1. Six groups of four litter-mate female Large White pigs of about 17 kg live weight were allocated according to a 2×2 factorial design in each of two experiments in which rations containing 0 or 750 ppm copper were offered with either 0 and 500 ppm zinc, or 0 and 750 ppm iron. 2. Severity of toxicosis was assessed by determining aspartate transaminase activity in serum, observing the incidence of jaundice and determining the hemoglobin concentration in whole blood and Cu concentration in serum and liver. 3. Addition of 750 ppm Cu to the diet caused toxicity in nine out of twelve animals; it was most severe after about 4 weeks when two-to five-fold increases in serum Cu and aspartate transaminase levels were found and seven pigs were jaundiced. Serum Cu and aspartate transaminase concentrations and degrees of jaundice were apparently interrelated and returned to normal levels after 6 weeks, suggesting adaptation to the high Cu intake. Growth depression and a microcytic hypochromic anaemia persisted. 4. Addition of 500 ppm Zn or 750 ppm Fe in the presence of 750 ppm Cu eliminated jaundice and produced serum Cu and aspartate transaminase concentrations similar to control values after 4 weeks. Only supplementary Fe afforded protection against anaemia. 5. Variability in the response of the pig to Cu supplements could be partly due to variations in the intake of Fe and Zn. The addition of Fe and Zn supplements to pig diets supplemented with Cu would probably reduce the small risk of causing Cu poisoning.

1. The diets of sledge dogs at a British Antarctic sledging base were studied both at base and during sledge journeys, and samples of the diets and the relevant faeces were analysed. Changes in weight were related to calorie intakes.

2. The calorific requirements of sledge dogs were found to vary considerably from dog to dog and depended on the activity in which the dogs were involved. Whereas 2500 kcal/dog daily were just sufficient to maintain the body-weight of a completely idle dog, 5000 kcal/dog were insufficient to maintain the body-weight of a dog pulling a heavy sledge over long distances.

3. Seal meat was found to be the most beneficial and most satisfactorily absorbed diet. The artificial diets, pemmican and Nutrican, were adequate to maintain body-weight if sufficient supplies were available to give dogs as much as twice the routine ration, but were uneconomical in that large quantities of nutrients were passed in the faeces.

1. Six groups of three (Expt 1) or four (Expt 2) female litter-mate Large White pigs were allocated after weaning to three or four treatments in a randomized block design. 2. In Expt 1, 600ppm copper were added to diets based on maize meal and containing either soya-bean meal, dried skim milk or white-fish meal to provide 16% total crude protein. Severity of Cu toxicosis was assessed by estimating aspartate transaminase (AST) activity in serum, Cu levels in serum and liver, haemoglobin concentration and the incidence of jaundice. 3. Toxicosis was severe only in pigs receiving white-fish meal, but liver Cu and haemoglobin levels were similar in all groups. 4. In Expt 2, 0, 250 or 425 ppm Cu or 425 ppm Cu+150 ppm zinc+150 ppm iron were added to the maize-white-fish meal diet from which the normal Zn and Fe supplements were omitted, creating optimal conditions for development of Cu toxicosis. 5. In the absence of Zn and Fe supplements, 425 ppm Cu caused the development of a severe toxicosis. Simultaneous addition of Zn and Fe supplements eliminated all signs of toxicosis. 6. Under the same conditions 250 ppm Cu caused a mild toxicosis and also exaggerated the slight signs of parakeratosis or Zn deficiency noted in control animals. 7. High calcium levels of 1.7% in a basal diet containing 30 ppm Zn probably induced a marginal Zn deficiency which favoured the development of Cu toxicosis. Differences in calcium level were probably responsible for the apparent effects of the different protein supplements in Expt 1. 8. Occasional occurrences of toxicity in pigs given 250 ppm Cu as a growth stimulant may be partly due to the use of diets low in Zn and Fe and high in calcium. Correcting these factors would extend the safety of Cu supplementation of the commercial diets.

1. A preliminary study was made of chewing duringeating with a total of sixcows with rumen fistulas, given diets of hay or herbage. A sieving technique was used to determine the size of particles of food swallowed at intervals throughout the eating period. The number of jaw movements, number and weight of the swallowed food boluses and the time spent eating were measured with each diet.

2. The mean particle size of hay contained in a bolus collected at the cardia varied between individual cows from 1602 μm to 1244 μm. Boluses swallowed in the first few minutes of eating contained particles of a larger average size than those at any other time during the meal. Also, the rate of swallowing boluses of food was much faster at the beginning of a meal and the weight of boluses smaller than at any other time. The frequency of jaw movements did not vary appreciably during a meal.

3. Increasing the amount of hay given to the cows by 50 % or giving a different hay did not cause any significarlt alteration in the average size of particles of swallowed hay, and changes in the rate of swallowing boluses, or in, the rate of jaw movements and the size of boluses were not very marked.

4. With a diet of herbage, boluses were swallowed rapidly and the average particle size of swallowed food was larger than that of hay. Also, there were slightly more jaw movements per min and larger boluses than with hay.

5. The observations made in the study are discussed in relation to possible factors that determine the particle size of swallowed food.

1. An assessment of the Islanders' food consumption on Tristan da Cunha before the volcanic eruption of 1961 was made (Part 1). The mean daily intake of energy was 2030 kcal per person and the calories derived from protein, fat, carbohydrate and alcohol accounted for 21, 26, 50 and 3% respectively of the total calorie intake, the proportion of calories derived from protein being about twice that found in other types of diet. 2. The weekly food intake of thirty-seven families resident at Calshot, Hants, was measured in July 1963, 3–4 months before the Islanders left England to return to Tristan da Cunha (Part 2). The mean intake of energy was 1750 kcal per person per day and the calories derived from protein, fat and carbohydrate accounted for about 12, 41 and 47% respectively of total calorie intake, proportions similar to those found in present-day British diets. The proportion of other nutrients in relation to calories also resembled those in British diets, except for vitamin A and ascorbic acid, which were relatively low in the Tristan diet. 3. A comparison of the results for the Islanders with those for a sample of households surveyed for the National Food Survey was made. The Islanders consumed less of all nutrients, and the average energy value met only 65% of estimated requirements compared with 108% in the British sample. 4. Details of foods consumed and of the Islanders' food patterns and preferences are given. There is some evidence that the Tristanidns did not like their former staple foods, potatoes and fish, as available in England, though at the time of the survey they had not appreciably switched to the British staple, bread. 5. The relatively low food intake reported in this study conforms with that recorded in the Norwegian investigation of 1937–8 (Henriksen & Oeding, 1946) and with calculations of island food supplies before 1961 (Part 1). 6. Possible explanations for the low food intake are discussed. It is suggested that the Islanders may not be very active and that energy balance studies on individuals who have returned to Tristan da Cunha might throw some light on the results of this survey.

1. Rats were given a rachitogenic diet with or without vitamin D for 1, 2, 3 or 4 weeks, and vitamin D was administered to a group of rats which had been deprived of vitamin D for 3 weeks. 2. Changes in enzyme activities of some tissues were followed histochemically. In general, changes in parathyroid preceded those in gut and kidney. Leucine aminopeptidase activity rose in the parathyroid, kidney and jejunum of the vitamin D-deficient rat as did the ribonucleic acid content of the parathyroid and the dehydrogenase activity of the gut. In contrast, the phosphatase activity of the gut and kidney fell in the vitamin D-deficient rat. All these changes were reversed during the 1-week recovery period. 3. A slower response of bones to both vitamin D deprivation and vitamin D dosage after deprivation was indicated by the changes in the percentages of ash in the bones and the changes in number and distribution of osteoclasts.

1. The nutrient content and distribution of the carcass meat in broilers (B) and free range cockerels (FR) was studied in two experiments in 1961–2. Half the birds of each type were roasted at 177°C, without additional fat, before dissection and analysis. The breast muscles and red meat were separately analysed for moisture, protein, fat and thiamine. 2. Chunky hybrids (frozen) and Light Sussex × Rhode Island Red (LS × RIR) cockerels were used in both experiments. Expt 1 (group 1) was a pilot study (using groups of six) inwhich B and FR of similar dressed weight were compared. Expt 2 (group 2) consisted of twelve ‘fresh’ (B1) and twelve frozen (B2) broiler hybrids from the same batch of birds killed at 9 weeks; twelve slightly heavier LS × RIR cockerels (FR2) were killed at 18 weeks and twelve Sykes hybrid 3 cockerels (FR1) killed at 20 weeks. The birds received various standard feeds. 3. The edible portion (skin plus meat), expressed as a percentage of the dressed weight, was greater in the free range birds than in the broiler chickens. Increased cooking losses resulting from freezing were responsible for a significantly smaller proportion of edible meat in the cooked frozen broilers. In both groups the edible portion increased with age irrespective of breed or weight. 4. In broiler and free range chickens differenccs in the mean protein content of the total edible meat were small. 5. Fat content appeared to be related to breed as well as to type of bird. In group 1, B contained slightly more fat than FR1. In group 2, B1, and B2, contained significantly more fat then FR1, but the fat content of the raw meat in FR2, was greater. 6. In both experiments the flesh of the free range chickens contained more thiamine than the broiler meat. In group 1 this difference was significant in all the cooked birds; in group 2 significant differences between free range chickens and broilers were found in the breast and red meat of the cooked birds for all comparisons except FR2 and B1. About one-third of the thiamine was lost on cooking both types of chicken in group 1; in group 2 the loss from the broilers was similar but in the FR birds between 18% (FR1) and 26% (FR2) of the thiamine was destroyed. 7. In general the meat of the broilers contained less thiamine and more fat than did that of the free range chickens. Though such differences are of no significance in a mixed diet (as chicken supplies so little thiamine) they are a useful index of differences in nutritive value which result from the different systems of management.

1. Diets containing cottonseed hulls and flaked infrared-toasted soya beans, cottonseed hulls and soya-bean meal or cottonseed hulls alone were fed to three fistulated steers. 2. The diet containing toasted soya-bean flakes was associated with the highest concentrations of total nitrogen, protein N, and ammonia N in the rumen liquor; the diet of cottonseed hulls was associated with the lowest concentrations; and soya-bean meal was associated with intermediate concentrations. 3. Concentrations of residual N were highest in rumen liquor during the first 3 h after feeding when soya-bean meal was given and highest with the other diets between 10 and 12 h after feeding; concentrations of non-protein N were highest with the toasted soya-bean flakes at all times except approximately 2 h after feeding when they were highest with soya-bean meal. 4. The rumen liquor was more acid with soya-bean flakes than with the other diets. 5. The total concentration of volatile fatty acids (m-moles/100 ml) was highest with the diet containing toasted soya-bean flakes, followed by that with soya-bean meal and cottonseed hulls and lowest with the cottonseed-hull diet. The molar percentage of acetic acid was highest with soya-bean meal, whereas its concentration (m-moles/100 ml) was highest with soya-bean flakes. Propionic acid concentrations were highest with the toasted soya-bean flakes. 6. These results indicate that the metabolism in the reticulo- rumen of infrared-toasted whole soya beans given as flakes differs from that of soya-bean meal.

1. Monozygotic twin cattle were used in a preliminary study of the effect of pregnancy and of lactation on the voluntary intake of food and water, and on eating and ruminating behaviour. Also, results are reported of an experiment with five pairs of monozygotic twin heifers to examine the variation within pairs of twins in voluntary intake of food and water and eating and ruminating behaviour.

2. Voluntary food and water intakes were measured during the last few weeks of pregnancy and during early lactation. Within each twin pair one twin was pregnant or lactating and the other non-lactating and not pregnant, and the food and water intakes of a pair of twins were measured simultaneously.

3. On average the variation in voluntary intake of hay within pairs of non-pregnant, monozygotic twin heifers was 0.2 kg or 3 % of the mean daily hay intake.

4. The effect of pregnancy was observed in six pairs of twins and in five of the pairs the pregnant animal ate iess hay than its non-pregnant twinmate; in four of these five pairs the effect was small (13 % ). Changes in eating and ruminating behaviour associated with pregnancy were small; the pregnant animals ate concentrates and hay more slowly and ruminated longer than the non-pregnant animals.

5. Lactation was associated with a mean increase of 29 % in hay intake in eight out of the nine pairs studied. In four pairs of twins given a diet of concentrates alone the lactating animal ate on average 8 % more than the non-lactating animal. The lactating cows tended to eat concentrates and hay more quickly than the non-lactating cows; because of differences in the ratio of hay to concentrates it was not possible to interpret the changes in rumination that occurred with lactation.

1. The effect of dietary protein level and supplementation with thyroxine and thiouracil on depletion of liver stores of vitamin A, on the percentage of liver vitamin A in the alcohol form and on the plasma level of vitamin A and protein has been studied in chicks. In an experiment with cockerels the relation was investigated between the vitamin A level of plasma and the electrophoretic pattern of its proteins.

2. Liver vitamin A depletion was considerably reduced by lowering the dietary protein level.

3. Protein malnutrition lowered the percentage of vitamin A found in the liver in the alcohol form.

4. Depletion of vitamin A from the liver was related to the percentage of vitamin A in the alcohol form.

5. Thyroxine increased both vitamin A depletion from the liver and the percentage of vitamin A in the alcohol form, whereas thiouracil had the opposite effect.

6. Plasma vitamin A, and plasma protein contents were significantly lowered in cockerels receiving a 5% protein diet. The drop in plasma protein level was essentially caused by a reduction of the albumin fraction. No significant change in the levels of globulins was observed even after a 4-week period of protein malnutrition.

7. When the dietary protein level was restored to normal both the albumin and vitamin A levels in plasma increased.

1. Thirty Ayrshire bull calves were used in an experiment to study the effects of diets containing different proportions of concentrates to hay on rumen development at 12 weeks of age. In addition, six milk-fed calves were slaughtered at 3 weeks of age for comparison. 2. Restriction of the maximum daily allowance of concentrates to the lower levels was accompanied by an increase in the voluntary intake of hay, but the performance of calves from 3 to 12 weeks of age was significantly better in calves given the high-concentrate diets. 3. The weight of contents of the reticulo-rumen increased from 0.7 kg at 3 weeks of age in the milk-fed calf to 7.7 kg and 10.9 kg at 12 weeks in calves given the high-concentrate and high-roughage diets respectively. Between 68 and 79% of the total contents of the alimentary tract was contained in the reticulo-rumen of the ruminant calf. The weight of contents of the omasum was significantly greater in calves given 1.36 kg concentrates/day than in those given either 0.45 or 2.27 kg concentrates/day. Equations were developed from the results by which the weight of contents of the various parts of the alimentary tract, and hence empty body weight in the live animal, can be determined from a knowledge of the live weight and daily consumption of concentrates and hay, 4. Volume displacement of the reticulo-rumen tended to increase with increase in the proportion of hay in the diet. The volume displacement of the omasum increased in response to concentrate intake up to a maximum of 1.36 kg/day and thereafter declined, but the nature of the diet had no significant effect on the volume displacement of the abomasum. 5. Calves given the high-concentrate diets had a significantly greater weight of reticulo-rumen tissue at 12 weeks than those given the high-roughage diets. 6. Whereas the thickness of the muscular wall of the rumen did not differ significantly between treatments, there was an increase in the length and density of papillas, particularly in the anterior dorsal and ventral sacs of the rumen, as the intake of concentrates was increased. The results show the marked relationship between the performance of the animal and an advanced stage of development of the rumen papillas.

1. The action of raw and heated soya beans on pancreatic function was studied by measuring the amylase activity of the pancreases and intestinal contents of intact chickens and of chickens with ileostomies at fasting and after eating, before and after adaptation to heated and raw soya-bean diets, with a methionine supplement and without. 2. The concentration of amylase in the pancreases of 8-week-old chickens eating raw soya-bean diets was lower than that of those eating heated soya-bean diets. These chickens were deficient in methionine; supplementation of the raw soya-bean diet with methionine greatly increased the levels of amylase in the pancreases of such chickens; supplementation of the heated soya-bean diet with methionine increased the levels of amylase in pancreases to a smaller extent. 3. Methionine was less effective in increasing the amylase levels of the pancreases of 11-week-old chickens eating raw soya-bean diets, since at this age the deficiency of methionine was much less pronounced. 4. More amylase activity was found in intestinal contents of chickens eating raw soya-bean diets than in those eating heated soya-bean diets. 5. In vitro studies showed that fractions prepared from raw soya beans, all containing high levels of trypsin inhibitors, stabilized amylase activity despite the active proteolysis of other protein substrates in the same amylase-containing mixtures. 6. CaCl2 stabilized amylase activity in vitro in unactivated and activated pancreatic juice as such, and after additions of raw soya beans or their fractions before and after autoclaving. 7. The increased levels of amylase found in the intestinal contents of the chickens eating raw soya beans may represent greater secretion of amylase activity by the pancreas, stabilization of amylase activity by the raw soya bean, or both factors. Interpretation of measurements of amylase activity in the intestinal contents of chickens eating heated or raw soya beans is uncertain. 8. The bearing of this work on current views of the nutritional value of raw and heated soya beans is discussed.

1. A gas-liquid chromatographic method for the detection of phytosterols in tissues and excreta of birds was developed. The limitations of this method are discussed. 2. β- and γ-Sitosterol werc detected in the plasma of adult cockerels and in the plasma, intestinal wall, and liver of 4-week-old cockerels. The proportion of sitosterols in the total sterol absorbed appeared to be affected by the nature of the dietary fat. 3. γ-Sitosterol was more effectively absorbed than β-sitosterol. The ratio of β to γ was altered by the nature of the dietary fat. 4. Using a diet containing 10% triolein and 1% cholic acid, and increasing the dietary plant sterol level up to 2%, increased the proportion of sitosterols in the intestinal wall of 4-week-old cocks. Further increases in dietary plant sterols did not produce additional increases in the proportion of sitosterols among intestinal wall sterols. 5. γ-Sitosterol and traces of β-sitosterol were found in eggs from hens given a diet supplemented with maize stcrols.