1. A study was made of the partition of the major constituents of rat's milk during the formation of the clot in the infant rat's stomach.

2. Milk was obtained from the dams by manual expression after separation from their litters for periods ranging from 12 to 23 h.

3. The ratio of fat to protein in the clots removed from the stomachs of the 11-day-old pups was more than double that found in the milk. The difference was due to the high fat content of the clot.

4. The stomach contents of DUDS which were allowed to suckle for I h following a 12 h separation from their dams had fat to protein ratio similar to that of the expressed milk, When suckling was prolonged, the ratio reverted to that of the established clot.

5. Milk secreted under conditions of uninterrupted lactation and promptly recovered from the stomachs of pups previously fasted had a value for fat to protein comparable to that for the clot from a normally fed pup. An interruption in suckling therefore reduced the fat content of the milk.

6. Part of the carbohydrate in rat's milk is secreted in a bound form. Lactose accounts for approximately one half of the total carbohydrate. Evidence is presented which suggests that the remainder may be an isomer of lactose.

7. Fat and lactose undergo hydrolysis to a small extent only in the pup's stomach. The breakdown of protein is insignificant. Rat's milk contains no proteolytic enzymes.

8. No significant differences in composition were found in the outer shell, the core and pyloric regions of the clot. Thus fat and casein leave the stomach in constant proportion.

1. In four feeding experiments with sheep the utilization of proteins contained in lucerne hay and of those in toasted soya-bean meal (SBM), representing a roughage and concentrate feed respectively, were examined. The ration of one group of animals contained lucerne hay as sole source of digestible protein and that of the other SBM.

2. Measurements of the nitrogen balance showed clearly the superiority of lucerne hay as protein source compared with soya-bean meal; this arose from the greater N retention found with the lucerne hay ration.

3. The influence of both rations on the metabolic pathways of the proteins was examined by following the changes of concentration of various metabolites in the rumen contents and of blood urea at different intervals after feeding.

4. Concentrations of urea found in the blood of the sheep given lucerne hay were lower than those of the other group, a finding which is in agreement with the results of the balance experiments.

5. The concentrations of NH2-N and of aminoacids in the rumen liquor were higher in sheep given lucerne hay than in those given SBM. These concentrations appeared to be related to the differences between the soluble non-protein N contents of the two feeds.

6. The results agree with the finding from in vitro experiments that rumen liquor from sheep receiving lucerne hay promoted greater synthesis of protein than rumen liquor from sheep receiving SBM.

7. Total bacterial activity as measured by the reduction of triphenyltetrazolium chloride (dehydrogenase activity) was much higher in the rumen liquor of sheep given lucerne hay than when SBM was given.

8. The concentrations of volatile fatty acids (C2-C6) were much higher in the rumen liquor in sheep on the lucerne hay diet than in those on the SBM diet. After meals of the lucerne hay diet, the concentrations of acids higher than C2, particularly those of valeric acid, exceeded those present in the rumen liquor of the animals kept on the SBM diet.

9. Proline and alanine appeared in relatively higher concentrations in the rumen liquor than the other amino acids determined, and these two acids together with valine disappeared very rapidly. The possible conversion of these amino acids into valeric acid is considered. It is suggested that valeric acid found in relatively high concentrations in rumen liquor of sheep given lucerne hay may be due in part to the deamination of proline, which likewise disappeared very rapidly together with alanine and valine.

1. Eight groups of ten weanling rats were maintained for 60 days on diets containing calcium and phosphorus in the ratio 10:1 at four different levels of mineral, namely 0.8, 1.19, 2.29 and 3.33% Ca.

2. At the two lower levels of mineral intake the provision of vitamin D reduced final body-weight. Increasing the mineral intake increased final body-weight except at the highest level.

3. Increasing the dietary mineral content had no effect on serum Ca, but serum P was higher in the groups receiving the two higher levels of dietary mineral. Vitamin D raised the serum Ca level in the rats receiving the two lower levels of mineral, and serum P was raised by the vitamin at all levels of mineral intake.

4. Provision of vitamin D at the two lower levels of mineral intake decreased the fresh weight, dry weight and volume of the humerus but had no significant effect on the absolute amount of mineral ash in the bone. Consequentially there was an increase in percentage of ash, overall density and the ratio of weight of ash to organic matter in dry fat-free bone (A:R value). With increasing mineral intake there was an increase in all the bone measurements except volume.

5. The presence of vitamin D had no effect on tooth mass or ash content. Increasing the mineral intake caused an increase in tooth mass and ash except at the highest level of intake.

6. The ratio of tooth ash to bone ash was very much greater at the lower levels of mineral intake than at the higher levels.

7. In the animals on the two lower levels of mineral intake the bones were frankly rachitic, and the presence of vitamin D ameliorated the condition. With increase in mineral intake histological signs of rickets were reduced, but even at the highest level of dietary mineral the epiphyseal discs appeared slightly wider than normal.

8. The incisor teeth of animals on the two lower levels of dietary mineral had wide predentine, and the presence of vitamin D reduced the amount of predentine. At the two higher levels of mineral intake the dentine appeared normal when vitamin D was present in the diet.

9. Quantitatively, the bones were much more affected than the teeth by a low intake of mineral at a Ca to P ratio of 10:1.

1. Adult rats were maintained on a protein-deficient diet for 6 weeks following which laparotomy was performed and peritoneal wounds of standard size were constructed,

2. The diet resulted in a progressive weight loss and a fall in plasma protein. Tissue protein, expressed as percentage protein in dried voluntary muscle, did not fall significantly.

3. Following laparotomy the rats were killed in groups on successive days and the peritoneal wounds were removed for measurement of area and for histological examination.

4. There was no apparent difference between control and protein-deficient animals in the rate or extent of peritoneal wound contraction although there was histological evidence of delay of collagen formation in the protein-deficient animals. This supports the theory that collagen formation is not a function of wound contraction.

1. Four wether sheep, each fitted with re-entrant duodenal cannulas and a rumen cannula, were used to determine the relative quantitative importance of digestion in the stomach compared with that in the intestines when diets of low (HM1) and high starch (CM1) content were fed at 0.9 times maintenance and when the high-starch diet was fed at 1.7 (CM2) and 2.3 (CM3) times maintenance. Paper, impregnated with chromic oxide, and polyethylene glycol (PEG) were administered.

2. An apparatus is described which allowed one operator to collect, record, sample and return the duodenal digesta from two sheep simultaneously.

3. Total digestion was determined by faeces collections over 7–10 day periods, and digestion in the stomach by measuring the total flow of digesta from the abomasum to the duodenum over two 24 h periods with two or three sheep on each ration. Flow values were adjusted to give 100% recovery of chromic oxide.

4. The recoveries of chromic oxide and PEG were similar and it was concluded that either marker was satisfactory for adjusting 24 h flow values. Disadvantages of using PEG are discussed.

5. There was relatively little difference between rations HM1 and CM1 in the proportion of digestible organic matter and energy digested in the stomach. Only 57.1% of the total dry-matter digestion occurred in the stomach for ration HM1 compared with 65.0% for ration CM1 reflecting a smaller net gain in ash for ration CM1. Doubling the level of intake (ration CM2) resulted in a decrease in the proportion of digestible dry matter, organic matter and energy digested in the stomach. When the level was increased still further with ration CM3, the proportion continued to decrease with one sheep but increased with the other.

6. All but 5–11% of the digestible starch (measured as α-linked glucose polymer) was fermented in the stomach, the lowest proportion being with ration HM1.

7. The amount of nitrogen reaching the duodenum was approximately equal to the amount ingested with rations HM1 and CM1 but considerably greater with the other two rations. All rations contained approximately 2% nitrogen.

8. Calculation of the estimated loss of energy as methane and heat of fermentation suggested that 50–54% of the digestible energy was absorbed as volatile fatty acids.

1. It was shown that when polyethylene glycol (PEG) was added to suspensions of food particles in aqueous buffer solutions, its distribution in the total water of the food mass was not uniform. The marker was excluded from a large proportion of the water contained in the swollen food particles. This effect was independent of temperature, pH, and, within limits, the time of contact.

2. It was shown that the theoretical concentration (C0), assuming a uniform distribution of marker, could be calculated from the observed concentration (C), weight of food in suspension (W) and the total volume of water (V), using the equation C = C0(I + b[W/V]) where b is constant for any given food. The addition of PEG solution to dry food particles gave a smaller effect.

3. The distribution of PEG was usually, but not invariably, more uniform in a suspension of roughages than in a suspension of concentrates.

4. Possible implications of these findings with respect to marker experiments with PEG are discussed.

1. The behaviour of fatty acids in dilute bile salt solution and in dispersions of triglyceride in bile salt solution was examined. The properties of fatty acids in bile salt solution were defined in terms of their saturation ratio, and of the critical micellar concentration of bile salt for each fatty acid as solute. The partition of fatty acids between the oil phase and the micellar phase of the dispersions was defined as the distribution coefficient K M/O. The phases were separated by ultracentrifugation.

2. Of the fatty acids examined, palmitic and stearic acids behaved in bile salt solution as typical non-polar solutes. Lauric, oleic and linoleic acids had properties similar to typical amphiphiles. The effectiveness of these and other amphiphiles was expressed in terms of an amphiphilic index.

3. The trans-fatty acids, vaccenic acid and linolelaidic acid possessed solubility properties similar to their cis-isomers. The properties of elaidic acid were intermediate between those of the non-polar and the amphiphilic solutes.

4. The distribution coefficients of fatty acids differed less significantly than their solubilities in bile salt solution, but were influenced to some extent by the composition of the oil phase.

5. The effect of pH on the partition of fatty acids was similar for all fatty acids examined. There was a marked increase in the partition of fatty acids in the micellar phase as pH increased above 6.2.

6. In the presence of Ca2+ ions above a threshold concentration of I m-equiv./l. and at a pH higher than 6.4, the partition of stearic acid in the micellar phase of the bi-phasic system was restricted. No interaction of Ca2+ ion and pH was observed with oleic acid.

7. The effect of some amphiphiles on the distribution coefficient of stearic acid was examined. The capacity of lysolecithin to solubilize stearic acid in the micellar phase of dispersions was about twice that of I-mono-olein. The significance of the results in relation to fat absorption in the pig and the sheep is discussed.

1. Individual energy intakes and expenditures of seven Tristan men aged between 16 and 57 years, and ten Tristan women aged between 15 and 61 years, were measured daily for 7 consecutive days between May and October 1966.

2. Details of the subjects' main activities together with the energy cost of these activities are given.

3. The mean daily calorie intakes were 2650 kcal for men and 1830 kcal for women; the mean expenditures were 2860 and 2060 kcal per day respectively. Separate values are given for two individuals, a brother and sister, who gave results bearing no resemblance to those of the rest of the subjects.

4. Protein, fat, carbohydrate and alcohol accounted for 12.7, 29.6, 53.7 and 40 % respectively of the men's total calorie intake and 11.9, 27.2, 61.0% and 0% of the women's total calorie intake. The fat content of the diet was low when compared with that of the Islanders' diet while in England, though total calorie intake was greater (Taylor, Hollingsworth & Chambers, 1966). More than half the total calorie intake was provided by processed foodstuffs, but island produce provided a large proportion of the protein in the diet.

5. It is deduced that mean energy requirements of about 2750 kcal per day for men and 1950 kcal per day for women are adequate for the Tristan population and that there are sufficient food supplies available to meet this requirement.

1. Lambs fitted with cannulas in the abomasum, terminal ileum and caecum were used to study the digestion of starch and dry matter when rations with high starch content were given. Polyethylene glycol was used as an indigestible reference substance.

2. In Expt I reduction in level of feeding from an estimated ad lib. intake to 70% of this level reduced the amount of dietary starch escaping fermentation in the rumen from 6.8 to 4.4% of intake on a barley diet and from 12.8 to 7.7% on a diet consisting of 40% dried grass and 60 yo barley. Inclusion of 40% chopped dried grass in the diet increased the amount of dietary starch escaping fermentation in the rumen. There appeared to be a linear relationship between the concentrations of starch in abornasal and ilcal dry matter, indicating a limited capacity for starch digestion in the small intestine.

3. In Expt 2 a barley diet was compared with diets based on flaked maize, ground maize or cracked maize. With these diets the percentage of dietary starch escaping fermentation in the rumen was respectively 6.2, 5.4, 12.1 and 142, showing that more starch escapes fermentation with uncooked maize diets than with barley diets.

4. The molar proportions of volatile fatty acids produced by fermentation in the caecum were apparently influenced by the amount of starch passing to the intestines. The highest proportion of acetic acid (78%) was associated with 4.5% of starch in abomasal dry matter, and the lowest proportion (57%)was associated with 20.1% of starch in abomasal dry matter.

5. The possible relationships between the extent of fermentation in the rumen and energy and nitrogen metabolism are discussed.

1. A vitamin E-low diet containing 7% stripped lard was given to hooded rats for periods up to 14 months. Control rats were given the same diet with a vitamin E supplement (I i.u./rat per day).

2. No consistent pattern of changes was found in the total fatty acids of testis, lung, spleen, pancreas, heart, kidney, liver, brain, skeletal muscle and small intestine from rats given the deficient diet for 5, 6 or 7 months when compared with control rats.

3. The fatty acids of the total phospholipid from the same tissues were examined after 4, 5, 8 or 14 months. In the rats deficient in vitamin E the polyunsaturated fatty acids of the linoleic series (ω6) decreased, except for 20:4ω6, which in some tissues tended to increase. After 14 months there were considerable decreases in the percentages of all the ω6 series including 20:4ω6 with increases in the percentages of 18:1ω9 and 20:3ω9 the pattern was similar to that found in essential fatty acid deficiency.

1. It has been suggested that carbon tetrachloride damages rat liver by accelerating processes of lipid peroxidation at subcellular sites and that the protective action of vitamin E is due to its functioning as an antioxidant in vivo. Direct evidence for these mechanisms in vivo has been sought and is critically examined.

2. The increased production of malondialdehyde by rat liver microsomal fractions during incubation with CCl4 was shown to be a function of the vitamin E status of the rat and of an in vitro reaction, which could not be correlated with the hepatotoxic action of CCI4.

3. Evidence for the production of lipid peroxides by CCl4 in the livers of vitamin E-deficient and vitamin E-supplemented rats was sought (I) by measurement of ultraviolet spectral changes ('diene' formation) and (2) by direct micro-iodimetric determination of the peroxide. No differences in peroxide content were found between CC14-treated and control rats, nor were the spectrophotometric changes in the ultraviolet region related to the presence of vitamin E.

4. The effect of CCI4 (2.0 ml/kg orally) on ATP levels in rat liver was studied at intervals from 3 to 68 h. The primary lesion leading to necrosis and fat accumulation after CCl4 treatment occurred many hours before the eventual slight decline in ATP. Although the levels of ATP were somewhat higher in vitamin E-deficient rats, vitamin E did not prevent the slight decline in ATP that took place. Since ATP is known to be highly sensitive to peroxidation, the results suggest that lipid peroxidation is not the primary event in CCl4 poisoning.

5. The effect of CC14on the metabolism of [14C]D-α-tocopherol in the rat was studied. A single intraperitoneal dose of CCl4 (2.0 m/kg) did not increase the destruction of α-tocopherol in the liver or carcass after 24 h. Three smaller daily doses of CC14 (0.25 ml/kg) also did not increase α-tocopherol catabolism; on the contrary, significantly more α-tocopherol was found in the livers of rats treated with CCI4. These results suggest that CCl4 does not increase lipid peroxidation in vivo.

1. Individual body fat and body measurements such as lengths, girths and selected skinfold thicknesses were determined in our laboratory strain (BHE), a highly inbred strain (IN) of BHE rats and in a strain of Wistar rats. Measurements were made on unconscious rats in less than 5 min per rat just before autopsy; body fat content was determined in individual rats of both sexes at 50, 100 and 300 days of age.

2. Among the strains, mean total body fat was highest in BHE rats at each age; IN rats of similar average body size were leanest. Statistically significant differences in body fat among the strains were due primarily to differences among the male rats at 300 days. Total protein and skeletal mass increased with increases in age and body size, as did body fat in rats after maturity. IN rats had the largest fat-free weights. Although significant age differences in body fat and body measurements occurred, they were in part dependent upon changes in body- weight, sex and strain of the animals. Female rats had more fat per unit body-weight than males at each age studied. Females, though fatter than males, had smaller skinfold thicknesses, indi- cating that female fat increases are primarily in visceral fat.

3. Large variation in fat among individuals within strains of the same body-weight and age suggests a genetic influence in fat potential in rats not associated with age or body-weight.

4. Results from multiple regression analyses showed differences among adjusted means and partial regression coefficients due to strain and sex of the animals. Although final body-weight was the predictor common to all equations, body length, abdominal girth and subscapular skinfold were common to all but one set of equations. Chest girth, tibia length, triceps and abdominal skinfolds decreased in frequency of appearance in that order. Some of the measurements were more effective predictors at one age than at another. It was clearly necessary to take into account body dimensions other than weight to obtain an optimal prediction of body fat.

5. Differences in characteristics of the rats support the concept of genetic influences in fat deposition in individuals and indicate the complex nature of these influences.

1. Samples of subcutaneous (inguinal) and perinephric adipose tissue were obtained, at slaughter, from each of twenty male calves. Three were neonatal animals, three were 3 days old and two were fed on reconstituted milk to appetite until they weighed 100 kg. The other twelve calves were given milk until they reached 50 kg live weight; concentrates were then included in the diet until, at 60 kg live weight, six calves were slaughtered. The remaining six calves were raised to 100 kg on concentrates alone. The weight of the empty reticulo-rumen of each slaughtered calf was recorded.

2. The component fatty acids of the adipose tissue triglycerides of the neonatal and 3-day-old calves were very similar; about 80% consisted of oleic acid (18:1) and palmitic acid (16:0) and the remainder comprised stearic acid (18:0), palmitoleic acid (16:1) and myristic acid (14:0), together with very small amounts of other acids which, in the glycerides of the 3-day-old calves, included some evidently of colostral origin. The perinephric glycerides of both these groups of calves were somewhat more unsaturated than were those of subcutaneous adipose tissue.

3. The continued consumption of milk by the calves slaughtered at 60 kg live weight was reflected in the presence of enhanced proportions of 14:0, 18:2, 17:0 and 17:1 in the depot triglycerides and, in addition, very small amounts of branched-chain acids and trans 18:1 were detected. A similar fatty acid pattern was observed in the triglycerides of the calves which were given milk only until they were 100 kg live weight. In all these calves only limited growth of the rumen took place.

4. By contrast, the calves which were raised on solid feed from 60 kg to 100 kg and in which rumen development had taken place had depot triglycerides whose fatty acid composition resembled that found in adult animals. Increased proportions of stearic acid accompanied by relatively large amounts of trans 18:1 were present, evidently as a result of the assimilation of the products of bacterial modification of dietary fatty acids in the rumen.

5. Regardless of the age of the calves and the over-all fatty acid composition of their tissue triglycerides, the intramolecular disposition of the fatty acids was similar in that saturated components were present esterified mainly in positions 1 and 3, and unsaturated acids for the most part in position 2; the only major exception to this distribution pattern was in respect of trans 18:1 which, when present, was preferentially esterified to the primary alcoholic groups of the glycerol moiety as if it were a saturated acid.

1. A semi-synthetic vitamin B12-deficient diet, based on soya flour, is described. When supplemented with cydnocobalamin the diet appeared to be adequate for growth and reproduction in the rat.

2. Compared with their litter-mates on the supplemented diet, rats fed on the deficient diet from weaning showed reduced levels of vitamin B12 activity in the plasma and tissues, but their growth rates were unaffected unless they were bred from mothers that had been given the deficient diet since mating.

3. When they were reared on the deficient diet, rats bred from mothers on the deficient diet since mating excreted much more methylmalonic acid in the urine than their litter-mates on the supplemented diet. There was wide variation in the level of excretion, both between different animals and from day to day in the same animal.

4. Starvation for more than 16 h caused a marked depression in the amount of methylmalonic acid excreted by rats on the deficient diet.

5. Intraperitoneal injection of sodium propionate into deficient animals after starvation for 24 h caused increased excretion of methylmalonic acid during the following 16 h of continued starvation. Isoleucine had a similar but smaller effect.

6. Tested in the starved animal, sodium propionate and valine given either by intra- peritoneal injection or by mouth, and isoleucine given intraperitoneally, caused increases in the excretion of methylmalonic acid. In contrast, methionine had no effect and threonine only a slight effect.

1. In seven experiments sheep were given diets ranging from all-hay to all-barley, and also a diet comprising one part hay to two parts flaked maize. Each sheep was equipped with a cannula into the rumen and a re-entrant cannula in the proximal duodenum; six of the ten also had a re-entrant cannula in the terminal ileum. Paper impregnated with chromic oxide (Cr2O3) was given twice daily by rumen fistula.

2. Amounts of α-linked glucose polymer entering and leaving the small intestine and excreted in the faeces were measured. Some values for a fraction designated non-glucose reducing polymer for cellulose and for gross energy were also obtained. The amounts passing the proximal duodenum and the terminal ileum were adjusted to give 100% recovery of Cr2O3 and the values were used to measure the extent of digestion in various parts of the alimentary tract.

3. When rolled or whole barley was given alone or was the major feed constituent the amount of α-linked glucose polymer entering the small intestine was 6.0±0.76% of that ingested (range 2.6–8.1%). The value was significantly lower than that found for the diet of hay and flaked maize (10.4±1.3%, range 8.0–13.6 %).The α-linked glucose polymer which entered the small intestine was almost completely digested there.

4. The digestibility of the non-glucose reducing polymer, which included much of the hemicelluloses present, ranged from 51 to 73% and almost all the digestible fraction (93–97%) was digested before the small intestine when hay or predominantly hay diets were given. On high-cereal diets only 71–85% of the digested fraction disappeared before the small intestine and appreciable amounts were digested in the large intestine.

5. On the all-hay diet 91% of the digestible cellulose and 67% of the digestible energy were lost before the small intestine, 0 and 21% in the small intestine and 9 and 12% in the large intestine.

6. Mean digestibility coefficients determined in sheep fed solely on either whole or rolled barley were: for dry matter 88.1 and 87.9%, for nitrogen 83.5 and 82.1%, for crude fibre 53.7 and 56.6% and for gross energy 87.7 and 88.0%.

1. Control groups of pigs were given a basal diet alone and treated groups received the same diet supplemented with 250 ppm of copper. The animals were about 10 weeks of age at the start of the experiments and were killed when they weighed 90 kg live weight.

2. The ratio of oleic acid to stearic acid in the whole back fat (inner plus outer layers) was somewhat higher in the pigs given the copper supplement than in the control animals. The melting point of the back fat was about 10° lower in the pigs given the copper supplement than in the control groups.

3. Separate analyses of the inner and outer layers of the back fat showed that the ratio of oleic acid to stearic acid in the outer fat layer of the control pigs, and in both the inner and the outer fat layers of the pigs given the copper supplement, was somewhat higher than that in the inner fat layer of the control animals. The melting point of the outer fat layer of the control pigs and of both back fat layers in the pigs given the copper supplement was 10–15° lower than that of the inner fat layer of the control groups.

4. Evidence is presented that changes in the positional distribution of the fatty acids within the triglycerides of the back fats rather than differences in gross fatty acid composition are mainly responsible for the observed differences in physical properties.

1. Changes in blood sugar levels after giving carbohydrates have been used to assess carbohydrate utilization in pre-ruminant calves aged between 10 and 50 days.

2. Glucose, galactose and lactose were readily utilized by all calves; the utilization of glucose and galactose increased with age, whereas that of lactose remained constant.

3. Maltose and fructose utilization was low in young calves and increased slightly with age.

4. Sucrose and starch were not utilized.

5. Studies with three older pre-ruminant calves (aged 53, 88 and 106 days) in which the carbohydrates were infused into the proximal duodenum showed that glucose, galactose, lactose and xylose all caused marked increases in the level of blood reducing sugar, whereas fructose and sucrose caused no increase, and maltose was intermediate. Xylose and galactose caused very little change in the blood glucose concentration.

6. It appeared that preferential uptake occurred of glucose from a glucose-galactose mixture.

7. A non-linear relationship was found between the concentration of glucose or galactose infused and the increase in the level of blood reducing sugar.

1. Fluids were given by mouth in various ways to young sheep. The extent to which closure of the oesophageal groove operated to direct the fluid to the abomasum was assessed by radiography.

2. Salt solutions and milk given as a drench did not produce complete closure of the groove. However, when the animals were accustomed to sucking from a teat before weaning, any liquid suspension and also water, sucked from a bottle, passed entirely to the abomasum even in 12-month-old sheep.

3. This technique may be useful when it is desirable to cause protein or other nutrients to by-pass fermentation in the rumen.