Body fat content of seven lean women (body mass index (BMI) 20.6 (sd1.8) kg/m2) and seven overweight women (BMI 31.1 (sd 3.3) kg/m2) was estimated by six different methods: underwater weighing (UWW), body-water dilution (BWD), whole-body counting (40K), skinfold thickness (SFT), bio-electrical impedance (BEI) and magnetic resonance imaging (MRI). Using UWW as the reference method, the differences between percentage fat by each other method and the percentage fat by UWW were calculated for each subject. The mean difference was lowest for SFT and highest for BWD. MRI showed the lowest variability in individual results, and 40K the highest. 40K and BWD methods used in combination gave better agreement with UWW results than either 40K or BWD methods alone. There was a weak negative correlation between the difference from the UWW results and percentage fat in the SFT measurements, but not in the BWD, 40K, BEI or MRI measurements, suggesting that for these methods the assumptions involved produced no greater inaccuracy in the overweight women than in the lean women. In all subjects the BEI offered little improvement over the traditional SFT measurements. The agreement between MRI and UWW estimates in both lean and overweight women suggests that MRI may be a satisfactory substitute for the more established methods of body fat estimation in adult women.

In 1229 subjects, 521 males and 708 females, with a wide range in body mass index (BMI; 13.9–40.9 kg/m2), and an age range of 7–83 years, body composition was determined by densitometry and anthropometry. The relationship between densitometrically-determined body fat percentage (BF%) and BMI, taking age and sex (males =1, females = 0) into account, was analysed. For children aged 15 years and younger, the relationship differed from that in adults, due to the height-related increase in BMI in children. In children the BF% could be predicted by the formula BF% = 1.51xBMI–0.70xage–3.6xsex+1.4 (R2 0.38, SE of estimate (see) 4.4% BF%). In adults the prediction formula was: BF% = 1.20xBMI+0.23xage−10.8xsex–5.4 (R2 0.79, see = 4.1% BF%). Internal and external cross-validation of the prediction formulas showed that they gave valid estimates of body fat in males and females at all ages. In obese subjects however, the prediction formulas slightly overestimated the BF%. The prediction error is comparable to the prediction error obtained with other methods of estimating BF%, such as skinfold thickness measurements or bioelectrical impedance.

The responses of dwarf mice to dietary administration of clenbuterol (3 mg/kg diet), daily injections of growth hormone (15 μg/mouse per d) or both treatments combined were investigated and their actions, and any interactions, on whole-body growth, composition and protein metabolism, and muscle, liver and heart growth and protein metabolism, were studied at days 0, 4 and 8 of treatment. Growth hormone, with or without clenbuterol, induced an increase in body-weight growth and tail length growth; clenbuterol alone did not affect body-weight or tail length. Both growth hormone and clenbuterol reduced the percentage of whole-body fat and increased the protein:fat ratio. They also increased protein synthesis rates of whole body and muscle, although the magnitude of the increase was greater in response to growth hormone than to clenbuterol. Clenbuterol specifically induced growth of muscle, with a decrease in liver protein content, whereas growth hormone exhibited more general anabolic effects on tissue protein. Previous reports have suggested that effects of clenbuterol on skeletal muscle are mediated, at least in part, via decreased rates of protein degradation; we could find little evidence of any decrease in whole-body or tissue protein degradation and anabolic effects were largely due to increases in protein synthesis rates. However, small increases in muscle protein degradation rate were observed in response to growth hormone. Growth hormone induced a progressive increase in serum insulin-like growth factor-1 concentration, whereas there was no change with clenbuterol administration. Anabolic effects on whole-body and skeletal muscle protein metabolism, therefore, appear to be initially via independent mechanisms but are finally mediated by a common response (increased protein synthesis) in dwarf mice.

Failure to thrive (FTT) in infants with congenital heart disease (CHD) can be attributed to their low energy intakes and high resting energy expenditures. Energy intake, energy expenditure and growth were studied in infants with CHD on normal formula feeds and then on feeds supplemented with glucose polymer to see whether supplementation improved energy retention and growth. Mean gross energy intakes increased by 31.7% on high-energy feeding and mean weight gain improved from 1.3 g/kg per d on control to 5.8 g/kg per d on high-energy feeding. Resting oxygen consumption (νo2 ml/kg per min) was not significantly different on the two feeding regimens, although respiratory quotient rose on high-energy feeding reflecting the increased carbohydrate intake. Estimated energy costs of growth on high-energy feeding fell within the previously described range for normal infants. It is recommended that infants with CHD known to be associated with FTT are fed on high-energy diets from the time of diagnosis in order to optimize growth.

Total daily energy expenditure (TEE) by the doubly-labelled (2H218O) water method and basal metabolic rate (BMR) by indirect calorimetry were measured in thirty-two healthy free-living adults in Northern Ireland. Habitual physical activity patterns in occupational and discretionary activities were assessed by interview questionnaire. Expressed as a multiple of BMR the TEE values for the sixteen males (1.88 (sd 0.28), range 1.44–2.57) and sixteen females (1.77 (sd 0.16), range 1.50–2.06) were compatible with current Department of Health and Social Security (DHSS; 1979) and Food and Agriculture Organization/World Health Organization/United Nations University (FAO/WHO/UNU; 1985) estimates of energy requirements. The results suggest that discretionary physical activity is now emerging as an equally important determinant of energy expenditure in the UK as the occupational classifications currently used as the basis of DHSS (1979) and FAO/WHO/UNU (1985) recommendations for energy requirements. Therefore, realistically achievable inputs of recreational exercise can have a significant impact in counteracting low levels of energy expenditure which are associated with modern lifestyles and are implicated as a risk factor for coronary heart disease and obesity.

The aim of the present experiment was to determine the relationship between placental and fetal weight after placental growth had been retarded by maternal undernutrition. Placental weight and fetal weight were measured in single-lamb-bearing ewes which were well-fed throughout pregnancy, or severely undernourished between the 30th and 96th day of pregnancy. Placental transfer of calcium and whole-body metabolism of both glucose and Ca were measured during late pregnancy. The change in fleece-adjusted live weight between the 30th and 96th day of pregnancy was 99 (se 9.8) and – 146 (se 9.6) g/d for the well-fed and undernourished ewes respectively. The condition score of well-fed ewes did not significantly change between the 96th (2.9 (se 0.08)) and 140th (3.0 (se 0.13)) day of pregnancy, while it increased from 1.6 (se 0.15) to 2.3 (se 0.11) for the previously undernourished group. Undernutrition caused an increase (P < 0.01) in placental weight measured on the 96th (21%) and 140th (30%) day of pregnancy. In contrast fetal growth was not significantly affected by maternal undernutrition. While the voluntary dry matter intakes (g/d) of previously undernourished ewes after the 97th day of pregnancy were higher than for their well-fed counterparts, there was no significant difference between whole-body glucose or Ca metabolism, or the placental transfer of Ca measured during late pregnancy. This experiment confirms earlier reports of an increase in placental weight as a result of maternal undernutrition during mid-pregnancy; but the factors causing and the functional significance of this response have not been identified. Contrary to earlier proposals, placental weight per se did not limit fetal growth during late pregnancy. It is hypothesized that a combination of factors originating from maternal, placental and fetal sources act together to regulate growth of the fetus.

Gastric intubation was adopted to examine the effect of continuous nutrient supply on digestive development of the pig during the immediate post-weaning period. The 14 d-weaned animals were slaughtered at 3, 5 and 7 d post-weaning (3W, 5W and 7W respectively) and the suckled animals were slaughtered at 14 and 22 d of age (14SR and 22SR respectively). The weight of the pancreas (g/kg body-weight) was significantly greater (P < 0.05) in the 5W and 7W groups, as was the weight of large intestine (g/kg) in all weaned groups (P < 0.01) compared with sow-reared pigs. The stomach weight (g/kg) tended to be greater in the weaned groups. Weaning, in conjunction with a continuous nutrient supply, did not significantly alter the time-related changes in the weight of the small intestine (SI) or the SI mucosa, although both variables tended to be lowest in the 3W group. However, there was a 20% reduction in the protein content of the mucosa within the first 3 d post-weaning (P < 0.01) which persisted during the 7 d experimental period. Lactase, (β-galactosidase; EC 3.2.1.23) activity (μmol/g protein and mol/d) of the 7W group was reduced to approximately 40% of the 22SR value. Hence, continuous nutrient supply may have delayed, but did not prevent, the loss of lactase activity at weaning. The activity of sucrase (sucrose-α-glucosidase; EC 3.2.1.48) was significantly higher in 22SR compared with 14SR animals. Sucrase activity in weaned pigs was intermediate to the values for sow-reared pigs whereas maltase (α-glucosidase; EC 3.2.1.20) and glucoamylase (glucan 1, 4-α-glucosidase; EC 3.2.1.3) were significantly increased in relation to their sow-reared counterparts. Continuous nutrient supply did not prevent the reduction in villous height and the crypt hypertrophy associated with weaning. The results of the present study suggest that there may be some degree of interaction between nutrient intake and gut development during the immediate post-weaning period but that there is also a component of the adaptive response which is independent of nutrient intake. They confirm the rapid substrate induction of the brush-border glucoamylases and indicate the importance of considering total as well as specific enzyme activity for satisfactory interpretation of changes in digestive function.

Gastric intubation was adopted as a means of comparing the effect of two feeding levels, continuous nutrient supply (C) and restricted nutrient supply (R), on the digestive development of pigs weaned at 14 d of age, during the first 5 d post-weaning. The absolute weights of the stomach and the pancreas were significantly greater (P < 0.001) in C compared with R pigs. The effect was not significant for pancreas weight when expressed per kg body-weight but was significant (P < 0.05) for stomach weight. The weights of the small intestine (SI), SI mucosa and total mucosal protein were significantly higher (P < 0.001) in C pigs but protein content per g mucosa was similar in the C and R groups. There was no significant effect of treatment on the activity of lactase (β-glucosidase; EC 3.2.1.23) or sucrase (sucrose-α-glucosidase; EC 3.2.1.48) irrespective of the basis of comparison used. The specific activity (μmol/min per g protein) of maltase (α-glucosidase; EC 3.2.1.20) and of glucoamylase (glucan-1,4-α-glucosidase; EC 3.2.1.3) were similar in C and R groups but activities of maltase (μmol/g mucosa) (P < 0.05), and maltase and glucoamylase (mol/d) (P < 0.01) were significantly higher in C pigs. Villous height and crypt depth were significantly greater in C pigs (P < 0.001 and P < 0.05 respectively). Enteroglucagon was significantly (P < 0.05) higher in C compared with R pigs. Xylose absorption and the digestibility of energy were not affected by treatment. Digestibility of dry matter, organic matter, crude protein (nitrogen x 6.25) and carbohydrate were significantly higher (P < 0.001, P < 0.01, P < 0.05 and P < 0.001 respectively) in R pigs compared with C pigs but the differences were small, ranging from 1.3 to 2.5 %. These results demonstrate that (1) nutrient intake in the weaned pig affects the anatomy, morphology and function of the gut, (2) there is considerable ‘spare capacity’ for digestion of cereal-based diets even in pigs weaned at 14 d of age, (3) measurements in vitro of digestive function are of limited value unless supported by information in vivo on absorption/digestibility.

Diets containing vegetable tannins, predominantly hydrolysable gallotannins, at levels of 13.5, 25 and 50 g/kg were fed to growing broiler cockerels to examine their effect on enzymes in the pancreas, the intestinal lumen and the intestinal mucosa. Pancreas weight per unit live weight showed a significant (P < 0.05) increase with increasing level of dietary tannin while that of the liver remained unaffected. Trypsin (EC 3.4.21.4) and α-amylase (EC 3.2.1.1) activities in the pancreas of birds fed at the highest level of tannins were more than double those from birds fed on a tannin-free control diet. In the intestinal lumen inhibition of trypsin activity increased with increasing level of dietary tannin; α-amylase activity was inhibited at intermediate tannin levels but was restored at the highest level. Dipeptidase (EC 3.4.13.11) and sucrose α-glucosidase (disaccharidase) (EC 3.2.1.48) in the intestinal mucosa were both inhibited by tannins. Growth of the birds and digestibility of nitrogen were adversely affected by the tannin-containing diets.

The effects of polysaccharides and tannins present in the hulls of field beans (Vicia faba L.) on the digestion of amino acids, starch and lipid were studied in poultry. A control diet without hulls and the same diet substituted with 400 g hulls/kg diet from three different varieties of beans were fed to 3-week-old chicks for 4 d. Digestibility coefficients for amino acids, starch and lipid were calculated from measurements made of these nutrients in the diets and the freeze-dried excreta with the aid of titanium dioxide as a marker. Activities of trypsin (EC 3.4.21.4), α-amylase (EC 3.2.1.1), and lipase (EC 3.1.1.3) in digesta removed from the upper jejunum, sucrase (EC 3.2.1.48) in the gut mucosa from the upper jejunum, and α-amylase and lipase in the pancreas were measured. The hulls were analysed for their polysaccharide and tannin contents. Results showed that the hulls were mostly carbohydrate in composition, with cellulose the predominant polysaccharide. Tannins present in the hulls of two coloured-flowering varieties (Brunette and Minica) were of the condensed type. The diet with tannin-free hulls (white-flowering variety Medes) lowered slightly the digestion of amino acids, starch and lipid compared with the control diet. This effect was believed to be due to inhibition of digestive enzymes, possibly through their adsorption onto the hulls. Diets with tannin-rich hulls (varieties Brunette and Minica) caused a large reduction in the digestion of amino acids, starch and lipid compared with the control diet mainly due to inactivation of digestive enzymes by the formation of tannin–enzyme complexes in the digestive tract. Enzyme activities could be partially restored by the addition of polyvinylpyrrolidone to the digesta. Tannins inactivated trypsin the most, α-amylase to a lesser extent and lipase the least and as a consequence lowered the digestion of amino acids the most, starch to a lesser extent and lipid the least. Tannins did not induce an increased pancreatic production of digestive enzymes, nor did they affect activity of jejunum mucosal sucrase. Condensed tannins from Brunette and Minica hulls were partially extractable in methanol alone, but required acidic methanol for fuller extraction. The vanillin: anthocyanidin ratio suggested that tannins were polymerized to the same degree in the Brunette and Minica varieties, both in the methanol and acidic methanol extracts. Hulls from the variety Minica contained a greater amount of methanol-extractable tannins, the quantity of remaining tannins that required acidic methanol for extraction being the same for both varieties.

The present work was undertaken to study the gastrointestinal effects of wheat and oat dietary fibre (DF) using 40–50 kg pigs cannulated in the terminal ileum. The variables studied were: chemical characteristics of the DF, ileal and faecal digestibility of nutrients and bulking properties of polysaccharides and other major constituents. The wheat products studied included refined wheat flour and wheat fractions rich in the following botanical components: aleurone, pericarp/testa and bran. The oat products used were rolled oats and oat bran. The products varied considerably in DF content (g/kg dry matter) and composition; non-starch polysaccharides (NSP) and Klason lignin content ranged from 34 and 1 g/kg respectively in wheat flour, to 465 and 92 g/kg in pericarp/testa. The main NSPs in the wheat were arabinoxylans (AX) (64–69%) and cellulose (15–31%) and in oats mixed linked β(1 → 3; 1 → 4)-D-glucans (β-glucans; 46–63%) and AX (28–32%). The lowest content of soluble NSP was found in the lignified wheat fractions (bran and pericarp/testa) and the highest in oat bran. Eight diets were produced using the wheat and oat products and studied in two series of experiments using wheat flour as the DF-depleted control. The diets in Expt 1 were based on wheat flour and three iso-DF enriched diets prepared by adding DF from the fractions rich in wheat aleurone, pericarp/testa or bran. In Expt 2, oat bran was added to wheat flour to achieve the same DF intake level as in Expt 1. This series also included diets based on rolled oats and rolled oats plus oat bran. Starch was almost completely digested in the small intestine (0.97–1.00). However, there was a tendency to a slightly lower digestibility of oat starch compared with wheat starch. The recovery of wheat NSP in ileal digesta was 82–104 % compared with 64–66% for oats. The low recovery of NSP in oat diets was primarily due to the low recovery of β-glucans (25–36%). In the large intestine NSP and starch residues were extensively degraded. For the DF-depleted control diets or diets based on oats, 8–17% NSP survived breakdown while in the diets enriched with aleurone, pericarp/testa or bran fractions, NSP recovery was 33, 50 and 38 % respectively. Fermentative breakdown of carbohydrates in the large intestine was estimated to contribute between 10 and 24 % of the energy for maintenance. Energy derived from the inflow of organic acids from the ileum contributed an additional 1–4% of maintenance energy. In wheat endosperm, AX were broken down to a greater extent than cellulose, while the breakdown of AX in pericarp/testa was similar to that of cellulose. This difference in NSP breakdown can be explained by structural differences in the two types of cell walls. The breakdown of oat AX was lower than that of wheat flour. Wheat DF increased faecal bulk primarily by virtue of its physical presence and its water-holding capacity, while the oat DF stimulated faecal output through an increase in microbial biomass (Bach Knudsen et al. 1991). The result was a higher excretion of protein and fat. The higher fat excretion with the oat diets was probably due to a higher bile acid excretion caused by the more extensive fermentation of carbohydrates and the lower lumen pH.

The present work was undertaken to study the microbial activity in various segments of the gastrointestinal (GI) tract of pigs as influenced by the source and level of wheat and oat dietary fibre (DF). Eight experimental diets were prepared from wheat and oat fractions and studied in a series of two experiments using wheat flour as the DF-depleted control. The diets in Expt 1 were based on wheat flour and three iso-DF enriched diets comprising fractions rich in wheat aleurone, pericarp/testa or bran. In Expt 2, oat bran was added to wheat flour to achieve the same DF intake level as in Expt 1. This series included further diets based on rolled oats and rolled oats plus oat bran. The eight diets were given to thirty-two ileal-cannulated pigs, with sixteen pigs in each experiment. After a total period of 34 d (Expt 1) and 42 d (Expt 2), the pigs were slaughtered 4 h post-feeding and samples taken for adenine nucleotides (adenosine 5'-triphosphate (ATP); adenylate energy charge (AEC)), organic acids (lactic acid (LA); short chain fatty acids (SCFA)) and pH at twelve sites of the GI tract. The microbial activity as measured by the ATP concentration was low in the stomach and the cranial two-thirds of the small intestine, but tended to increase in the distal third. In the caecum a sharp rise in microbial activity was observed; the highest level was found for the diet providing most fermentable substrates. In all the diets but the rolled oats+oat bran diets, microbial activity showed a descending pattern as the digesta moved through the colon. In the large intestine source and level of residues had a marked influence on microbial activity. LA was the chief organic acid in the stomach and small intestine (10–40 mmol/l) while LA relative to SCFA was a minor component in the caecum and colon (10–20 mmol/l). The contribution of SCFA to total organic acids was reciprocal to LA, i. e. low in the stomach and small intestine (<20 mmol/l) and high in the caecum and colon. In the large intestine the concentration of SCFA decreased from 100–140 mmol/l in the caecum and proximal colon to 40–80 mmol/l in the distal colon. The acetic: propionic acid ratio increased from the caecum to the distal colon. With the diets based on oat alone (rolled oats; rolled oats+oat bran) the increase was less significant. DF addition and oats in particular increased the butyric acid molar ratio, from 0.06–0.08 for the wheat flour diet to 0.10–0.12 for the diet based on rolled oats+oat bran. For the same two diets the proportion of isobutyric and isovaleric acids increased more rapidly with the wheat-flour diet compared with the rolled oats+oat bran diet.

The effect of dietary fibre and starch content on digestibility, microfaunal population and caecal function was investigated in a subterranean mole-rat, Heterocephalus glaber (Rodentia). Mole-rats were fed on a diet of either sweet potato (neutral-detergent fibre (NDF) 65 g/kg dry matter (DM), starch 638 g/kg DM) or carrot (NDF 157 g/kg DM, starch 258.7 g/kg DM) for 4 weeks. Daily intake and faecal output were monitored. Thereafter caecal microfaunal population, density and function were assessed using light and scanning electron microscopy and by measuring both gas and short chain fatty acid (SCFA) production. A 2.4-fold increase in fibre and 2.5-fold decrease in starch content resulted in a decrease in caecal DM content (390 g/kg). A concomitant dramatic decline (by 93%) in ciliate protozoa with a corresponding 2-fold increase in bacteria also accompanied this change in diet. Fermentative efficiency as indicated by gas production was 2.6 times greater on a carrot diet than on sweet potato. Microbial fermentation resulted in higher SCFA concentrations on the carrot diet, with a 42 % reduction in SCFA concentration on the sweet potato diet. Here, SCFA contributed 5.1 % of daily energy expenditure and this increased 5.0-fold on the carrot diet. Caecal micro-organism function, therefore, played an important role in the nutritional physiology of these naked mole-rats, and enabled maximum utilization of the food substrate.

The digestion by pigs of non-starch polysaccharides (NSP) in wheat and raw peas (Pisum sativum) fed in mixed diets was measured. In the four experimental diets, wheat was included at a constant 500 g/kg whilst peas contributed 0–300 g/kg and these were the only dietary sources of NSP. Separate estimates of digestibility for wheat and peas were obtained by using a multiple linear regression technique which also tested the possibility that the presence of peas might influence the digestibility of wheat NSP. There was little evidence of the latter and it was found that the digestibility of peas NSP (0.84) was considerably greater than that of wheat (0.65). The non-cellulosic polysaccharides (NCP) had twofold greater digestibilities than had cellulose for both foods with essentially all the peas NCP being digested. Faecal α-diaminopimelic acid concentration increased with feeding of peas, suggesting stimulation of bacterial biomass production in the large intestine using the readily fermented peas NSP. All three major volatile fatty acids produced by large intestinal fermentation were detected in jugular blood and increased significantly with increasing peas inclusion rate in the diet.

An evaluation was made into the usefulness of ferrous fumarate as an iron fortificant for an experimental chocolate drink powder targetted to children and adolescents. Organoleptically ferrous fumarate was acceptable when the chocolate drink powder was reconstituted in milk or water that was heated to < 80°. Unacceptable colour changes occurred, however, when boiling milk or water were used. In human Fe absorption studies when the Fe compounds were added to the chocolate drink immediately before consumption, ferrous fumarate was 3.31 % absorbed compared with 2.82% for ferrous sulphate and 2.11 % for ferric pyrophosphate. When the Fe compounds were processed during the manufacture of the chocolate drink powder, the absorption of ferrous fumarate was 5.27 %, ferrous sulphate 2.62 % and ferric pyrophosphate 0.55 %. Ascorbic acid had little or no effect on the absorption of ferrous fumarate. It is concluded that food processing can influence the relative absorption of fortification Fe and that, if not reconstituted with boiling milk or water, ferrous fumarate could be a useful compound for the fortification of chocolate drink powders.

Brewer's yeast was grown on a defined medium containing tracer 51Cr with or without added chromium. The two batches of yeast contained 10 μg/g (high-Cr) or 80 ng/g (low-Cr). Extracts were prepared and fractionated. A third batch of yeast (third batch) was grown with added Cr, and fractionated. Rats were reared on either rat cubes (normal diet) or on a low-Cr diet (low-Cr), or on rat cubes with added cholestyramine (cholestyramine diet). Preparations of rat liver, both cell-free and intact hepatocytes, incorporated acetate-carbon into fatty acids and cholesterol. These processes were inhibited by a yeast fraction containing small, neutral, water-soluble compounds. The degree of inhibition was the same whether the liver came from normal rats or rats fed on the low-Cr diet. Similarly the inhibitory effect was found with identical amounts of extracts from low- or high-Cr yeasts. Therefore, Cr compounds do not appear to account for the inhibitory effects of brewer's yeast. Use of other substrates indicated that the site of inhibition of sterol synthesis was apparently between acetyl-CoA and mevalonate. One inhibitory substance was isolated from yeast and was found to be nicotinamide riboside. This may have been produced from NAD(P) during the preparation of yeast extracts, and it may be produced from dietary yeast supplements during digestion in vivo. Nicotinamide riboside may be partly responsible for the reported effects of yeast supplements on plasma lipids in humans.

The purpose of the present study was to evaluate the contribution of various substrates to glucose synthesis in isolated sheep hepatocytes, and more specifically to quantify the contribution of propionate to gluconeogenesis. Liver cells from fed sheep have a very high capacity for propionate utilization and conversion into glucose. The glucogenicity of lactate or amino acids was very low in hepatocytes from fed sheep, but was significantly increased in hepatocytes from starved animals. Amino acids such as alanine or glutamine were characterized by a substantial utilization towards ureogenesis, whereas their conversion to glucose was very low. Propionate utilization and conversion into glucose was inhibited by butyrate, ammonia and especially ethanol (by up to 80%). Ethanol promoted a striking accumulation of intracellular malate in hepatocytes incubated with propionate (reaching 14.9 μmol/g cell) and led to a depletion of phosphoenolpyruvate; ethanol inhibition could be counteracted by pyruvate. Propionate and butyrate enhanced ureogenesis from ammonia in ruminant liver cells but their effects were not additive. Propionate also elicited a marked increase in cellular concentrations of phosphoserine and serine, particularly in the presence of ammonia; such effects could influence phospholipid metabolism in the liver. These findings emphasize the contribution of propionate, compared with the other glucogenic substrates, to glucose synthesis in ruminants and point to the possibilities of modulation of the glucogenicity of propionate by various substrates which may be present in portal blood.