Showing papers in "British Journal of Nutrition in 1972"

Dynamic aspects of ammonia and urea metabolism in sheep

Abstract: 1. To obtain a quantitative model for nitrogen pathways in sheep, a study of ammonia and urea metabolism was made by using isotope dilution techniques with [15N]ammonium sulphate and [15N]urea and [14C]urea.2. Single injection and continuous infusion techniques of isotope dilution were used for measuring ammonia and urea entry rates.3. Sheep were given 33 g of chaffed lucerne hay every hour; the mean dietary N intake was 23.4 g/d.4. It was estimated that 59% of the dietary N was digested in the reticulo-rumen; 29% of the digested N was utilized as amino acids by the micro-organisms, and 71% was degraded to ammonia.5. Of the 14.2 g N/d entering the ruminal ammonia pool, 9.9 g N/d left and did not return to the pool, the difference of 4.3 g N/d represented recycling, largely within the rumen itself (through the pathways: ruminal ammonia → microbial protein → amino acids → ammonia).6. Urea was synthesized in the body at a rate of 18.4 g N/d from 2.0 g N/d of ammonia absorbed through the rumen wall and 16.4 g N/d apparently arising from deamination of amino acids and ammonia absorbed from the lower digestive tract.7. In the 24 h after intraruminal injection of [15N]ammonium salt, 40–50% of the N entering the plasma urea pool arose from ruminal ammonia; 26% of the 15N injected was excreted in urinary N.8. Although 5.1g N/d as urea was degraded apparently in the digestive tract, only 1.2g N/d appeared in ruminal ammonia; it is suggested that the remainder may have been degraded in the lower digestive tract.9. A large proportion of the urea N entering the digestive tract is apparently degraded and absorbed and the ammonia incorporated in the pools of nitrogenous compounds that turn over only slowly. This may be a mechanism for the continuous supply to the liver of ammonia for these syntheses.10. There was incorporation of 15N into bacterial fractions isolated from rumen contents after intraruminal and intravenous administration of [15N]ammonium salts and [15N]urea respectively.11. A model for N pathways in sheep is proposed and, for this diet, many of the pool sizes and turn-over rates have been either deduced or estimated directly.

On the calculation of heat production from open-circuit calorimetric measurements

Abstract: 1. The equation used for calculating heat production of ruminant animals is expressed in a new form, convenient for application to open-circuit calorimetry.2. It is shown that in open-circuit calorimetry the possible error involved in making the assumption that respiratory quotient is equal to unity is small compared with the possible error involved in neglecting methane production.3. In open-circuit calorimetry heat production can be predicted with accuracy to within ± 2% solely from the measurement of oxygen concentration and ventilation rate.

The effect in sheep of physical form on the sites of digestion of a dried lucerne diet. 2. Sites of nitrogen digestion.

Abstract: I . The effect of altering the physical form of a regrowth crop of dried lucerne (Medicago sutivu L. var. Chartuinvilliers) on the sites of organic matter, energy and carbohydrate digestion was studied with sheep fitted with re-entrant cannulas at the proximal duodenum and at the terminal ileum. 2. Chopped, cobbed, and ground and pelleted diets with moduli of fineness of 3.~~2.7 and 1-5 respectively were prcpared from the same high-temperature dried crop and given twice daily to sheep at a level of intake of 910 g dry matter/d. 3. Physical form did not affect the apparent digestibility of the organic matter. On the cobbed and pelleted diets losses of digestible organic matter before the small intestine were significantly lower (P < 0.05; P < 0.001 respectively) and losses in the small intestine were significantly higher ( P < 0 .05) than for the chopped diet. 4. Apparent digestibility of the gross energy of the three physical forms was similar, but the flow of energy into, and digestion within, the small intestine were markedly greater (P < 0.05) for the ground and pelleted diet than for either the chopped or cobbed diet, for which the values did not differ. Energy digestion in the caecum and colon was similar for the three physical forms. 5. Total cellulose and hemicellulose digestibilities were not affected by processing, but the proportion of the digestible cellulose and digestible hemicellulose digested in the fore-stomachs of sheep given the ground and pelleted diet (63 and 55 % respectively) was less than for the chopped diet (85 and 68 yo). The digestibility of the cobbed diet was intermediate. Digestion in the caecum and colon compensated for these differences in digestion of cellulose and hemicellulose in the fore-stomachs. 6. Volatile fatty acid (VFA) concentration in the rumen liquor was lower in sheep given ground, pelleted lucerne than in those on the chopped diet, but the VFA proportions were very similar. The implications of the change in site of energy and carbohydrate digestion with grinding and pelleting are discussed.

Quantitative studies on nitrogen metabolism in the bovine rumen. The rate of proteolysis of casein and ovalbumin and the release and metabolism of free amino acids.

Abstract: 1. Monozygous twin cattle with permanent rumen fistulas were used to measure the rate of degradation of casein and ovalbumin. One twin was used as a control and the other had protein administered by fistula about 4.75 h after eating a standard ration. 2. Casein was rapidly degraded with a half-life in the range 5.6–21.5 min, with the formation of peptides, free amino acids and finally ammonia. Up to 43% of the casein nitrogen was found as ammonia in the rumen fluid. Most of the amino acids present in casein were found in the free state in the rumen fluid to an extent of less than 7%, but valine, leucine, isoleucine and lysine were present as 25, 27, 21 and 38% respectively of the amounts present in the casein administered. 3. When acid-hydrolysed casein was given, ammonia was rapidly formed, the maximum amount found in the rumen being equivalent to 39% of the casein N. The individual amino acids were rapidly broken down except for valine, leucine, isoleucine and lysine of which synthesis in addition to degradation may occur. 4. Ovalbumin was degraded slowly with a half-life of 175 min, which was reduced to 132 min by feeding the cattle with ovalbumin for 5 d. Ammonia was produced slowly. 5. When added together the two proteins were degraded in the rumen independently at their own rates. 6. δ-Amino-n-valeric acid was produced in large quantity when casein or casein hydrolysate was degraded in the rumen.

Absorption of labelled vitamin A in children during infection.

Abstract: 1. The intestinal absorption of [11,12 3H2] retinyl acetate was studied in five apparently normal children, eight children with respiratory infection and three with gastroenteritis.2. The absorption of vitamin A was significantly lower in children with respiratory infection or gastroenteritis than in normal children.3. In the light of these observations, it is suggested that repeated attacks of infections may significantly contribute to the prevalence of vitamin A deficiency in children of poor communities.

The effect in sheep of physical form and stage of growth on the sites of digestion of a dried grass. 1. Sites of digestion of organic matter, energy and carbohydrate.

Abstract: I . The efyect of grinding and pelleting artificially dried S 24 perennial rye-grass (LoZium perenne L.) cut at two stages of maturity on sites of digestion of organic matter, energy and carbohydratc were studied in sheep with re-entrant intestinal cannulas fitted at the proximal duodenum and terminal ileum. Chopped and pelleted grasses at both stages of maturity were each given at 900 g dry matter/zq h to each of five sheep; the two forms of the early-cut grass were also given at 1400 g dry msltter/zq h each to four of the fivc shccp. 2. With the carly-cut grass, grinding and pelleting caused a depression in digestibility of organic matter (low level, P < 0 . 0 5 ; high level, P < woor), lo\\vered the proportion of the digested organic matter disappearing before the small intestine (low level only, P < 0.05) and significantly increased that disappearing in the caccum and colon (low level, P 4 0.05 ; high level, P < OYJOI). Increase in stagc of maturity significantly depressed digestibility of organic matter ( P < 0001) with both forms of grass and, with the chopped form, significantly increased the proportion of digestible organic matter disappearing in the caecum and colon (P < 0.01). Increase in level of feeding of the pelleted, early-cut grass significantly lowered organic matter digestibility ( P < O . O ~ ) , reduced the proportion of digestible organic matter disappearing in the small intestine ( P 4 005) and increased that occurring in the caecum and colon ( P < 0.05). 3. With the early-cut grass, grinding and pelleting caused 3 depression in digestibility of gross energy only at the higher level of intake ( P < O O I ) , and reduced the proportion of apparently digestible energy disappearing before the small intestine (IOW level, P < 0.001 ; high level, P < 0.05). Only with the chopped form did stagc of maturity affect sites of energy digestion; with the more mature grass disappearance of energy in the reticulo-rumen declined (P < 0.01) and that in the caecum and colon increascd (P < 0301). The effects of level of feeding were similar to those observed for organic matter. 4. With the early-cut grass, and at both levels of intake, digcstibilities of cellulose and hemicellulose were depressed by grinding and pelleting (P < O.OOI), as were the proportions of digestible cellulose and hemicellulose disappearing before the small intestinc (P < 0.001). Thc proportions of these digestible fractions disappearing in the caecum and colon werc significantly increased (P < 0.001). Increase in stage of maturity depresscd cellulose digcstibility (P i 0.001) of the chopped but not pelletcd grass and depressed hemicellulose digestibility of both forms (P < 0001). The effects of increase in maturity at harvest on sites of digestion depended upon the form of the grass, With the chopped form, as stage of maturity increased, the proportion of digestible hemiccllulose disappearing in the reticulo-rumen fell ( P < 0.01) and that, and the proportion of digestible cellulose, disappearing in the caecum and colon increased ( P < 0'01 and P < 0.05 respectively); with the pelleted form, the proportions of digcstible cellulose and digestible hemicellulose disappearing in the reticula-rumen increased ( P < 0.001 and P < OOI respectivcly) whereasthosedisappearingin the caecum and colon declined ( P < 0.01). With the pelleted, early-cut grass increase in intake resulted in a depression in cellulose and hemicellulose digestion ( P < 0 0 5 and P < 0.001 respectidy) and increased proportional losses of digestible cellulose and digestible hcmiccllulose in the caecum and colon ( P 4 0'01 and P < 0.05 respectively).

Changes from birth to maturity in the pattern of distribution of lactase and sucrase activity in the mucosa of the small intestine of pigs

Abstract: I . Measurements were made of changes in lactase and sucrase activity of homogenates of small intestine mucosa of sixty-one pigs varying in age from newborn to mature animals. 2. From each pig, samples for enzyme determination were taken from siu sites along the small intestine. These sites were at 5,20,40,60, 80 and 95 yo of the length of the small intestine, measured from the pylorus. 3. Lactase activity was present at high levels in the newborn pig, the maximum being found at the 20 % site. Between birth and 8 weeks of age there was a fall in the amount of activity in the mucosa of the small intestine. In older pigs the levels of mucosai lactase activity were not greatly different from those found in 8-week-old pigs, although the distribution along the small intestinc tended to change with advancing age. 4. Sucrase activity was found only once in thirty-six samples from the small intestine of six newborn pigs, but was present in all six pigs sampled at I week of age. Levcls of activity continued to rise until maturity. Maximum activity was found at the 20 or 40 % site in the younger pigs (1-8 weeks of age). In the older pigs, high activity was found at a wider range of sites, the peak of activity generally being at the 40 and 60 y/o sites.

The effect in sheep of physical form and stage of growth on the sites of digestion of a dried grass: 2. * Sites of nitrogen digestion

Abstract: I . The effect of grinding and pelleting S 24 perennial rye-grass (Lolium perenne L.), harvested at two stages of maturity and artificially dried, on the sites of digestion of nitrogenous constituents was studied with sheep equipped with a fistula into the rumen and re-entrant cannulas at the proximal duodenum and terminal ileum. Chopped and pelleted grasses at both stages of maturitywere each givcn at goo g dry matter ( D M ) / z ~ h to each of five shcep; the two forms of the early-cut grass were also given each to four of the five sheep at 1400 g D M / Z ~ h. 2. The pelleting process significantly depressed apparent digestibility of total nitrogen in both grasses (P < 0.05). For the early-cut grass neither physical form nor level of feeding had any significant cffect on N retention; for the medium-cut grass N retention was significantly higher (P < 0.05) when thc pelletcd form was given. N retention was significantly lower on the medium-cut grass (P < 0.05) than on the early-cut grass. 3. For individual amino acids the greatest relative increases (intake = 100) at the proximal duodenum were found for mcthionine and cysteine/cystine ( P < 0.001) on all six diets, together with tryptophan (P at least < 0.01) and lysine (P at least < 0.05) on five of the diets, and including histidine on the early-cut diets ( P at least < 0.01) . At the low level of feeding, incrcase in stage of growth at cutting significantly dcpressed the relative amounts of phenylalanine, lysine, serine ( P < 0.05), histidine, aspartic acid and tyrosine ( P < 0.01) entering the small intestine, and increased those of tryptophan ( P < 0.05). Pelleting of the early-cut grass significantly increased the amounts of methionine entering the small intestine compared with feeding it chopped (P

The digestion of heather (Calluna vulgaris) by red grouse (Lagopus lagopus scoticus)

Abstract: 1. In the wild, red grouse live largely on heather, a high-fibre (25%), low-protein (7%) food. Digestibility trials were carried out under semi-natural conditions, with magnesium as a digestibility marker. Two trials were done, one in autumn and one in spring. 2. Digestibility of the dry matter varied from 21 to 30% and metabolizable energy from 1.1 to 1.6 kcal/g. These variations were inversely related to intake and could partly be accounted for by facultative variations in holocellulose and lignin digestion. 3. Digestion of soluble carbohydrates, protein (measured as α-amino-nitrogen) and holocellulose varied between trials according to the initial concentration in the food. The digestibility of soluble carbohydrate was high (78–83%) in autumn (16% in food) and low (61–66%) in spring (11% in food) and that of protein was relatively low (24–31%) in autumn (6% in food) and high (42–48%) in spring (7% in food). Digestibility of crude fat was 30–33% for four birds and 20% for one bird. 4. By comparison with poultry, voluntary intake of dry matter was very high relative to body-weight and intake of energy appeared to be adequate. None the less, all birds lost weight during the trials, presumably for reasons other than energy shortage. 5. Urate excretion increased in parallel with body-weight losses, but formed only 2% of the total N output at low weight losses, in which event the main nitrogenous compounds in the droppings were α-amino N (presumably largely from undigested protein), ammonium salts and ornithuric acid. 6. The ornithuric acid was presumably a detoxication product of prolignins and possibly tannins and other polyphenols. Its excretion by grouse corresponds to the excretion of hippuric acid by ruminants.

The role of amino acid oxidation in causing ‘specific dynamic action’ in man

Abstract: 1. The increase in metabolic rate which occurs after ingestion of protein (the so-called ‘specific dynamic action’) has been attributed to the energy requirements for urea synthesis and amino acid degradation.2. We have tested, in normal adult subjects, the effect of meals which increase or decrease the rate of urea production, and our results do not substantiate this hypothesis.3. The difficulties of accurate measurement of resting metabolic rate are discussed.4. The term ‘specific dynamic action’ is inappropriate since the effect is not specific. We believe that it may prove to be a reflection of protein synthesis rather than of protein catabolism.

Effects of dietary mineral acids on voluntary food intake, digestion, mineral metabolism and acid-base balance of sheep.

Abstract: I . A pelleted grass meal diet alone (control) or supplemented with hydrochloric acid, sulphuric acid or a I : I mixture of these acids, at 320 mequiv./kg, was offered ad Zib. to eight sheep in a double 4 x 4 Latin square design for 20 d. 2. The HCI and HCl-H,SO, treatments each reduced food intake of the sheep by 19 \"/o and the H,SO, treatment reduced it by 3076,. Avcrage daily intake of acid was 397, 333 and 299 mequiv. on the HCI, HCl-H,SO, and H,SO, treatments respectively. 3. Rumen fluid pH was decreased by each acid treatment by 0'1-0'2 units without any appreciable changes in total or individual volatile fatty-acid concentrations. Dry-matter digestibility was slightly increased by each acid treatment. 4. Blood pH, plasma bicarbonate and blood base excess were decreased by each acid treatment; sulphateconcentration in serumwas increased bythe HC1-H,SO,and H,SO, treatments. 5 . In urine the acid treatments decreased the pH from a control value of 8.0 to approximately 6.0; associated with this was a large decrease in urinary bicarbonate and a large increase in urinary ammonia-nitrogen and calcium excretions. 6. The chloride and sulphur contributed by the acid treatments were almost entirely absorbed and excreted in the urine. Each acid treatment caused a negative balance of Ca equal to the increase in urinary Ca. Effects on other minerals were small. 7. The effect of the HCl and the HCl-H,SO, treatments on voluntary food intake is ascribed to metabolic acidosis and of the H,SO, treatment to excess dietary sulphate-S.

Quantitative intestinal digestion of nitrogen in sheep given formaldehyde-treated and untreated casein supplements.

Abstract: 1. In two experiments, sheep prepared with a rumen cannula and with re-entrant cannulas in the duodenum and ileum were continuously fed on diets of dried grass, dried grass plus formalin-treated casein, or dried grass plus untreated casein. Paper impregnated with chromic oxide was given once daily via the rumen fistula. 2. In ten 24 h collections of digesta entering the duodenum and eleven 24 h collections of digesta reaching the ileum of sheep given dried grass, there were highly significant correlations between the 24 h flows of Cr marker and the corresponding flows of dry matter, organic matter, nitrogen, gross energy, hemicellulose and cellulose ( P 3. Daily amounts of non-ammonia N and of individual amino acids entering and leaving the small intestine and of total N excreted in faeces and urine are given. 4. Net retention of supplementary N was 36% when the supplement was administered as formalin-treated casein, but only 17% when it was administered as untreated casein. 5. Formalin treatment of casein significantly increased the daily amounts of non-ammonia N entering the small intestine ( P P 6. Apparent absorption of amino acids from the small intestine was significantly greater ( P

Effect of dietary changes on intestinal absorption of L-methionine and L-methionyl-L-methionine in the rat.

Abstract: 1 The absorption rates of L-methionine and L-methionyl-L-methionine (dimethionine) from the upper jejunum and lower ileum of the rat were studied in vivo after different dietary treatments Rates were expressed per unit gut length and per unit gut weight; the former was considered to be the more satisfactory under the different dietary conditions2 The dietary treatments were either short-term (10 d) or long-term (40–84 d)3 The rate of absorption of methionine increased in the jejunum after a restricted dietary intake, a high-protein diet or a high-methionine diet, but decreased after long-term protein deprivation Short-term dietary restriction had a similar effect on methionine absorption in jejunum and ileum, though less pronounced in the latter The rate of absorption of dimethionine was less influenced by dietary changes than that of methionine4 Under all conditions studied, the absorption rate of methionine was greater when presented as the dipeptide than when presented as the equivalent amount of free amino acid This confirms that dimethionine is taken up intact from the intestinal lumen, and it seems likely that there are different mechanisms of mucosal uptake for methionine and its dipeptide

The capacity of the mature cow to lose and recover nitrogen and the significance of protein reserves

Abstract: 1. Six experiments were undertaken with mature, dry, non-pregnant cows to determine the capacity to lose and recover nitrogen and to study the significance of the labile and total protein reserves. 2. It was concluded that, without altering its ability to reach N equilibrium, the mature cow is able to store and lose large amounts of body proteins (certainly more than 15 kg), when its N and energy intakes are greatly varied. The repletion or depletion of protein reserves can occur over a long period of time (sometimes more than 5 months). Total protein reserves include a very labile part. This part is more rapidly lost during fasting than during feeding on low-protein diets; it can be used to meet temporarily the energy requirements of the animal. 3. N balance and body-weight gains were generally very well correlated.

Fermentation of various glycolytic intermediates and other compounds by rumen micro-organisms, with particular reference to methane production.

Abstract: Experiments with a small-scale artificial rumen have shown that of forty-two compounds tested the majority were fermented, as judged by the production of volatile fatty acids, but methane production was associated only with the fermentation of formate, certain hydroxy-acids, pyruvic acid, primary alcohols (methanol, ethanol, propanol and butanol), glycerol and methyl compounds. With primary alcohols there was a stoichiometric relationship between methane production and the oxidation of the alcohols to the corresponding acids.The fermentation of rhamnose and 1,2-propanediol was studied in detail. With both compounds there was a temporary accumulation of lactic acid and a continuous net production of propionic acid. The initial rate of acetate production was rapid with rhamnose but decreased subsequently, whereas propionate continued to increase. With propanediol the net rate of production of acetate was slow at first and then increased. There was no increase in the production of butyric acid with either rhamnose or propanediol, and the endogenous methane production was inhibited by 20–40%. There was evidence for the formation of an unidentified compound during fermentation of rhamnose and propanediol.

The influence of malnutrition on the postprandial metabolic rate and respiratory quotient.

Abstract: 1. Pre- and post-prandial metabolic rates were measured in twelve malnourished Jamaican infants.2. On admission to hospital, minimal increase in postprandial metabolic rate were found, whereas during the recovery phase when growth was rapid, inreases in postprandial metabolic rate of up to 38% occurred.3. After recovery only the five children who were still gaining weight at a rate of more than 4 g/kg body-weigh. d continued to show a substantial increase in postprandial metabolism.4. A highly significant correlation was found between growth rate and the increase in postprandial metabolic rate.5. Marked differences existed in the respiratory quotient measured 4 h after the last meal, the values being low on admission and high during the phase of rapid growth.6. After a test meal, the respiratory quotient rose sharply both innewly admitted and in recovered children, but fell slightly when the children were studied during the phase of rapid growth.

The influence of the intestinal microflora on disaccharidase activities in the chick.

Abstract: 1 Maltase sucrase, palatinase (the enzyme that hydrolyses palatinose, ie 6-o-α-D-gluco-pyranosyl-D-fructose) and lactase activities were measured in the small and large intestines of germ-free and conventional chicks given either a diet of purified ingredients or a practical chick mash2 With the purified diet there were no differences in body-weight or small intestinal disaccharidase activities between germ-free and conventional chicks With the chick mash the germ-free birds were heavier and had higher total amounts of maltase, sucrase and palatinase activities in the small intestine than did their conventional controls When disaccharidase activities were expressed in terms of body-weight there were no differences between birds in the two environments Enzyme activities were consistently higher in the birds given chick mash3 Inclusion of milled fibre in the purified diet did not increase the weight or disaccharidase activities of the small intestine in either environment4 Lactase was virtually absent from the small intestine of birds in both environments and from the large intestine of germ-free birds There was appreciable lactase activity in the large intestinal contents of conventional chicks, and it was increased by inclusion of lactose in the diet5 When lactose was the sole source of carbohydrate the birds grew poorly but mortality rate was less among conventional compared with germ-free chicks6 It was concluded that the presence of micro-organisms has no direct effect on disaccharidase production in the small intestine of the chick Microbial lactase is present in the large intestine, and at least some of the products of its action can be utilized by the bird

The effect in sheep of physical form on the sites of digestion of a dried lucerne diet. 1. Sites of organic matter, energy and carbohydrate digestion.

Abstract: I . The effect of altering the physical form of a regrowth crop of dried lucerne (Medicago sutivu L. var. Chartuinvilliers) on the sites of organic matter, energy and carbohydrate digestion was studied with sheep fitted with re-entrant cannulas at the proximal duodenum and at the terminal ileum. 2. Chopped, cobbed, and ground and pelleted diets with moduli of fineness of 3.~~2.7 and 1-5 respectively were prcpared from the same high-temperature dried crop and given twice daily to sheep at a level of intake of 910 g dry matter/d. 3. Physical form did not affect the apparent digestibility of the organic matter. On the cobbed and pelleted diets losses of digestible organic matter before the small intestine were significantly lower (P < 0.05; P < 0.001 respectively) and losses in the small intestine were significantly higher ( P < 0 .05) than for the chopped diet. 4. Apparent digestibility of the gross energy of the three physical forms was similar, but the flow of energy into, and digestion within, the small intestine were markedly greater (P < 0.05) for the ground and pelleted diet than for either the chopped or cobbed diet, for which the values did not differ. Energy digestion in the caecum and colon was similar for the three physical forms. 5. Total cellulose and hemicellulose digestibilities were not affected by processing, but the proportion of the digestible cellulose and digestible hemicellulose digested in the fore-stomachs of sheep given the ground and pelleted diet (63 and 55 % respectively) was less than for the chopped diet (85 and 68 yo). The digestibility of the cobbed diet was intermediate. Digestion in the caecum and colon compensated for these differences in digestion of cellulose and hemicellulose in the fore-stomachs. 6. Volatile fatty acid (VFA) concentration in the rumen liquor was lower in sheep given ground, pelleted lucerne than in those on the chopped diet, but the VFA proportions were very similar. The implications of the change in site of energy and carbohydrate digestion with grinding and pelleting are discussed.

Energy intake and expenditure in 1-3-year-old Ugandan children living in a rural environment.

Abstract: I . In a prospective study of Ugandan children during the 2nd and 3rd years of life, energy intakes 30 : / A bclow the rccommendcd level merc frequently found. Despite this the children gained weight at rates similar to those of healthy English children. 2. In view of the low-energy intakes, the activity of the children was studied using a modified form of the diary method of recording activitics. European children living under the same climatic conditions were also studied by this method. 3. The Ugandan children spent significantly less time than the European children in activities involving a relatively high rate of energy expenditure such as walking and running. 4. This disparity could account for a difference in energy expenditure of the order of 20 kcal (84 kJ)/kg bodp-weight per d. Thc implications are discussed.

Effects of isocaloric exchange of dietary sucrose and starch on fasting serum lipids, postprandial insulin secretion and alimentary lipaemia in human subjects.

Abstract: 1. Fasting serum cholesterol and triglyceride, and post prandial insulin secretion and lipaemia were measured in human subjects in a metabolic ward, who were given an ordinary diet (diet 1) in which the sucrose was isocalorically replaced by starch (diet 2) or vice versa. The subjects were nine healthy normolipaemic adult males. In eight of these subjects the effect of sucrose calorie reduction (diet 3) on fasting serum lipids was also studied.2. When starch replaced sucrose, there were no singnificant differences in fasting serum lipid concentrations or immunoreactive insulin or in the insulin response and alimentary lipaemia after a standard mixed breakfast.3. Serum triglyceride concentration fell and cholesterol concentration rose during the period of sucrose (and calorie) restriction.4. After lunch and supper on the first two diets (when different carbohydrates were given) the lipaemic response was larger and the insulin response smaller after meals containing sucrose.5. Thus, there was no difference between concentrations of fasting serum lipids when starch replaced sucrose at 23% total calories, but the concentrations of serum triglycerides were higher after individual mixed meals containing sucrose.6. There were no significant differences in the fatty acid patterns of serum lipids on the different diets.

Some effects of rumen ciliate protozoa in cattle given restricted amounts of a barley diet.

Abstract: 1. Two pairs of Friesian steers were changed from ad lib. to restricted intake of a pelleted barley diet and were maintained on this latter intake for periods of 18 or 25 weeks. The restricted level of intake was 70 g/kg0.73 and was adjusted weekly according to individual live weights. The daily allowance was given in three equal feeds during day-time.2. After an initial period of 9 weeks on the restricted diet, during which all four animals were kept free of rumen ciliate protozoa, one member of each pair was given an inoculum of rumen ciliates. Eight weeks later, the ciliate-free member of the younger pair of steers was similarly inoculated. Observations were made on the rumen bacterial and protozoal populations and on changes in rumen pH and volatile fatty acids (VFA) throughout each treatment period. The concentrations of urea and haemoglobin in blood and of glucose and amino acids in plasma were examined on one occasion in each animal.3. In the absence of ciliates, restriction of intake resulted in rumen pH values and molar proportions of VFA similar to those normally encountered on an ad lib. intake of a barley diet. A decrease in bacterial numbers and certain minor changes in bacterial types were observed on changing from ad lib. to restricted intake but the resultant population under ciliate-free conditions was basically the same as that found later in the faunated animals. In culture, organisms of the genus Bacteroides were predominant.4. Large populations of rumen ciliates were established in each animal inoculated. Relative to the ciliate-free periods, the presence of ciliates resulted in an increase in rumen pH, a reduction in total VFA concentration and a decrease in the ratio of propionic to butyric acid in rumen fluid. It is concluded that these changes are a direct effect of ciliate activity.5. Conditions within the rumen remained more stable from day to day when large ciliate populations were present than when ciliates were absent. In one animal, spontaneous fluctuations in ciliate number were accompanied by corresponding changes in rumen pH and VFA proportions.6. Significant differences were observed between faunated and ciliate-free animals in the concentration urea in blood and of glucose in plasma; only minor differences were noted in blood haemoglobin and plasma amino acid concentrations.

Nutrient stores in human foetal livers.

Abstract: 1. Liver composition and hepatic nutrient stores in foetuses born to mothers belonging to a low socio-economic group of the population were determined.2. The contribution by the liver to body-weight and the concentration of water and nitrogen in liver at different gestational ages were relatively constant.3. Total iron and copper contents of the liver were in the normal reported range but the ferritin content was considerably lower in the present investigation.4. Hepatic stores of vitamin A, vitamin B12 and folate were lower than the values that have been reported elsewhere.5. It is suggested that inadequate stores of iron, vitamin A, vitamin B12 and folate in these infants may predispose them to the early development of some deficiency diesease.

Composition of the human foetus

Abstract: 1. The body composition was determined of forty-one fetuses of different gestational ages born to mothers belonging to a low socio-economic group of the population.2. With increasing gestational age the water content fell from 88% at 28 weeks to 76% at term; the fat content increased from 2.1% to 11.2% and the protein content increased from 6.9 to 9.3%.3. The changes in body composition were more closely related to body-weight than to gestational age.4. The calcium, Phosphorus and magnesium contents of the body per unit fat-free weight progressively increased with gestational age, and at term the values appeared to be considerably lower than those reported in the literature. The Ca:P ratio was constant at different body-weights.5. The body iron content per unit of fat-free weight increased marginally with increasing gestational age. The value was almost 30% lower than the values reported from elsewhere.6. It is suggested that chemical composition and nutrient stores of the developing foetus can be considerably influenced by the state of maternal nutrition.

The effect of intravenous infusions of sterculic acid on milk fat synthesis.

Abstract: 1. The effects of intraduodenal infusions of sterculic acid, a naturally occurring inhibitor of desaturase activity, on the yield and composition of milk were examined in a lactating goat.2. Sterculic acid administration increased the percentage of stearic acid in milk fat, reflecting inhibition of mammary desaturase activity. Milk yield was not affected, but milk fat output decreased. Possible explanations are discussed.3. No evidence was obtained for an alternative pathway of oleic acid synthesis from acetate.

The course of digestion of different food proteins in the rat. 3. The absorption of proteins given alone and with supplements of their limiting amino acids.

Abstract: I. Single meals of casein, a-protein, a commercial soya-bean assay protein, wheat gluten and zein (243 mg nitrogenlroo g body-weight) were given with and without Supplements of their limiting amino acids to groups of rats housed in anti-coprophagy cages, after an 18 h fast. At intervals after feeding, rats were anaesthetized, sampies of portal and cardiac blood were taken for the determination of free amino acid concentrations in dcproteinized plasma (PA4 concentrations), and the contents of the gastro-intestinal tract were collected and analysed. z. The different proteins left the stomach at different rates and gave differcnt concentrations of nitrogen and dry matter in the small intestine contents. Supplementary amino acids caused no alteration in the tota! rate of passage, digestion or absoq. 'tion. . 3. The supplementary amino acids were gencrally ahsorbcd more rapidly than amino acids derived from the protein. 4. It was not possible to use the changes in PAA concentrations as criteria to detect enhanced utilization of proteins resulting from the addition of amino acids. A fall in 1'AA concentrations upon adding these supplemcnts, indicating increiised protein synthesis, was demonstrated for only one test protein, gluten.