1. Pangola grass (Digitaria decumbens) was grown with or without sulphur fertilizer, cut at seven stages of growth, dried and given to sheep with or without a supplement of 0.6 g S as sodium sulphate/d. Voluntary intake and digestibility of dry matter (dm) and retention time in the reticulo-rumen, of various components of the grasses were determined.

2. Grass grown on the S-fertilized plots had a mean S content of 1.57 g/kg dm compared with 1.03 g/kg dm for the control but there was no difference in the level of other elements. S fertilizer increased the level of acid-detergent fibre and lignin.

3. In the absence of a S supplement, fertilizer S increased voluntary intake by 10.5%, dm digestibility by 0.008 and reduced the period food dm was retained in the reticulo-rumen by 18.5%. Fertilizer S had no effect on rumen pH or volatile fatty acid concentration in rumen fluid, but decreased the molar proportions of propionic and butyric acids and increased those of acetic, isobutyric, isovaleric and caproic acids.

4. Supplementary S had little effect on the voluntary intake and dm digestibility of the S-fertilized grass but increased the voluntary intake and dm digestibility of the control grass by 22% and 0.036 respectively (P < 0.01). Thus the voluntary intake and dm digestibility of S-fertilized grass was lower than that of the control grass when the determinations were made with sheep supplemented with S.

5. It was concluded that S fertilizer increased nutritive value by overcoming a simple S deficiency in the diet when diets contained less than 1.7 to 1.8 g S/kg dm but this benefit was offset by a decrease in the content of digestible neutral-detergent solubles and an increase in the lignin content of the food.

1. A study was made of protein utilization in rats given a variety of low-protein diets containing (g/kg) egg albumin 18, casein 49, gluten 50, or mixtures of either maize protein and gelatine 58, or casein and gelatin 37, each with supplemental methionine. The diets were limiting in leucine, tryptophan or lysine, or in both tryptophan and the sulphur-containing amino acids.

2. Values obtained for net protein utilization (npu) at these low levels of nitrogen intake were markedly higher than the amino acid score calculated for the different test proteins, except with casein for which the two values were similar. The npu values agreed more closely with chemical score values based on the content of S-amino acids or isoleucine in the dietary protein.

1. Rats were given diets containing different fats (200 g/kg) from weaning to 8 months of age. The fats were sunflower-seed oil (SFO), lard (L) and an equal mixture of sunflower-seed oil and lard (mixed-fat diet; MF). A control group was given the basal diet unsupplemented with fat. Energy intake and body-weight of individual animals were recorded weekly.

2. Three animals from each dietary group were killed after 5, 13, 17 and 29 weeks on the experimental diets. At slaughter epididymal fat pads were excised, weighed and the number and size of fat cells in the pad was determined.

3. There were no significant differences between the energy intake in the whole experimental feeding period for rats given the different fat diets. However, when energy intakes were examined on a monthly basis animals given MF had a significantly higher energy intake in the first 2 months of feeding than those animals given SFO. In the third month of feeding (when animals were over 12 weeks old) the group given L had a significantly higher intake than the group given SFO.

4. Body-weight, epididymal-fat-pad weight, cell size and cell number did not differ significantly between the ‘fat-fed’ animals at any individual slaughter period. Analysis of pooled values from the four slaughter periods revealed that animals given MF had significantly more fat cells than those given SFO.

5. We conclude that the nature of the dietary fat has no effect on the cellularity of developing adipose tissue but that the number of fat cells formed is sensitive to energy intake before 12 weeks of age in the rat.

1. Heavy-breed (HB) chicks differed from light-breed (LB) ones in their propensity to be overfed. Whereas in the LB chicks the amount by which they could be overfed reached 70 % more than the food consumed daily by the ad lib.-fed chicks, in the HB chicks the maximal excess was only 13 %.

2. Overfeeding caused a slight but statistically significant increase in the linear growth rate (shank length) of the LB chicks, with an opposite effect in the HB chicks.

3. Overfeeding increased the weight of the crop, proventriculus, small intestine, pancreas, liver and adipose tissue but had no such effect on the heart, cerebrum or cerebellum.

4. Overfeeding had no effect on the specific activities of the pancreatic digestive enzymes, liver xanthine dehydrogenase, or tryptophan oxygenase (EC 1.13.1.12). The increase in the total activities was due entirely to organ hypertrophy.

5. Obesity induced in young chicks had no residual effects on the adult LB chicks, but reduced the linear growth of the adult HB chicks.

6. An explanation for the difference between breeds in response to overfeeding at an early age is discussed.

1. The influence of replacing 10 % of the urea nitrogen in a purified diet with casein, maize gluten or white fish meal on the efficiency of conversion of dietary-N into microbial N was examined using sheep equipped with rumen fistulas and duodenal re-entrant cannulas.

2. Total nitrogen (TN), non-ammonia nitrogen (NAN) and amino acid nitrogen (AAN) flowing to the proximal duodenum were significantly higher (P < 0.05) when maize gluten was added to the diet, and this appeared to be due to an increased efficiency of microbial protein production.

3. Pepsin secretion was not significantly different between treatments and the daily amount of pepsin N flowing to the proximal duodenum was very small (40–53 mg). The peak of pepsin activity in duodenal digesta was reached 6–8 h after feeding.

4. The possible practical implications of the results are discussed.

1. The fatty acid compositions of muscle and brain phospholipids of foetal calves, neonatal lambs, deer calves and piglets, and mature cattle, sheep, deer and pigs were determined. The cattle, sheep and deer had previously grazed ryegrass–clover pastures, and the pigs had been given rations based on barley. Two steers and four sheep had been given protected polyunsaturated lipid-protein supplements.

2. In muscle phospholipids the values for triene:tetraene were 1.5 for neonatal lambs and 0.3 for foetal calves. Levels of linoleic acid were low compared with those in older animals but levels of the fatty acids 22:5ω3 and 22:6ω3 were comparatively high. For arachidonic acid there was little difference between young and mature animals.

3. In muscle phospholipids of neonatal piglets and deer calves values for triene:tetraene were low. The piglet also had a low value for 22:5ω3:22:6ω3 compared with those in deer, calves or lambs. This ratio showed a proportionately greater increase with maturity in the pig than in cattle and sheep. Whilst the neonatal deer had higher linoleic acid levels than the other young ruminants, the fatty acid composition of muscle phospholipids of mature deer was rather similar to that in other ruminants.

4. Phospholipids of brain showed little difference in fatty acid composition between foetuses or neonates and the mature animals. There was higher 22:4ω6 content in the adult ruminant with even higher levels in sheep given protected polyunsaturated fat. Linoleic acid was barely evident in any animal. The 22:6ω3 content was as high in the foetal or neonatal ruminant brain as in the adult, and higher than in the piglet. The fatty acid composition of brain phospholipids of young deer was similar to that in other ruminants.

5. In other tissue phospholipids in foetal or neonatal ruminants and piglets there were high levels of 22:6ω3 in liver and low levels in lung. The neonatal animals, in particular, had high palmitic acid levels in lung. Hearts of young ruminants contained high levels of 20:5ω3 and C16-aldehyde derived from plasmalogens. Piglet heart contained higher linoleic acid and arachidonic acid, possibly due to increased entry of linoleic acid across the placenta from the sow.

1. Information on the fatty acid composition of tissues of foetal calves, neonatal lambs, deer and piglets reported by Payne (1978) has been quantified by the use of an internal standard during analysis, to give concentrations of total polyunsaturated fatty acids (PUFA) derived from linoleic acid (ω6) and linolenic acid (ω3) expressed on a per kg tissue basis. The total concentration of both acids (ω6+ω3) was similar in all tissues examined except brain. Because muscle, the main constituent of the soft tissues of young animals, contains about 40–50 % of the total body content of these acids, it is considered that muscle concentrations are a reflection of total body status of these acids.

2. Concentrations in muscle of both ω6 derivatives and total PUFA were significantly lower in the neonatal lamb and foetal calf than in the mature animal whereas in pigs and deer the concentrations in the young animal were similar to those in the mature animal. Concentrations of ω6 derivatives and total PUFA in lambs were significantly lower than those in calves; the presence of ω3 derivatives reduced the level of significance for total PUFA. Again, total PUFA content did not differ significantly between the piglet and the young ruminants.

3. There was a substantial placental transfer, with apparently a preferential transfer of ω3 derivatives.

4. In brain the levels of ω3 acids were as high in the foetal and neonatal animals as in mature animals. The levels of ω6 acids were lower in young animals.

5. Calculations of ω6 intake from milk showed that the total deficit of ω6 could be made up within a few days.

6. It was concluded that the extent of deficiency of ω6 in young ruminants raised in a grazing situation, as in New Zealand, is marginal and any feeding to overcome this is unlikely to be of any benefit.

1. Effects of incorporating 30 g leucine/kg into diets on quinolinate phosphoribosyl transferase (QPRT; EC 2.4.2.19) activity and leucine aminotransferase (EC 2.6.1.6) activity were studied in groups of rats receiving 5, 30 and 60 μg of pyridoxine/10 g diet.

2. The results indicated that 30 g leucine/kg diet significantly reduced the QPRT activity when the diets provided 5 μg pyridoxine/10 g and that the effect was only marginal when the diet included 30 μg pyridoxine/ 10 g. The inhibitory effect was completely absent when the diet provided higher amounts of pyridoxine (60 μg/10g).

3. These results suggest that additional amounts of pyridoxine are necessary to counteract the effects of excess of leucine in the diet.

4. Leucine aminotransferase activity was increased in rats given diets containing higher amounts of pyridoxine; supplementary leucine also increased the enzyme activity.

1. [35S]sulphate was used to obtain quantitative estimates of the transfer of sulphur between the blood, rumen and postruminal tract of four sheep given brome grass (Bromus inermis) pellets or lucerne (Medicago sativa) pellets at the rate of 33 or 66 g/h. Sodium sulphate (0–4 g S/d) was infused into the rumen or abomasum of sheep given brome grass during four periods of 19 d and was not infused into the sheep during a subsequent period in which lucerne was given. The flow of sulphide, sulphate, microbial S and non-microbial organic S from the abomasum was estimated using 103Ru and 51Cr.

2. The concentration of inorganic sulphate in serum was increased to maximum values of 35–46 mg S/l by infusion of sulphate into the rumen or abomasum. The rate of irreversible loss of serum sulphate and rumen sulphide was positively related to the amount of sulphate infused.

3. Reabsorption of sulphate by the kidney reached a maximum of 0.69–1.1 mmol sulphate/l glomerular filtrate.

4. The transfer of sulphate from blood to the rumen was related to the concentration of inorganic sulphate in serum, attaining maximum values of 133 (±13) mg S/d for sheep given brome grass plus sulphate, and 127–159 mg S/d for sheep given lucerne.

5. Bacteria derived 0.52–0.67 of organic S from rumen sulphide in sheep given brome grass, and approximately 0.45 of bacterial organic S was derived from sulphide for sheep given lucerne. Protozoa derived approximately 0.90 of organic S from bacteria.

6. It was estimated that endogenous organic S contributed 300–340 mg S/d to the rumen, and that 0.24–0.45 of S digested in the rumen was derived from endogenous sources.

1. Responses of hepatic glucose-6-phosphate dehydrogenase (EC 1.1.1.49; G6PD), malic enzyme (EC 1.1.1.40; ME), acetyl-CoA carboxylase (EC 6.4.1.2; ACAC), and fatty acid synthetase (FAS) were studied in male Wistar rats after a period of starvation and refeeding of diets containing 400 g glucose, or raw or cooked starches as the source of carbohydrate/kg. Starches fed included maize, potato, wheat, rice, and tapioca.

2. When compared to the responses of rats given the glucose-containing diet, rats given raw maize- or rice-starch-containing diets had a significantly lower ME response, and rats given raw potato starch had significantly lower responses of G6PD, ME, ACAC, and FAS. The enzyme responses of rats given cooked starches were similar to those of glucose-fed rats, except that rats given cooked wheat starch had significantly lower G6PD and ME responses than did glucose-fed rats.

3. When the enzyme responses to refeeding of the same starch source in either raw or cooked form were compared, it was found that (a) the FAS response was significantly higher to cooked than to raw maize starch, (b) the G6PD and ACAC responses were significantly higher to cooked than to raw tapioca starch, (c) the G6PD, ME, ACAC, and FAS responses were significantly higher to cooked than to raw potato starch.

4. The results suggest that reported differences in the lipogenic enzyme responses between simple sugars and starch may in some instances be magnified because of the use of uncooked starches in experimental diets.

1. The renewal of the intestinal mucosal epithelium has been investigated in germ-free and conventional chicks given a practical chick diet and a low- and high-fibre diet, using tritiated thymidine to label the nuclei of mucosal cells undergoing division.

2. Villus height, crypt depth and number of mitoses in the crypt were generally, although not always significantly, greater for conventional chicks than for germ-free chicks at all sites investigated in the intestine, and all became progressively lower from the upper intestine to the lower intestine.

3. There was a linear relationship between the height of the radioactively labelled mucosal cells on the villus and the period after injection, and the rates of epithelial cell migration were higher for conventional than for germ-free chicks, the relative differences being greater in the lower intestine than the upper intestine.

4. The inclusion of wheat bran as a source of dietary fibre had no effect on the rate of epithelial renewal, either in germ-free or conventional birds.

1. Groups of three colostomized germ-free (GF) and conventional (CV) chickens aged 4 months were maintained for successive periods of 8 d on a diet containing 200 g casein/kg without and with sodium bicarbonate at the rate of 20 mmol/d and a nitrogen-free diet without and with NaHCO3 at 9 mmol/d. Urine and faeces were collected during the last 3 d of each period.

2. Total N, uric acid- and ammonia-N were determined in urine and total N in faeces. Amino acids were measured in hydrolysates of faeces collected during the periods when no NaHCO3 was included in the diets.

3. The CV birds excreted more N on the casein diets but less on the N-free diets than did their GF counterparts, the differences being mainly shown in the urine.

4. On both diets hydrolysates of the faeces of CV birds contained smaller amounts of amino acids. On the N-free diet the proportions (g/160 g N) of serine, proline and threonine were reduced, suggesting some conservation of endogenous N by micro-organisms, and the proportions of histidine, alanine, lysine and methionine increased, possibly through microbial synthesis; on the casein diet, proportions of most amino acids were less, probably because bacterial deamination had occurred.

5. Urinary excretion of total N, uric acid and ammonia was much greater on the casein than on the N-free diets. Inclusion of NaHCO3 caused a sharp fall in urinary ammonia on both diets and in both environments.

6. It was concluded that the level of dietary protein and the regulation of acid-base balance have more effect than microbial activity on the urinary ammonia excretion.

1. Six closely shorn sheep were given brome grass (Bromus inermis) pellets at the rate of 59 or 98 g dry matter (dm)/h and maintained at ambient temperatures of 2–5° and 22–25° for 35 d. Measurements of digestion, rate of passage of digesta, and nitrogen transformations were made during the last 13 d of temperature exposure.

2. Cold exposure at the lower level of intake reduced the apparent digestibility of dm and organic matter (om) approximately 0.055 units. Apparent digestibility of dm and om was further decreased approximately 0.03 units with the higher level of food intake in the cold. Apparent N digestibility was significantly depressed from 0.62 to 0.59–0.60 for sheep exposed to cold at both levels of intake.

3. Exposure of sheep to cold resulted in a decrease in the turnover time of the particulate marker, 103Ru, from 19 h to 10.12 h in the rumen, a decrease in rumen volume, and a significant increase in dm and om which escaped digestion in the stomach. Volatile fatty acid and methane production in the rumen were highly correlated with the amount of om digested in the stomach. Methane production in the rumen comprised 0.81 of total production in warm sheep, and 0.68–0.74 of total production in cold-exposed sheep.

4. More om and non-ammonia-N were apparently digested in the intestines of sheep exposed to cold than in warm sheep at the same food intake, but the apparent digestibilities in the intestines of dm, om and non-ammonia-N leaving the abomasum did not change significantly between treatments. The retention time of 103Ru in the intestines was 17.18 h in sheep given 59 g dm food/h at both exposure temperatures, but was reduced to 12 h for cold-exposed sheep given 98 g dm/h. Methane production in the postruminal tract was increased at the higher food intake, but there was no difference between warm and cold-exposed sheep at the same food intake.

5. The rate of irreversible loss of plasma urea and rumen ammonia was measured by infusion of [15N]urea and [15N]ammonium chloride. Exposure to cold reduced the irreversible loss of plasma urea from 0.85 to 0.75–0.77 g N/g N intake, and the irreversible loss of rumen ammonia from 0.66 to 0.57–0.61 g N/g N intake. The transfer of plasma urea-N to the rumen ammonia pool was significantly greater (9.5 g N/d) in the cold-exposed sheep than the value (7.3 g N/d) in warm sheep.

6. The efficiency of microbial synthesis in the rumen was increased in cold-exposed sheep, and was related to the amount of N recycled through the rumen ammonia pool from intraruminal sources. The effect of dilution rate and fermentation patterns on efficiency of microbial synthesis is discussed.

1. Plant foods, especially green leafy vegetables, are the cheapest and richest source of calcium in developing countries and are recommended in balanced diets. Hence it was worth while obtaining further information about the availability of Ca from these commonly-consumed green leaves.

2. The green leafy vegetable belonging to Amaranthus spp. was taken as a suitable experimental model because it is not only commonly-consumed, but is also rich in Ca and oxalates. In the first experiment, each of the eight adult male subjects was given a basal diet containing negligible Ca, a milk diet and an ‘Amaranthus’ diet, both containing the same amount of Ca. These diets were given on 3 consecutive days and the urinary Ca excreted in a 6 h period after the test diet was considered an approximate index of Ca absorbed in that period. The second experiment was designed to study the influence of Amaranthus spp. on the availability of milk Ca. Each of the ten adult male subjects were given a basal diet, a milk diet and a diet containing the same amount of milk with Amaranthus spp. added to it. Urinary Ca excreted in a period of 6 h was estimated.

3. While availability of Ca from milk was good, that from Amaranthus leaves was low. The ingestion of Amaranthus leaves together with milk adversely affected the absorption of milk Ca.

4. In view of these findings, recommendation of green leaves as a regular source of Ca to the vulnerable section of the Indian Community should be considered with caution. Since green leaves are a main source of other nutrients, especially β-carotene, their consumption cannot be discouraged and hence leaves low in oxalates should be recommended.

1. Male Wistar rats were given isoenergetic, semi-synthetic diets deficient in thiamin, riboflavin, pyrid-oxine or all the B-vitamins.

2. In rats given these deficient diets the ‘sleeping time’ induced with pentobarbital (PB) and the ‘paralysis time’ with zoxazolamine (Zz) were prolonged.

3. The tolerance effect against both drugs was nearly independent of the levels of B-vitamins in the diets.

4. In preparations from vitamin-B deficient animals the activities of the following hepatic microsomal enzymes were reduced: the aliphatic hydroxylase of PB, the aromatic hydroxylases of aniline (EC 1.14.14.1) and of Zz, the N-demethylase of aminopyrine, the UDP glucuronyltransferase (EC 2.4.1.17) of p-nitrophenol. The reactions most influenced were those of ‘type-1’ substrates, particularly those involving the hydroxylases.

5. The effects observed were caused mainly by deficiency of riboflavin and to a lesser extent of thiamin or pyridoxine.

1. Leucocyte ascorbic acid concentrations have been measured in 1147 females during early pregnancy and in smaller numbers of women before conception, throughout pregnancy and at 6 months post partum.

2. The leucocyte concentration in the 1st trimester was found to be affected by season, social class and smoking. Selecting individuals by extremes of social class, season and smoking produced two small populations with almost separate ascorbic acid distributions and mean concentrations of 21.7 and 45.1 μg/108 leucocytes.

3. Early pregnancy had little effect on leucocyte ascorbic acid concentrations but values decreased in the second trimester. However, this was associated with a leucocytosis so that the total leucocyte ascorbic acid content of blood was unchanged.

4. Low ascorbic acid concentrations during the 1st trimester were not associated with subsequent spontaneous abortions, still-births or neonatal deaths, but there was an increased frequency of low values in women who gave birth to infants smaller than 3250 g.

5. The adequacy of ascorbic acid reserves in early pregnancy is discussed.

1. Chicks, 3-d-old, of a heavy breed (HB) and a light breed (LB) were overfed for 18 d. The activities of acetyl-CoA carboxylase (EC 6.4.1.2; CBX), fatty acid synthetase (FAS), ATP citrate lyase (EC 4.1.3.8; CCE), NADP-malate dehydrogenase (decarboxylating) (EC 1.1.1.40; ME), 6-glucose-6-phosphate dehydrogenase (EC 1.1.1.49; G6PDH) and phosphogluconate dehydrogenase (EC 1.1.1.44; 6PGDH) were determined in abdominal adipose tissue (AT) and liver samples of overfed and ad lib.-fed chicks. Size and fat content of liver and adipose tissue were also determined in order to evaluate the extent of obesity.

2. On ad lib.-feeding HB chicks consumed more food, gained more weight and deposited more fat than the corresponding LB chicks. Their lipogenic enzymes were more active than in the LB chicks in both adipose tissue and liver. The increase in food consumption (%) that could be achieved by overfeeding was three times greater in the LB chicks than in the HB chicks.

3. Overfeeding increased the weight and fat content of liver and AT in both breeds. The specific activities of CBX, FAS, CCE and ME in liver and AT increased in the LB chicks only and the total activities of liver and AT enzymes increased much more in the LB chicks than in the HB chicks in which the increase was derived mainly from tissue enlargement.

4. The activity of the pentose cycle dehydrogenases was very low in liver, but in AT about one third of the NADPH generating capacity could be accounted for by these dehydrogenases.

5. The results show that lipogenic enzymes of chicks respond to an increased substrate flux. It is suggested that the enlarged liver, the higher participation of AT in lipogenesis and the uninterrupted supply of cropstored excess food enable the chick to accommodate the increased amounts of substrate with only moderate enzymic adaptation.

1. The effects were examined of two approximately isoenergetic diets differing widely in saturated fat content on the levels of serum cholesterol and triglycerides of nomads and non-nomads in eastern Niger. Each person was also examined for clinical and electrocardiographic evidence of heart disease.

2. No significant differences could be found between serum cholesterol and triglyceride levels of 297 Anagamba nomad men consuming 73 % energy as fat and 303 Kanouri sedentary men consuming 9 % energy as fat.

3. Rheumatic heart disease was common in nomads and four possible cases of ischaemic heart disease were found in sedentary men only.

1. Three sheep, each fitted with a ruminal cannula and duodenal re-entrant cannulas were given three isonitrogenous, isoenergetic diets in a Latin-Square design. Each diet contained (/kg) approximately 400 g N as white fish meal, soya-bean meal or urea and approximately 600 g dry matter (dm) was barley grain. The diets were fed continuously and supplied about 28 g N/d.

2. Total duodenal digesta was collected manually for 72 h and the proportions of microbial N in that digesta were simultaneously estimated for all sheep using RNA, radioactive sulphur (35S), diaminopimelic acid (DAPA) and aminoethylphosphonic acid (AEPA) as markers.

3. Three of the estimation methods showed that the variable source of dietary N had the greatest (RNA P < 0.05, 35S P < 0.005, DAPA P < 0.1) effect on the proportions of microbial N in duodenal digesta, though differences between sheep accounted for some variation.

4. These methods also ranked the diets in the order: urea > soya-bean meal > fish meal with respect to the proportions of digesta N that were microbial in origin; the respective mean values for these diets with the different markers were: RNA 0.98, 0.70, 0.56; 35S 0.92, 0.64, 0.54; DAPA 0.80, 0.47, 0.42.

5. AEPA was found to be present in substantial quantities not only in isolated rumen protozoa, but also in dietary and bacterial material; an observation that invalidated its further use as a protozoal marker.

6. Calculations using values obtained from the 35S procedure showed that the proportions of dietary N degraded within the rumen were 0.38, 0.43 and 0.89 for the white fish meal, soya-bean meal and barley respectively.

7. The marker methods are compared and their advantages and disadvantages (real and apparent) are discussed. It is concluded that where microbial N estimates of a more general and comparative nature are required, the use of RNA as a marker is probably adequate. Where information for more exacting purposes is required, the use of 35S appears to be more appropriate.