmunoassay, epididymidal tissue examined for the presence of spermatozoa and testes sectioned for rating of spermatogenesis using light microscopy.

3. Sexual maturity in terms of potential fertility (spermatozoa in the epididymis) was reached by all normally-fed animals between 45 and 55 d of age. High birth-weight animals had a higher incidence of the most advanced stages of spermatogenesis than low birth-weight ones at the various ages studied. In the undernourished animals spermatogenesis was clearly delayed.

4. Plasma testosterone concentrations were already in the adult range at 35 d and independent of age and birth-weight. The undernourished animals, however, had very low levels. Maintenance of spermatogenesis seemed compatible with low plasma levels of testosterone.

5. It is concluded that the timing of testicular development seems to be determined by the time the animals are born and appears to be unaffected by severe undernutrition from 21 d of age.

1. Rats were given low-fat diets for 3 d in which the carbohydrate source was starch. The livers of animals given the fructose or sucrose had increased hepatic activities of the fatty acid synthetase and stearoyl CoA desaturase (EC 1.14.99.5) enzyme complexes: in those given fructose there was a lower activity of the enzymes in adipose tissue.

2. Similar results were obtained in rats given fructose diets for 30 d, but in animals which had previously been made diabetic with streptozotocin, the activities were lower. The dietary treatment made little difference to the fatty acid profiles of the tissue lipids. The diabetic condition on the other hand produced considerable changes in fatty acid profile.

3. With diets containing approximately 200 g fat/kg in the form of butter or of polyunsaturated margarine, the tissue lipids from rats given sucrose had less linoleic acid than those from rats given starch. In addition, there was the expected difference between the rats given butter or margarine. The results are discussed in relation to the current literature.

1. The amount of manganese in nationally-representative samples of prepared and cooked goups of foods, and in a wide variety of individual foods, was determined by atomic absorption spectroscopy.

2. The average British diet was calculated to provide 4.6 mg Mn/d of which half was derived from tea and other beverages, 30% from cereals, and 15% from vegetables and fruit. Animal products provided little Mn.

3. Individual foods other than tea which were particularly rich in Mn in Britain were unrefined and partially-refined cereals, and some spices and herbs. Some vegetables and fruit, coffee, wine, chocolate and brown sugar also contained significant amounts of Mn.

1. Rat sucklings (18-d-old) bred from vitamin B12-deprived dams were compared with vitamin B12-suplemented dams’offspring, which were considered normal rat sucklings.

2. The vitamin B12-deficient rat sucklings had lower body-weight, liver weight and brain weight.

3. Vitamin B12 deficiency was also evident from the tenfold lower concentrations of vitamin B12 in liver and cerebellum.

4. The concentration of liver lipid was markedly increased in vitamin B12-deficient rats; triacylglycerol accounted for most of the increase. In brain the lipid concentration was slightly decreased (P < 0.05).

5. The methylation of ethanolamine phosphoglyceride to choline phosphoglyceride was reduced in both liver and brain in vitamin B12-deficient rats, as measured after the administration of [14C]ethanolamine. A slight decrease in choline phosphoglyceride concentration could be a consequence of this finding. The composition of phospholipids was otherwise normal.

6. Odd-chain fatty acids (pentadecanoate and heptadecanoate) accumulated in both liver and brain of the vitamin B12-deficient rat sucklings and constituted approximately 1% of total fatty acid.

7. The biosynthesis of fatty acid and cholesterol from intraperitoneally-injected 3H2O and [14C]propionate was unchanged in vitamin B12 deficiency.

1. The growth of muscle fibres was analysed by light microscopy in biopsies from subjects when malnourished, during nutritional rehabilitation, and after clinical recovery.

2. Muscle fibres from malnourished subjects were extremely atrophic (cross-sectional area, 110μm2). The fibres doubled in size during the early period of rehabilitation. Growth of muscle fibres during later periods of rehabilitation occurred at a slower rate.

3. The absolute rates of change in fibre sizes differed considerably between subjects, but the rates of change relative to the rate of gain of total body-weight (expressed as % recovery or % expected weight-for height (Nelson, 1975)) were similar between subjects after the initial growth spurt. The pattern of recovery appeared to differ between older and younger subjects.

4. Fibre sizes correlated with body-weight but not with age in the malnourished subjects. A significant correlation between fibre areas and either weight or age was observed during rehabilitation and after clinical recovery.

5. Fibre sizes of clinically-recovered subjects (mean age, 13.8 months; weight, 8.7 kg) were only approximately 60% of that for a well-nourished 6-month-old control subject (6.4 kg). These results suggest that a longer period of time is required for fibres to reach their expected size. Therefore, when the child has regained body-weight to that of a normal child of the same height, his muscles have not yet recovered and his body composition is abnormal.

1. The present study was considered as a first step to develop a method to measure food iron absorption from realistic common meals prepared and consumed by the subjects themselves in their own homes. The absorption of Fe from the meals was measured by means of the extrinsic-tag method modified to allow for a free choice of food items.

2. The mean Fe intake was 2.79 mg and the mean Fe absorption approximately 0.30 mg. The Fe status of the subjects corresponded to 31.5% absorption from a reference dose solution containing 3 mg elemental Fe as ferrous ascorbate. The variation in food Fe absorption obtained in this field study was found to be of the same magnitude as that obtained in studies performed under more controlled conditions as in the laboratory.

3. The conclusion was drawn that the proposed method could be used in realistic field studies aimed at, for example, explaining or preventing a high prevalence of deficiency. A sufficiently long run-in period and a careful instruction of the subjects was considered essential for the design of future field studies.

1. An epidemiological study of iron status in general practice has been undertaken. An age-sex register was established and a 10% stratified random sample (194 males and 220 females) of the patients above the age of 15 years was studied. A full blood count, serum Fe concentration, transferrin saturation and serum ferritin concentration were measured and correlated with clinical features associated with Fe deficiency.

2. The geometric mean for serum ferritin for males was 77 μg/1 (20–196 μg/1) and for females 37 μg/1 (8–177 μg/1). A low serum ferritin (male < 30 μg/1, female < 20 μg/1) in the absence of anaemia was found in fifteen males and thirty-five females. In this group forty patients had clinical features which are aetiologically associated with Fe deficiency. The incidence of similar features in a control group of thirty-three patients was seven.

3. It is suggested that this is indirect evidence that serum ferritin concentration is the most sensitive monitor of Fe status enabling the detection of pre-anaemic Fe deficiency.

1. The efficiency of utilization of the dietary energy and nitrogen contained in a dried lucerne (Medicago sativa cv. Chartainvilliers) given either chopped (CL) or ground (1.96 mm screen) and pelleted (PL), was measured in a comparative slaughter experiment. Growing lambs were given equal amounts of digestible energy in the chopped or pelleted form at each at each of the three planes of nutrition for a period of 100 d.

2. The initial energy, fat and protein content of both the carcass and the total body of the test lambs was estimated from regression equations between fasted (18 h) live weight and these components, derived from a group of twenty-three comparable lambs. The final energy, fat and protein content of the test lambs was determined directly by chemical analyses.

3. The metabolizable energy (ME) content of the diets was derived at each plane of nutrition from measured faecal and urinary losses and estimated methane losses. The depression in ME content with grinding and pelleting the dried lucerne was small (CL 8.69 MJ/kg dry matter (DM), PL 8.42 MJ/kg DM).

4. The efficiency of utilization of the ME of the dried lucerne for growth and fattening was higher (P < 0.01) when given in the ground pelleted form (0.533), than in the chopped form (0.284). The net energy value of the PL (3.5 MJ/kg DM) was higher than that of CL (2.2 MJ/kg DM).

5. Thus lambs fed on PL grew faster and had a higher caracass weight gain, carcass protein and fat retention than lambs fed on CL. The composition of the carcass was not altered by the physical processing treatment.

6. Digestion studies with these same CL and PL diets had shown that grinding and pelleting depressed digestion in the forestomachs and increased digestion in the small intestine compared with the chopped form. The increased efficiency of utilization of the gross energy and ME and the higher net energy value of PL was attributed primarily to a change in the site of digestion within the alimentary tract. Associated with this change was a higher value for absorbed amino acids : absorbed energy and an increased apparent absorption of methionine for lambs fed on PL. The difference in the energy costs of eating and ruminating the CL and PL was small.

1. Ten calves (50–58 kg live weight) were given a diet consisting of diluted whole milk, wheat gluten and supplemented with appropriate nutrients including amino acids but deficient in lysine. The lysine requirements of these calves, which were growing at approximately 0.25 kg/d, were estimated from responses to lysine supplementation of this diet. From plasma urea, plasma lysine, nitrogen retention and apparent digestibility of N responses the estimated lysine requirements were 8.5, 7.5, 7.2 and 7.6 g/d respectively.

2. From the mean lysine requirement (7.8 g/d) and the ratio, lysine: other essential amino acids in carcasses of similar calves the estimated requirements were (g/d): methionine 2.1, cystine 1.6, threonine 4.9, valine 4.8, isoleucine 3.4, leucine 8.4, tyrosine 3.0, phenylalanine 4.4, histidine 3.0, arginine 8.5, tryptophan 1.0.

1. In five experiments, involving 142 female pigs weighing on average 33 kg, estimates were made of the amounts of essential amino acids which minimized urinary N excretion when diets with barley as the only source of protein were given at the rate of 120 g/kg0.75 per d.

2. With additions of lysine (4.0 g/kg diet) and threonine (1.2 g/kg diet) to barley urinary N excretion decreased from 0.91 to 0.36 g/kg0.75 per d, corresponding to an increase in biological value (BV) from 0.51 to 0.86.

3. With these additions of lysine and threonine, there were no responses to additions of tryptophan, methionine or isoleucine, or to further additions of lysine or threonine, but addition of histidine significantly reduced N excretion.

4. No optimal addition of histidine could be determined; the mean rate of N excretion after addition of histidine (not less than 0.3 g/kg diet) was 0.27 g/kg0.75 per d, corresponding to a BV of 0.93.

5. There was a variation between pigs from different litters in their responses to added histidine. Those with low rates of N excretion on the unsupplemented diet did not respond to additions of histidine, but those with high rates did.

6. It is concluded that additions of only three amino acids can greatly improve the nutritive value of barley protein for the growing pig and that the amino acid composition of the supplemented protein closely approaches the ideal; it is also similar to whole-body tissue protein.

1. Thirty-three diets were made by adding to ground barley combinations of L-lysine (0–6.0 g/kg) and L-threonine (0–3.0 g/kg), together with vitamins and minerals. Each was given to two female and two castrated male pigs during their growth from 25 to 60 kg.

2. Growth rate increased from 0.36 kg/d to a maximum of 0.65 kg/d with additions of 3.8 g L-lysine/kg and 1.8 g L-threonine/kg; these values and the maximum gains achieved were slightly higher for castrates than for females. Minimum values for food conversion ratio of 2.84 for castrates and 3.06 for females were achieved with similar amino acid additions to those giving fastest growth.

3. Carcass fat, estimated by specific gravity, was least with the addition of 5.9 g L-lysine/kg, but continued to decrease up to the highest threonine concentrations. Backfat thickness was also reduced by amino acid additions but failed to reach a minimum.

1. The Streptococcus zymogenes assay procedure was modified and used in the estimation of available methionine and relative nutritional value in rice (Oryza sativa L.), sorghum (Sorghum vulgare Pers.), barley and field beans (Vicia faba L.). The results were assessed in relation to the content of tannins and ‘dye-binding lysine’, and to published information on the nutritional quality of some of the test samples.

2. In grain of ten varieties of sorghum, for which other workers had reported a correlation (r — 0.82; P < 0.01) between tannin content and amino acid digestibility in chicks, the available methionine content ranged from 6.3 to 17.7 g/kg protein (nitrogen × 6.25) and was highly correlated with tannin content (r — 0.97; P < 0.001). The content of total methionine and dye-binding lysine varied little between varieties and was not related to tannin content.

3. In nine samples of rice the availability of methionine was uniformly high, in accordance with literature values for true digestibility of the N.

4. In field beans the presence of tannins in the seed coat was associated with a significant (P < 0.001) reduction in the availability of methionine. In eleven tannin-free varieties the coefficient of availability averaged 0.791, compared with 0.685 in eleven tannin-containing varieties. The standard deviation associated with both values was 0.04. There was no such difference between the corresponding dye-binding lysine values.

5. Thirty-three samples of barley were examined, representing fourteen varieties, four of which had been grown at several widely different latitudes in England and Sweden. There was little difference in methionine content between samples. The average availability coefficient for eighteen samples grown in England was 0.995 ± 0.044, and for fifteen varieties grown in Sweden it was 0.851 ± 0.042. The difference was not associated with any difference in tannin content, which was uniformly low. The findings contradict published evidence for marked increase in tannin content with increase in geographical latitude of cultivation, associated with decrease in digestibility of N.

1. Dairy heifers given concentrates including vitamin A and wheat straw from 7 to 17 months of age had an average plasma β-carotene concentration of 20–60 μg/1. Control heifers given the same diet but supplemented with β-carotene had a β-carotene plasma concentration of 630–2190 μg/1.

2. In contrast to previous findings no differences in duration of standing oestrus, length of oestrous cycle, plasma progresterone and luteinizing hormone (LH) concentrations and interval between LH peak and ovulation were observed between the groups. All the heifers conceived after one or two inseminations; conception rate being 69% for heifers given a diet free of β-carotene and 78% for the controls.

3. Average rate of growth of heifers not supplemented with β-carotene was 0.75±0.02 kg/d v. 0.81±0.02 kg/d for the controls (P < 0.02).

4. The possible reasons for the discrepancy between present and previous findings are discussed.

1. Young pigs were fed on three diets consecutively, each diet being given for 1 week. The diets were given in random order as (g pig feed/kg body-weight): (a) 20, (b) 60, (c) 20 plus a supplement with the energy equivalent of 40 g pig feed/kg. The supplements included desiccated coconut, fish meal and glucose.

2. At the end of each week resting metabolic rate, beginning 12–14 h after feeding, was measured overnight using an open-circuit respiration chamber at thermoneutrality.

3. The oxygen consumption of pigs on the 60 g/kg diet was always higher than on the 20 g/kg diet. The addition of desiccated coconut, or fish meal also increased metabolic rate; whereas with added glucose, O2 consumption tended to be even lower than on 20 g/kg alone.

4. The administration of the β-blocker propranolol to pigs on ad lib. food intake reduced the rate of overnight resting O2 consumption, measured from 10 until 20 h after feeding, by 12%, but it had no effect on O2 consumption when the intake was 20 g feed/kg. Exposure to mild cold (15°) caused an increase in O2 consumption and this was reduced by 14% after injection of propranolol.

The stability of potassium tetrathiomolybdate was studied in vitro using solutions with molybdenum, hydrogen ion and phosphate concentrations similar to those normally found in the rumen. Under these conditions K2[MoS4] hydrolysed rapidly and as a result the solution contained [MoS4]2−, [MoOS3]2−, [MoO2S2]2−, [HS]− and H2S in equilibrium. In view of this hydrolysis, in vivo studies of thiomolybdate on copper metabolism of sheep should not exclude the possibility that either sulphide or molybdate is responsible for any observed effect.