1. Measurements were made of the nitrogen and energy balances of pigs of 30, 60 and 90 kg given a conventional diet at various daily rates.

2. Body protein synthesis was estimated from the irreversible loss of leucine from the blood following the infusion of [1-14C]leucine, and from the oxidation of the labelled amino acid.

3. Protein synthesis (g/d) increased by 2.17 for each 1 g increase in daily protein accretion and by 1.55 for each 1 g increase in daily protein intake.

4. At 30 kg, pigs close to energy equilibrium synthesized 270 g protein daily compared with 406 g and 512 g when their ration supplied twice and three times their maintenance requirement.

5. There was a close correlation between the daily urinary excretion of urea + ammonia and total amino acid catabolism estimated from the catabolism of leucine, but the latter underestimated the observed excretion by 2.5 g N/d.

6. The results imply that protein turnover accounts for only a proportion of the heat production associated with protein deposition.

1. The effect of energy and protein intake on the nitrogen and energy utilization and carcass composition of artificially-reared pigs was studied between 8 and 32 d of age in an experiment employing a 5 × 3 × 2 factorial design. The factors were initially energy:N value (I) (250, 355, 460, 565 or 670 kJ/g N), rate of increase of I (R) at 8 d intervals (0, 12.5 or 25%) and plane of nutrition (three times daily to appetite or 75% of this intake).

2. The range of energy:N values was obtained by formulating five diets based on dried skim milk, lactose and casein and feeding appropriate combinations of two diets.

3. The metabolizable energy (ME) intake, carcass dry matter (DM) content, carcass protein gain and carcass fat gain exhibited significant (P < 0.001) quadratic responses to I.

4. The carcass fat content in the DM increased from 200 to 342 g/kg (P < 0.001) and the carcass crude protein (N × 6.25) content decreased from 657 to 519 g/kg with increasing level of I (P < 0.001). The fat and protein contents were 309 and 556 g/kg and 242 and 610 g/kg respectively on the high and low plane of nutrition (PN) and were significantly different (P < 0.001).

5. There was a significant I × R interaction in relation to carcass protein gain with the maximum gain occurring at 460 kJ/g N when I was constant and at 355 kJ/g N when R was 25% per 8 d.

6. The proportion of apparent digested N intake retained (N retention (NR): apparent digested N (ADN)) was significantly (P < 0.001) affected by all three factors and there were significant I × R (P < 0.001), I × PN (P < 0.01) and R × R × PN (P < 0.01) interactions. The maximum value of NR:ADN was 0.80.

7. Carcass fat gain and carcass energy gain exhibited quadratic responses to I reaching maximum values at 460 kJ/g N. The energy content of the live-weight gain increased linearly (P < 0.001) from 5.79 to 7.90 MJ/kg with increasing level of I. PN and R also produced significant (P < 0.001) responses the means being respectively 7.52 and 6.39 MJ/kg on the high and low PN and 6.55, 6.94 and 7.38 kJ/kg with increasing value of R.

8. Multiple regression analysis of ME intake on live-weight (W), protein gain (PG) and fat gain (FG) yielded the equation: <m:math><m:mrow><m:mtext>ME</m:mtext><m:mo stretchy="false">(</m:mo><m:mtext>MJ</m:mtext><m:mo stretchy="false">)</m:mo><m:mo>=</m:mo><m:mn>0</m:mn><m:mo>.</m:mo><m:mn>644</m:mn><m:msup><m:mtext>W</m:mtext><m:mrow><m:mn>0</m:mn><m:mo>.</m:mo><m:mn>75</m:mn></m:mrow></m:msup></m:mrow><m:mo>+</m:mo><m:mn>32</m:mn><m:mo>.</m:mo><m:mn>6</m:mn><m:mtext>PG</m:mtext><m:mo>+</m:mo><m:mn>48</m:mn><m:mo>.</m:mo><m:mn>2</m:mn><m:mtext>FG</m:mtext><m:mo>.</m:mo></m:math>

This result is discussed in relation to published values for the energy requirements of the young pig.

1.Fifteen female farmers (aged 18–47 years) from two villages of the Mossi Plateau in Upper-Volta participated in a survey in which their daily activity pattern and their energy expenditure were assessed. Eight of the subjects were investigated twice, in March (dry season) when there is no agricultural activity, and in July–August (rainy season) when heavy physical work is performed: mostly hoeing, weeding and replanting sorghum (Sorghum vulgare) and millet (Pennisetum typhoïdes).

2. The mean height was 1.57 m and the mean weight 50.6 kg. The average percentage of body fat, calculated from skinfold thickness, was comparable to that of European females but the triceps skinfold was more than 60% below the standard value (Jelliffe, 1969). The type of activities and the period of time spent on each activity changed significantly with the season. The mean energy output rose from 9.7 MJ (2320 kcal) in March to 12.1 MJ (2890 kcal) in July–August for a 55 kg standard weight.

3. In this paper, the extent of both the dally activity pattern of women living in a subsistence agriculture and their energy output is estimated. The results suggest that during the rainy season, the energy requirements of female farmers are much higher than usually estimated.

1. Semi-synthetic diets containing 200 g protein/kg were meal-fed for 1.5 h to groups of rats. The contents of the whole small intestinal tract were collected and the amount of soluble calcium was determined.

2. In the rats given 200 g casein/kg diet, formation of a fraction containing macrophosphopeptide in the small intestine was confirmed by gelfiltration of the intestinal contents on Sephadex G-25. However, this macrophosphopeptide fraction was not found when casein alone was fed.

3. In the intestinal contents at 2.5 h after ingestion, the amounts of both soluble Ca and phosphorus were significantly higher in rats fed the casein diet than in those fed diets containing egg albumin, isolated soyabean protein or an amino acid mixture. However, the amount of insoluble Ca was least in rats fed the casein diet.

1. The heat production of groups of pigs, weaned at 10 d of age, was determined in an open-circuit respiration chamber at various ages between 10 and 33 d at temperatures above and below the lower critical temperature (Tcl).

2. The heat production was lowest on the second or third day post weaning when pigs were given feed increasing by 25 g/pig per d from day 2. There was a marked diurnal pattern in heat production, the lowest values being recorded between 24.00 and 08.00 h.

3. The mean thermal conductance (H/ΔT, kJ/h per m2 per °ΔT, where His total heat production, m2 is the surface area calculated as 0.097 W kg0.633 (Brody, 1945) and °ΔTis the difference between rectal temperature, taken as 39°, and air temperature) below Tcl was calculated as 18.0, 16.9, 18.5 and 21.2 respectively at 10, 17, 24 and 31 d of age. Maximum values of H/ΔT obtained during feeding periods were. on average, 4.5 kJ/h per me per °ΔT higher than the mean values.

4. The maximum value for Tcl during the immediate post-weaning period was 25.9°. The mean Tcl at 17, 24 and 31 d were respectively 21.7, 18.4 and 18.6° for pigs fed almost to appetite.

1. Lee Index (weight (g0.33)÷ nasoanal length (mm)), density, body water and proportional weight of the gonadal fat pad were tested as estimates of body fat in a normal population of mice and a population which included obese mice.

2. In a normal population only body water and fat-pad weight correlated significantly with body fat.

3. In a population of normal and obese mice all four indices correlated significantly with body fat.

4. Lee Index had little advantage over weight: length as an estimate of body fat, and density did not correlate well enough to be used as a method of estimation.

5. Proportional weight of the gonadal fat pad is recommended as a simple reliable estimate of body fat in normal or obese mice.

Two experiments were conducted to study the digestion of nitrogenous constituents in the rumen, small intestine and caecum and colon of sheep given diets of grass silage or grass silage and barley. Three silages were used. One was made from first-harvest grass in the spring and the others from regrowth grass cut in either early autumn or late autumn. All were of perennial ryegrass (Lolium perenne) and were preserved with formic acid.

Expt 1 involved a comparison between the spring silage given alone (644 g dry matter (DM)/d) and the spring silage supplemented with barley (151 g DM/d). The intakes (g/d) of total nitrogen for the silage diet and for the supplemented diet were 14.89 and 17.36. Corresponding values (g/d) for N passage were 15.55 and 18.53 (P < 0.01) at the duodenum, 6.01 and 7.09 at the ileum and 5.06 and 5.52 in the faeces. The barley supplement had no significant (P < 0.05) effect on rumen ammonia-N- concentration.

Expt 2 involved a comparison between the two autumn-cut silages each offered at a level of feeding of approximately 700 g DM/d. The intakes (g/d) of total N for the early-cut silage and for the late-cut silage were 21.67 and 15.62 respectively. Corresponding values (g/d) for N passage were 17.10 and 16.96 at the duodenum, 6.65 and 6.80 at the ileum and 4.5 and 5.22 in the faeces. The concentration of NH3-N in the rumen was significantly (P < 0.001) higher with the early-cut silage than with the late-cut silage.

In both experiments the rates of bacterial crude protein (N × 6.25) synthesis in the rumen, estimated using α, ε-diaminopimelic acid as a marker, were low, 142 and 161 g crude protein/kg organic matter apparently digested in the rumen for the spring silage and the spring silage and barley diets respectively, and 68 and 103 g crude protein/kg organic matter apparently digested in the rumen for the early-cut autumn silage and the late-cut autumn silage respectively. For all diets there was a relatively low contribution of bacterial crude protein to the duodenal passage of crude protein and the amounts of individual amino acids ingested in the diets had a marked influence on the amino acids passing to the duodenum and as a consequence on the mixture of amino acids taken up from the small intestine.

The results are discussed in relation to the nutritive value of silage N for ruminants.

Two experiments were conducted to study the digestion of organic matter, gross energy and carbohydrate constituents in the rumen, small intestine and caecum and colon of sheep given grass silage diets. Three silages made from perennial ryegrass (Lolium perenne) with formic acid as an additive were used. One was made from first-harvest grass in the spring and the others from regrowth grass cut from a single sward in either early autumn or late autumn. Expt I involved a comparison between the spring silage given alone or supplemented with barley (silage:barley, 4:I dry matter (DM) basis). Expt 2 involved a comparison between the early-cut and late-cut autumn silages.

In Expt I, supplementation of the silage with barley resulted in a non-significant (P > 0.05) reduction in the proportion of digestible energy (DE) and digestible organic matter digested in the rumen and an increase in the proportions digested in the small intestine. There were also pronounced effects of barley on ruminal cellulolysis and the proportion of digestible cellulose broken down in the rumen was reduced (P < 0.05) from 0.90 to 0.77. There was an increased passage of α-linked glucose polymers to the duodenum but even with the supplemented diet 0.91 of the dietary polymers were digested in the rumen. The molar proportion of propionic acid in the rumen tended to be reduced and there were increases in the proportions of butyric acid (P < 0.01) and acetic acid.

In Expt 2, the digestibility of organic matter, gross energy and cellulose in the early-cut silage was higher (P < 0.01) than in the late-cut silage but there were no significant (P < 0.05) differences between silages in the sites of digestion of these constituents. However, the molar proportion of acetic acid in the rumen was higher (P < 0.01) and the molar proportion of propionic acid was lower (P < 0.01) with the late-cut silage than with the early-cut silage.

The results are discussed in relation to the voluntary intake and utilization of high-digestibility silages.

1. Male WAG/Cpb inbred rats fed on rations with approximately 1–5rng copper/kg (deficient), 6.0 mg Cu/kg (adequate) and 25.0 mg Cu/kg (excess) were supplemented with varying amounts of molybdenum (0, 50, 150 and 500 mg/kg diet) and the effect on the Cu concentration of blood, plasma, liver and kidney, the caeruloplasmin activity of plasma and the Mo concentration of liver and kidney were studied.

2. Mo increased the Cu concentration of blood, plasma, liver and kidney and the Mo concentration of liver and kidney.

3. In the plasma of Mo-supplemented rats the presence of a Cu-containing fraction was demonstrated, the Cu of which did not react with dithiocarbamate and was not related to caeruloplasmin. The Cu in this fraction was not able to increase the caeruloplasmin activity in the plasma of Cu-deficient Mo-supplemented rats. The Cu concentration of the erythrocytes did not seem to have been increased by the Mo treatment.

4. When compared to Cu-adequate rats the effect of Mo on the Cu distribution was reduced both by Cu deficiency and Cu excess. This decreased effect of Mo was explained by reduced uptake or retention of MO in the body as observed in the liver and kidney.

1. Heat loss from three men and three women was measured in a direct calorimeter over 2 or 3 h periods and compared with that determined simultaneously from heat-flow meters attached to the skin surface at the waist. The comparisons were made at each of four ambient temperatures, 15, 20, 25 and 30°. Each subject wore a cotton boiler-suit and minimal underwear.

2. Oral temperatures and skin and clothing temperatures on both trunk and forearm were determined, thus enabling the subjects' internal and external insulation to be calculated.

3. Heat loss determined by the meters was lower than that determined by the calorimeter. The difference increased with increase in ambient temperature. ‘Meter’ heat loss decreased linearly as ambient temperature was raised.

4. It was concluded that heat-flow meters could provide a useful estimate of total heat loss when the evaporative component is low. The estimate might be improved if the subject is calibrated while wearing the meters in a calorimeter over several short periods. Heat-flow meters could therefore be of particular value in sedentary individuals, when the heart-rate method for estimating energy expenditure can be inappropriate.

1. An automated colorimetric method for determination of methionine using an iodoplatinate reagent is described. Methionine sulphoxide does not react under the chosen conditions.

2. The method may be used to distinguish between unoxidized and total methionine by doing one deter- mination without and one determination with previous reduction of a portion of the sample with titanium trichloride. Methionine sulphoxide is then obtained by difference.

3. The method has been used with protein concentrates, mainly fish meals, after hydrolysis with barium hydroxide. Interference from cysteine-cystine is eliminated by adding a small amount of cadmium acetate to the sample before hydrolysis.

4. Results obtained for total methionine and for methionine sulphoxide by independent methods show good agreement with results obtained with the iodoplatinate method.

The daily rates of synthesis of protein by the whole body and by the individual tissues were determined in two Hereford × Friesian heifers (236 kg and 263 kg live weight), and a dry Friesian cow (628 kg live weight).

The rate of whole-body protein synthesis (g protein/d) was estimated from the total flux through the blood of [3H]leucine and [3H]tyrosine following infusion at a constant rate for 8 h.

The fractional rates of protein synthesis (ks) in the tissues (g synthesized/d per g tissue protein) were obtained after slaughter of the animals at the end of the infusion period. The fractional rate of protein synthesis was calculated assuming that the specific radioactivity of free tyrosine in either the blood (to give ks, b) or the tissue homogenate (to give ks, h) defined closely the specific radioactivity of the amino acid precursor for protein synthesis. Total protein synthesis (As, b or As, h; g/d) in an individual tissue was calculated as the product of ks, b) (or ks, h) × protein content.

Based on the total leucine flux, i.e. without correction for oxidation, 1.6 kg protein were synthesized daily in the heifers; for the cow this value was 2.0 kg/d.

The sum of the daily total synthesis in the major tissues (muscle+bone+brain, gastrointestinal tract (GIT), liver, hide) gave values of 1.4–1.9 kg/d based on As, b, and 2.2–3.0 kg/d based on As, h.

The percentage contributions of the individual tissues to the total protein synthesis were similar in all three animals, for example based on As, h muscle was 12–16; carcass (muscle+bone+brain) 32–33; GIT 38–46; liver 7–8; skin 14–21%.

The contribution of muscle to total synthesis estimated from the leucine flux was 19–22%; this value is in agreement with those calculated on the same basis for other species.

The energy cost of protein synthesis was estimated to account for a maximum of 30% of heat production.

1. Pregnant guinea-pigs receiving a low dose of L-ascorbic acid (0.2 mg/100 g body-weight per d) developed a hypercholesterolaemia in the third trimester of pregnancy, whereas no change in serum cholesterol levels was observed in pregnant animals receiving a higher dose of the vitamin (2 mg/100 g body-weight per d).

2. Pregnancy in the group of guinea-pigs receiving the higher dose of L-ascorbic acid was associated with an increased biliary secretion of bile acids. No change was observed in the biliary secretion of bile acids in pregnant animals receiving the lower dose of L-ascorbic acid, but these animals secreted significantly more cholesterol.

3. Changes in the biliary secretion of cholesterol and bile acids in the pregnant guinea-pig according to L-ascorbic acid intake were reflected in the composition of the gall-bladder bile. Thus, the gall-bladder bile of guinea-pigs receiving the lower dose of L-ascorbic acid contained more cholesterol, while the gall-bladder bile of those animals receiving the higher dose of the vitamin had a higher content of bile acids.

4. The increased cholesterol content of the gall-bladder of pregnant guinea-pigs receiving the lower dose of L-ascorbic acid resulted in decreased bile acid:cholesterol and phospholipid: cholesterol values, conditions predisposing to cholelithiasis.

A simple procedure using 35S incorporation for the measurement of microbial protein in abomasal or duodenal digesta of ruminants was developed and tested.

Microbial protein synthesized in the rumen was labelled with 35S by intraruminal infusion of 35SO4 and a microbial fraction was isolated by differential centrifugation.

35S not bound by micro-organisms and present as inorganic 35S in whole digesta and in microbial fractions was oxidized to 35SO4 and the samples were brought into solution by acid-hydrolysis. 35SO4 was precipitated as Ba35SO4.

The proportion of microbial non-ammonia-nitrogen (NAN) in digesta NAN was determined as 35S:NAN (digesta) ÷ 35S:NAN (microbial).

In sheep offered grass nuts at maintenance level of feeding, 48% of NAN flowing through the abomasum was of microbial origin. NAN flow to the small intestine was estimated using chromic oxide as a marker and it was calculated that 49% of the grass N was degraded in the rumen.

1. Hepatic fatty acid synthesis, measured in vivo using 8H2O, was increased by a single dose of L-tryptophan (50 mg/kg body-weight) to both fed and fasted rats and by a supplement of tryptophan to the diet (2.5 g/kg diet for 7 d) when the rats were killed midway through the feeding period.

2. Additional dietary tryptophan was hypotriglyceridaemic in normal rats but exacerbated the hyper- triglyceridaemia in rats when lipoprotein clearance was impaired 24 h after an injection of Triton WR 1339 (Chromatography Services Co., Birkenhead, Cheshire).

3. The effects of tryptophan on hepatic fatty acid synthesis and the concentration of serum triglyceride were not directly related to the action of the amino acid on gluconeogenesis. A lack of correlation between inhibition of gluconeogenesis and enhancement of lipogenesis was confirmed using mercaptopicolinic acid, a specific inhibitor of phosphoenolpyruvate carboxykinase (EC 4.1.1.32).

4. DL-Tryptophan itself did not provide a significant contribution of substrate to the total rate of lipogenesis. Other possible explanations for the activity of tryptophan noted in the present experiments are discussed.

5. In conclusion, moderate intakes of tryptophan affect fatty acid and triglyceride metabolism under physiological conditions and it is proposed that the amino acid may be involved in the control of lipid metabolism in a variety of metabolic states.

1. Forty-eight male rats were fed sequentially for 14 d periods on diets containing different fibre contents.

2. One of the high-fibre diets was a commercial pelleted diet. The other was a low-fibre diet supplemented with 200 g wheat bran/kg.

3. At the end of each feeding period eight rats were killed. Liver microsomal cholesterol 7α-hydroxylase (EC 1.14.1.-) activity and bile acid content of small intestine and colon were determined.

4. The different diets did not significantly alter the total intestinal bile acids, but affected the distribution and qualitative pattern in the colon and small intestine.

5. On the high-fibre diets deoxycholate, and hyodeoxycholate tended to be increased.

6. On the low-fibre diets the α-, β- and ω-muricholic acids tended to be increased.

7. Liver microsomal cholesterol 7α-hydroxylase activity was lower in rats fed on the low-fibre and bran- supplemented low-fibre diets compared with that in rats fed on the commercial pelleted diet.

1. Dietary tryptophan was found to regulate the activities of tryptophan oxygenase (EC I. 13.I. 12)and quinolinate phosphoribosyltransferase (EC z.4. 2a) in liver.

2. With increasing tryptophan concentration in the diet containing 100 g protein/kg, tryptophan oxygenase activity increased while that of quinolinate phosphoribosyltransferase decreased. The response of these enzymes to dietary tryptophan at lower dietary protein level (25 g/kg) was not significant.

3. Liver nicotinate phosphoribosyltransferase (EC 2.4.2. 11)activity and kidney picolinate carboxylase (EC 4. I.I. 45) activity were unaltered with different tryptophan concentrations in the diet.

4. The response of various biochemical measurements was dependent on the tryptophan intake and the changes were marked below and above the requirement level of tryptophan.

5. It is suggested that the urinary excretion of quinolinic acid and N'-methylnicotinamide may be useful in assessing the tryptophan nutritional status and its requirement.

1. The effect of acute duodenal infusion of 99Mo-labelled sodium tetrathiomolybdate on caeruloplasmin (ferroxidase; EC 1.16.3.1) was examined in sheep. The diamine oxidase activity of this enzyme with respect to two substrates, p-phenylenediamine and o-dianisidine (both at their apparent Km concentrations) was inhibited.

2. The 99Mo appeared rapidly in plasma and was at first present predominantly in a trichloroacetic acid insoluble form; inhibition of oxidase activity was related to the levels of TCA-insoluble Mo. The behaviour of the copper prosthetic groups of caeruloplasmin was altered since some plasma Cu precipitated with the protein fraction after TCA treatment. The appearance of TCA insoluble Cu was related to the level of TCA-insoluble 99Mo and corresponded to the inhibition of diamine oxidase activity.

1. Seasonal changes in retinol-binding holoprotein (holoRBP) concentration in plasma of group of male and female Japanese quail (Coturnix coturnix japonica) were examined over 18 months.

2. In Expts 1 and 2 the birds were maintained under natural lighting conditions and in Expt 3 under artificial-light photoperiods corresponding to the changing daylength at 56° N latitude. All groups were at 18–20° and received Superlayers' (Rank Hovis McDougall) pellet diet.

3. The mean plasma holoRBP concentration in all groups changed in an annual cycle with minimal values in September–October and maximal values in February–April, when daylength or light photoperiod increased to more than 10 h.

4. The group mean values in the female cycle change 2- to 3-fold from 50–100 μg/ml in late summer to 220–280 μg/ml in the spring, whereas in the male the range is only 1.3–1.5 times, from 140–170 to 180–250 μg/ml.

5. In the female the rate of egg laying was maximal in April–May and lowest in November–December.

6. The spring increase in plasma holoRBP reflects the increased vitamin A requirement of birds for reproduction and it is presumably under hormonal control. The wider amplitude in the female cycle compared with the male probably arises from the additional demand for the transfer of vitamin A into the eggs and hence the need for a higher initial secretion rate from the female liver to meet it.

1. When weanling rats were fed on a diet containing 0.1 g/kg of the diet as polyunsaturated fatty acid, it was found that after 2 weeks the level of linoleate in the lymphocyte total lipids was 56 mg/ g total fatty acids, as compared with a level of 138 mg/ g in rats on a normal diet (P < 0.005). Similar levels were obtained from rats which had been fed for up to 16 weeks on the deficient diet, but in a group killed after 28 weeks on the diet the level was found to be only 20 mg/ g total fatty acids. The arachidonate level was found to be approximately 220 mg/ g total fatty acids, regardless of whether the rats were fed on a diet deficient in linoleate for up to 16 weeks or on a normal diet. In the group of rats killed after 28 weeks on the linoleate deficient diet, however, the arachidonate level was only 60 mg/ g total fatty acids.

2. Percentage values for total fatty acids are given for plasma, adipose tissue, and lymphocytes for rats on normal and experimental diets.

3. Scatter diagrams of the levels of linoleate v. arachidonate in the lymphocyte total fatty acids showed no correlation between the levels of the two acids (r 0.05), but similar plots of linoleate and oleate levels showed an inverse correlation (r – 0.68).