1. In one experiment the effect on rumen pH of feeding with restricted amounts of whole or pelleted barley was studied. With whole barley there was little variation in rumen pH associated with feeding time, but with pelleted barley the pH decreased from about 7.0 before feeding to about 5.3, 2–3 h after feeding.

2. The rate of disappearance of dried grass during incubation in the rumens of sheep receiving either whole or pelleted barley was studied in a second experiment. After 24 h incubation only 423 mg/g incubated had disappeared in the rumen of sheep receiving pelleted barley while 625 mg/g incubated had disappeared when it was incubated in the rumen of sheep receiving whole barley.

3. The voluntary intake of dried grass by lambs was studied in a third experiment when they received supplements of either 25 or 50 g whole or pelleted barley/kg live weight0.75. At the high level, pelleted barley reduced intake of dried grass by 534 g/kg but whole barley reduced it by only 352 g/kg. The digestibility of acid-detergent fibre was reduced more by pelleted barley than by whole barley but there was a tendency for a small increase in digestibility of the barley due to processing.

4. The implications of these findings on supplementation of roughages with cereals are discussed.

1. Measurements were made of portal blood flow, heat production and oxygen consumption in the digestive tract of sheep either fasted or given the following diets: chopped, dried grass; pelleted, dried grass; chopped, dried lucerne; pelleted, dried lucerne; or a pelleted baley diet.

2. For sheep that had been fasted for 48 h, portal blood flow was 1.84 1/min, total visceral heat production was 62.3 kJ/kg body-weight0.75 per 24 h and aerobic heat production, estimated from oxygen consumption, was 62.1 kJ/kg body-weight0.75 per 24 h.

3. Portal blood flow was markedly influenced by food intake, increasing from 1.8 1/min for starved sheep to 2.4 and 4 1/min for sheep fed at maintenance and 2.5 × maintenance levels of intake respectively. Variations in the quality and physical form of the diets had no apparent effect on portal blood flow.

4. There was a curvilinear relationship between total heat production in the gut and metabolizable energy (ME) intake. The increase obtained for levels of intake below maintenance was greatest with lucerne diets, and least with pelleted, dried grass or pelleted barley diets. Above maintenance levels of intake the rate of increase in heat production, with all diets, was about 150 kJ/MJ ME intake.

5. The heat of fermentation, estimated from the difference between total visceral metabolism and the aerobic metabolism of the tissues of the gut wall, was 76, 60 and 22 kJ/MJ digestible energy intake for the dried grass, lucerne and barley diets respectively.

6. The contribution of fermentation heat and the aerobic metabolism of the gut to the total heat increment of feeding in sheep was assessed. It was concluded that about half the heat increment must be derived from tissues outside the digestive tract.

1. The feasibility of improving iron nutrition by fortifying cane sugar with Fe and ascorbic acid was studied.

2. It was found to be possible to add a number of Fe salts together with ascorbic acid to sugar without affecting its appearance or storage properties.

3. The absorption of Fe from fortified sugar eaten with maize-meal porridge or made into jam or biscuits was measured in ninety-four volunteer multiparous Indian women using the 59Fe erythrocyte utilization method.

4. The absorption of Fe from sugar fortified with ascorbic acid and ferrous sulphate and eaten with maize-meal porridge was increased about twofold if the ratio, ascorbic acid: Fe was 10:1 by weight. If the ratio was increased to 20:1, Fe absorption was increased a further threefold.

5. Sugar fortified with soluble Fe salts, including FeSO4. 7H2O, discoloured both tea and coffee; sugar fortified with ferric orthophosphate did not have this effect.

6. Fe from FePO4. H2O was poorly absorbed when added with sugar to maize-meal porridge, and also when added with adequate quantities of ascorbic acid. This form of Fe was absorbed much less well than was the intrinsic Fe present in the maize.

7. When sugar fortified with FePO4.H2O and ascorbic acid was added to maize-meal porridge before cooking or was made into jam there was a several-fold increase in the amount of Fe absorbed.

1. The long-term fate in rats of an oral dose of [75Se]selenocystine was compared with that of an oral dose of [75Se]selenomethionine.

2. Urinary and faecal radioactivities were measured during the 1st week and whole-body radioactivity was determined for 10 weeks. Rats were killed at weekly intervals for 4 weeks and at weeks 6 and 10 for analysis of tissue distribution of 75Se.

3. Intestinal absorption of [75Se]selenocystine was 81% of the administered dose; that of [75Se]selenomethionine was 86%. Urinary excretion of absorbed [75Se]selenocystine was 13.9% and that of [75Se]selenomethionine was 5.8%, in the 1st week.

4. Whole-body retention of 75Se was greater for [75Se]selenomethionine than for [75Se]-selenocystine but after the 1st week it decreased at a similar rate in both groups. Tissue distribution of retained 75Se was also similar in both groups.

5. The initial utilization of [75Se]selenocystine was different from that of [75Se]selenomethionine. However, after the 1st week 75Se from both sources appeared to be metabolized similarly, suggesting that dietary Se of both forms is ultimately incorporated into the same metabolic pool.

6. When these findings were compared with those of earlier studies with [75Se]selenite and 75Se incorporated in vivo into rabbit kidney (RK-75Se) (Thomson, Stewart & Robinson, 1975) the metabolism of [75Se]selenocystine resembled that of [75Se]selenite and RK-75Se, rather than that of [75Se]selenomethionine.

1. A combination of a mineral balance and a radioactive technique has been used to study the effects of increased levels of dietary calcium and phosphorus on the Ca and P metabolism of young and mature wether sheep previously made Ca-deficient.

2. Ca absorption was directly related to Ca intake until an absorption maximum was reached. Young animals absorbed dietary Ca more efficiently than mature animals and had a much higher maximum rate of absorption. Apparent P absorption was directly related to P intake and maximum P absorption was also higher for the young animals.

3. Excretion of Ca in the urine and into the intestine was not altered by changes in Ca intake. Excretion of P in the urine, however, varied considerably and it is suggested that this process may be largely responsible for P homoeostasis.

4. Ca retention was directly related to Ca absorption. Maximum retention was considerably higher for the young animals than for the mature animals and occurred for each group of animals at exactly the same dietary intake as maximum Ca absorption.

5. Ca and P were retained in a constant ratio of 1.25:1 and the results suggested that P retention was controlled by the rate of Ca retention.

6. Bone turnover was higher for the young than for the mature animals. Animals mobilized skeletal Ca when receiving the Ca-deficient diet and replaced their Ca losses when the dietary Ca was plentiful by changing the relative rates of bone resorption and bone accretion. Although bone resorption was mainly responsible for Ca homoeostasis, bone accretion appeared to play some part in the young animals.

7. Maximum retention of Ca occurred just as the rate of bone resorption become zero and was equal to the rate of bone accretion. The lower maximum retention of Ca for mature animals was due to a lower rate of bone accretion.

8. Results suggested that when bone resorption ceased, Ca absorption was regulated by homoeostatic mechanisms at a level just sufficient to maintain maximum retention, and that the maximum rates of absorption measured may not have been true maximum rates.

9. The consequences of a relationship between bone accretion and maximum Ca retention are discussed with reference to older, pregnant and lactating animals.

1. The preparation of a propionylated protein is described, and the effects of this treatment on amino acid composition and availability are compared with the effects of severe heat treatment (autoclaving) of a protein.

2. Using chemical analyses, changes exceeding 5% for total tyrosine, histidine, methionine and cystine contents were found after propionylation of the protein. Autoclaving of the protein resulted in changes in total serine, lysine, methionine, cystine and tryptophan contents.

3. Microbiological estimates of total amino acid contents were not in close agreement with the chemical estimates for the autoclaved protein.

4. Fluorodinitrobenzene-reactive lysine content was reduced to almost zero by propionylation, and by almost 40% by autoclaving.

5. Both propionylating and autoclaving protein reduced the amount of lysine available to the chick by about half. In contrast, the availabilities of methionine and tryptophan to the chick were unchanged by propionylation, but were reduced to 0.66 and 0.44 respectively, relative to the untreated protein, by autoclaving.

6. Because of the difficulties of obtaining reliable absolute estimates of amino acid availability using chick growth assays, our interpretation of results is mainly based on relative values. The merits of microbiological microbiological estimates of amino acid availability are assessed.

1. Twenty-two samples of high-protein feeding-stuffs, sixteen of them fish meals, were used in a collaborative study of the precision and the limits of discrimination of the Streptococcus zymogenes assay procedure, as applied to the estimation of available methionine, tryptophan and isoleucine contents.

2. All the participating laboratories ranked the test samples in much the same sequence with respect to content for all three amino acids. There were apparently systematic differences between laboratories which impaired the precision of some of the estimates, and these were greatly reduced by including a common reference sample in the tests as an auxiliary standard.

3. Values for available methionine content for eleven test samples were highly correlated (r 0.86) and quantitatively similar to those obtained for chick growth assays, but those for available tryptophan content were markedly lower and were probably in error.

1. Rats were undernourished in early life by feeding their mothers a restricted quantity of a good-quality diet during pregnancy and lactation. All offspring were fed ad lib. from weaning. Behavioural tests were done using adult males.

2. Thresholds of aversion to electric shock were determined in a rectangular box, one side of which was designated ‘live’ and the other ‘safe’ (o V side) for any particular shock level. Three 15 min sessions were given at each of five shock levels. Previously undernourished rats had a lower aversion threshold than controls. They spent more time than controls on the o V side at two intermediate levels of shock.

3. Other male rats were subjected to six graded series of brief, unavoidable shocks. Previously undernourished rats responded to a greater total number of shocks than controls.

4. These results support the hypothesis that previously undernourished rats have a lowered threshold of arousal.

1. Dietary histories covering I week were obtained from 212 men and 263 women, aged 62–90 years, who formed a random sample of the older people living in a defined area of Edinburgh. The histories were validated by 2 d weighed-diet records for 219 of the subjects.

2. Nutrient intakes are given as mean values and standard deviations, and as percentage distributions of intake relative to the recommended intakes of nutrients. Intakes are also related to factors which might affect diet adversely.

3. Mean values obtained suggested that intakes were less than recommended intakes for more nutrients for women than for men, particularly values for energy and vitamin D. Values for percentage distributions indicated that a substantial proportion of all subjects had low intakes of ascorbic acid and vitamin D, that the energy intake of many women was low and that for most nutrients a greater proportion of men than of women had the recommended intake. Factors associated with significant proportions of subjects with less than the recommended intakes were mental illness in women and deafness and severe dyspnoea in men.

4. Possible action to improve the diet of the elderly is discussed.

1. The digestibilities of protein and amino acids have been estimated by two different techniques: the analysis of faeces (conventional method) and the analysis of ileal contents (ileal technique).

2. Freeze-dried muscle protein was found by both techniques to be almost completely digested. After autoclaving, the digestibility for the same protein was estimated by the conventional and ileal techniques to be 0.65 and 0.57 repectively.

3. Unmodified lactalbumin was found by both techniques to have a digestibility of about 0.90. Propionylation of the lactalbumin reduced digestibility to 0.82 and 0.79 as indicated by faecal analysis and ileal content analysis respectively.

4. In general, the digestibilities of individual amino acids in any one protein sample were rather uniform, and reflected over-all protein digestibility. For each amino acid, digestibility, as determined by the both methods, was lower for the modified protein than for the corresponding control protein: estimates based on ileal content analyses were consistently lower than those obtained by conventional analyses. The ileal technique was considered to be both more convenient and meaningful.

5. From the results obtained by the ileal technique it appears that reduced digestibility is an adequate explanation for the reduction found in nutritional value of the autoclaved protein. In contrast, for the propionylated protein, reduced digestibility of lysine is only a partial explanation of the low availability of this amino acid as estimated by chick growth assay.

6. In our experiments we found that the type of dietary protein used did influence the amino acid composition of the ileal contents. This was most marked with the least-digestible protein. These findings do not support the views of Nasset (1962).