1. The changes in serum lipid and protein concentrations, and in carbohydrate tolerance were studied in eleven young male volunteers during a 3-week period of either nibbling or gorging a diet containing a high proportion of sucrose.

2. It was found that when gorging, the serum glyceride concentration rose early in the dietary period and reached a plateau, that the serum albumin concentration fell and that the glucose tolerance remained unchanged, although there was evidence for an increased rate of absorption of glucose.

3. On the nibbling regime, the serum glyceride concentration rose progressively over the 3-week period, the serum phospholipid concentration fell significantly and the serum albumin concentration fell but to a lesser degree than when gorging.

4. The glucose tolerance was improved when nibbling, and again there was evidence for an increased absorption of glucose.

5. An attempt is made to interrelate these findings.

1. The metabolism of tritium-labelled tocopherol was investigated in thirty-six wethers and forty-two ewes fed on hay known to produce nutritional muscular dystrophy (NMD).

2. In one experiment, the effect of selenium or vitamin E or both on the metabolism of tritium-labelled tocopherol was studied. No difference was found in the incorporation rate of radioactivity in tissues due to the addition of either of these components.

3. In a second experiment, significantly more radioactivity was found in the tissues of sheep dosed intramuscularly than of those dosed by stomach tube into the rumen. Excretion of radioactivity was rapid when labelled tocopherol was given into the rumen.

4. In a third experiment, the efficiency of vitamin E in preventing NMD in lambs was tested. Supplementation with vitamin E of the diet consisting of NMD-producing hay and given to ewes was ineffective as a prophylactic treatment. Direct administration of vitamin E to the lambs completely prevented the occurrence of NMD. Plasma vitamin E concentrations in the treated lambs were significantly higher than in untreated lambs at weekly sampling over a 4-month period regardless of whether the lambs were born from ewes treated with the vitamin or not.

1. Thirty-four cross-bred newborn lambs were used. A high-protein diet (25% protein calories) was supplemented daily with retinyl palmitate (range, 13.75–440 μg/kg live weight 24 h), or with β-carotene (range, 68.5–2200 μg/kg live weight 24 h) for 21 days.

2. Live-weight gain was not increased by supplementing the basal diet with either retinyl palmitate or β-carotene.

3. The relative weights of β-carotene and retinyl palmitate (expressed as retinol) that were required to produce equivalent concentrations of retinol in the serum varied from 5:1 to 25:1, and for the liver (retinal + retinyl esters, expressed as retinol) the ratio varied from 3:1 to 9:1.

1. The effect of riboflavine deficiency on in vivo incorporation of [2–14C]glycine into proteins of liver homogenates and its subcellular fractions has been studied on rats maintained on a 16 % protein diet.

2. Riboflavine deficiency did not seem to affect the in vivo incorporation of [2–14C]g1ycine into proteins of liver homogenates. But riboflavine deficiency caused increased and reduced invivo incorporation of [14C]amino acid into mitochondrial and microsomal proteins, respectively.There was no significant change in the in vivo incorporation of [14C]amino acid into proteins ofnuclear, ribosomal and soluble fractions in riboflavine deficiency.

3. Riboflavine deficiency caused enhanced and reduced proportions of liver mitochondrial and microsomal proteins, respectively.

4. The results are discussed as suggestive of enhanced and reduced protein synthesis in the mitochondrial and microsomal fractions, respectively, of riboflavine-deficient rats.

1. Eight groups of ten weanling rats were maintained for 60 d on diets containing calcium and phosphorus in the ratio 1:1 (w/w) at four different levels of mineral, namely 0.08, 0.12, 0.24 and 0.36% Ca, with and without the addition of ergocalciferol.

2. Provision of vitamin D increased final body-weight except at the highest level of mineral intake. Similarly, increasing the mineral intake increased final body-weight except at the highest level.

3. Vitamin D raised the serum Ca concentration at all levels of mineral intake but in the experiment as a whole had no significant effect on serum P concentration. Serum Ca concentration was significantly higher at the two higher levels of mineral intake than at the two lower levels. Increasing dietary mineral caused a progressive increase in serum P concentration, except at the highest level of intake.

4. In general, the addition of vitamin D to the diets had no effect on the fresh or dry weights of the humeri; there was an indication, however, that at the two lower levels of mineral intake, vitamin D reduced the fresh weight of bone. The addition of the vitamin caused a reduction in bone volume, and an increase in bone length, bone ash and the ratio of the weight of ash to the weight of organic matter in dry, fat-free bone. With increasing dietary mineral there was an increase in the value of all the bone measurements except bone volume, which was decreased.

5. The addition of vitamin D and increasing dietary mineral both caused an increase in tooth mass and ash content.

6. The ratios of tooth mass to bone mass, and tooth ash to bone ash were unaffected by vitamin D, but decreased with increasing mineral intake.

7. Histological examination of the bones showed that the animals receiving 0.08 % of Ca and P were markedly rachitic although the presence of vitamin D ameliorated the condition. When the dietary mineral intake was raised to 0.12% Ca and P the animals were less severely rachitic and in the presence of vitamin D the bones appeared normal.

8. The incisor teeth were abnormal at the two lower levels of mineral intake, but when vitamin D was provided, the histological appearance was improved. When the Ca and P level in the diet was 0.24%, the incisal dentine appeared normal but the apical predentine was slightlywider thannormal; addition of vitamin D produced teeth of normal appearance. The incisor teeth were normal in appearance in the remaining groups.

9. These results are compared with those obtained in two previous studies where the Ca to P ratios were 1:10 and 10:1 (Harrand & Hartles, 1968, 1969).

1. Thirty-five male cross-bred lambs at 3 d of age were given artificial milks with a protein- calorie concentration of 25 % and containing either lard, coconut fat, cottonseed oil, rapeseed oil, groundnut oil, soya-bean oil, safflower oil, tallow, maize oil or olive oil, homogenized with reconstituted skimmed cow's milk to provide 50 yo of the total energy of the diet. Two lambs were given a low-fat diet of reconstituted dried skim milk. All lambs were bottle-fed for 28 d.

2. The dietary fats and oils were highly digestible (97.2–99.5 %) with the exception of lard (89.1 %), rapeseed oil (61.9 %) and tallow (77.8 %). The indigestibility of these dietary fats was related to their content of stearic or erucic acids. The fatty acid patterns of the faecal fat were similar within each dietary group, but differed between diets.

3. Metabolic faecal fat excretion was 4.1 k0.5 g/100 g faecal dry matter. There was no similarity between the fatty acid composition of the metabolic faecal fat and that of the faecal lipids excreted by lambs given fat in their diet. The metabolic faecal fat made only a minor contribution to the total faecal lipids, so that the apparent and ‘ corrected’ digestibility coeffi-cients were very similar.

1. The action of vitamin D on the degree of mineralization of the bone tissue of rats given a diet containing adequate amounts of calcium and phosphorus for 8 weeks has been investigated by quantitative microradiography. The method is described.

2. There was a significant reduction in the growth of the vitamin D-deficient rats; the reduction was most marked in the females.

3. Serum analysis showed a reduction in Ca, but P was unchanged. However, the Ca × P product was considered to be high enough to permit normal mineralization.

4. The degree of mineralization of the cortical bone tissue increased significantly according to the distance from the epiphyseal plate. However, there were no significant differences between vitamin D-treated and vitamin D-deficient animals.

5. It is concluded that vitamin D deficiency in rats does not prevent the formation of a bone matrix which can attain a normal degree of mineralization.

1. Urinary excretions of creatinine (Cre) and hydroxyproline (OHPr) were measured in two groups of children: (a) 24 h collections in male and ‘spot’ samples in female marasmic infants throughout the course of treatment, and (b) ‘spot’ samples in underprivileged pre-school children at home. Results were related to certain somatic measurements and in some instances to some dietary factors.

2. Analysis of 24 h samples taken at intervals throughout 120 d of treatment showed a steady rise towards normal levels from very low initial values of OHPr. There was no corre-lation with age or body-weight on admission, nor of OHPr excretion through recovery with increase in height. Excretion of Cre also increased during recovery but the trend was more erratic. There was no relation to initial weight deficit or age but mean Cre excretion through recovery did correlate with rate of increase in weight. Values of Cre excretion at different stages of recovery expressed in terms of weight or height differed somewhat from those reported by others. The possible significance of these findings is discussed.

3. High correlations of the OHPr index according to Whitehead (1965) determined on 6 h and 24 h collections provided evidence for the representative nature of ‘spot’ samples.

4. Partial correlation analysis of body-weight and urine volume in relation to Cre excretion (mg/24 h) showed that the former (r = 0.719) had a greater influence than the latter (r= 0.485).

5. In a subgroup of eleven marasmic infants aged 3–5 months multiple linear regression analyses of OHPr and Cre excretion on somatic and dietary factors revealed no consistent correlations.

6. Periods of lowered OHPr and Cre excretion were frequent but in only half of the instances were they related to intercurrent infection.

7. A high correlation was found between changes in excretion of OHPr and of Cre throughout recovery.

8. An appraisal was made of the OHPr index according to Whitehead (1965). On the basis of the considerable influence that age was shown to have on this index during the preschool period an OHPr index (age-adjusted) was suggested for use.

9. The OHPr index (age-adjusted) determined on ‘spot’ samples from underprivileged preschool children at home and from marasmic infants during recovery was shown to be closely correlated with a modified ‘index of thriving’ based on somatic measurements.

10. The value of Cre and OHPr determinations in the study of severely malnourished children during recovery and in the detection of mild undernutrition is discussed in the light of these experimental results.

1. Two wethers fitted with permanent rumen cannulas were used to study the effect of two mineral supplements, Na2HPO4 and a 1:1 mixture of Na2CO3 and NaHCO3, on the buffering system in the rumen of sheep given a pelleted roughage-concentrate diet.

2. Measurements were made of rumen pH, buffering capacity value (β), total volatile fatty acids (VFA), CO2 and inorganic phosphorus concentrations as well as rumen cellulase activity.

3. The addition of either mineral supplement to the diet significantly (P < 0.001) increased the rumen pH values during the critical post-feeding period, there was a difference of only 0.5 pH unit between the minimum and maximum pH values.

4. Both mineral supplements significantly increased the concentrations of CO2 in the rumen fluid and rumen cellulase activity. They resulted in a general reduction in total VFA concentrations. It is suggested that this may possibly arise from increased absorption of VFA associated with increased CO2 tension in the rumen fluid.

5. The Na2HPO4 supplement significantly ( P < 0.001) increased the β values in the pH range 6–8, whereas the bicarbonate supplement contributed to raising the β values in the pH range 5–6.

6. The bicarbonate supplements raised cellulose digestibility from 39.7% for the control diet to 45.6% and the addition of Na2HPO4 further raised the digestibility to 51.1%. It would appear that low rumen pH impairs rumen cellulase activity and this could be offset by the addition of mineral supplements.

1. The fatty acid composition of the depot fats of thirty-six preruminant lambs was determined. Four lambs were slaughtered at 3 d of age, two lambs were fed on a low-fat diet for 28 d, and thirty lambs in groups of three were given ten different dietary fats in artifcial milk diets for 28 d.

2. The fatty acid patterns of the carcass fats were closely related to those of the dietary fats, and within-treatment variations were extremely low. Significant differences in fatty acid composition were observed between the skin, carcass, perinephric and subcutaneous lipids, irrespective of the diet given.

3. The carcass lipids of lambs given the low-fat diet were similar in their fatty acid composition to those of lambs aged 3 d, though the former lambs lost fat from the carcass during the experimental period.

1. S 24 perennial ryegrass was harvested at six stages of its growth from young leafy herbage to mature grass in which the seed had shed.

2. Two sheep were offered 1kg/d of each cut and two other sheep were offered 750 g/d of each cut of grass.

3. The contents of some possible precursors of the urinary aromatic acids excreted by sheep, namely, shikimic acid, quinic acid, chlorogenic acid, total o-dihydroxyphenolic compounds, lignin and crude protein were determined in each cut of grass.

4. A gas-liquid chromatographic method for the determination of the aromatic acids present in light petroleum extracts of urine was developed.

5. The urinary excretion of creatinine, diethyl ether-soluble acids, hippuric acid, total benzoic, phenylacetic and phenylpropionic acids, and the apparent digestibilities of nitrogen, lignin and dry matter were determined with each sheep offered each cut of grass.

6. The quantity of the various aromatic acid fractions excreted by sheep decreased as the maturity of the herbage increased and was directly proportional to the amount of food consumed.

7. No relationship was found between the intake of possible benzoic acid precursors and the urinary excretion of benzoic acid. With diets of young herbage, smaller amounts of benzoic acid were excreted in the urine than would be predicted from the intakes of the precursors studied, and with mature herbage greater amounts were excreted than would be predicted.

8. Possible reasons for these results are discussed, and the nature of additional precursors of urinary aromatic acids excreted by sheep given mature herbages are considered.

9. Urinary excretion of phenylacetic acid varied with diet in a manner which closely followed the intake of apparently digestible nitrogen. A highly significant (P < 0.001) exponential relationship was found between these two variables; it was log10 E = 0.05 N –0.63, where E is the urinary phenylacetic acid output (g/kg food) and N the intake of apparently digestible nitrogen (g/kg food).

1. Diets containing 1000 kcal/day with varying proportions of carbohydrate (CHO) were fed to four women with simple obesity. The patients were given, in various sequences and for 8 days in each instance, diets in which 3, 6, 12, 25 or 50% of the calories were supplied by sucrose.

2. No significant difference in the rate of weight loss was found when the diets of graded CHO content were fed and mean weight loss was 1.2 kg/week.

3. The high-CHO diets were antiketogenic; there was no daily relationship between urinary ketones and sodium. The 25 and 50% CHO diets had a nitrogen-sparing effect.

4. A 1000 kcal/day diet with about a third of the calories derived from CHO leads to a useful rate of weight loss and minimum changes in body chemistry. This finding may have implications in the long-term treatment of obesity.

1. Two experiments were carried out with sheep and cattle receiving high-concentrate rations to estimate the amount of digestion taking place in the rumino-reticulum and omasum. Two techniques were used for the collection of samples of abomasal contents. In the experiment with sheep, animals were slaughtered at different times after feeding and samples of digesta were collected. In the experiment with cattle, samples were collected through an abomasal fistula at 2 h intervals throughout the entire 24 h. Chromic oxide powder was incorporated into the ration.

2. Digestion of DM in the rumen estimated by the chromic oxide ratio ranged from 36 to –7%. Estimates based on the lignin ratio ranged from 57 to 68%. Estimates based on lignin as the marker were more consistent within experiments.

3. Starch digestion in the rumen based on the chromic oxide ratio ranged from 56 to 92% while estimates based on the lignin ratio ranged from 89 to 96%. The amount of starch digested, according to chromic oxide ratios, was up to 500 g more than estimated organic matter digested in sheep, and up to 2 kg more than organic matter digested in cattle, both impossible results. Estimates based on lignin were always less than estimated dry-matter digestion.

4. In view of the untenable results obtained by using chromic oxide powder mixed in the ration as an indigestible marker, while lignin in the same samples always yielded credible results, it appears that chromic oxide is not always a suitable marker for estimating rumen digestion from abomasal samples.

1. Seventy-two bull calves, comprising forty-eight Ayrshire and twelve each of the Friesian and Jersey breeds, were used in a randomized block experiment. They were reared from birth on liquid diets, offered in two feeds daily, at either restricted or ad lib. levels. The restricted level of feeding was such that sufficient diet was fed to allow for a weight gain of I kg/d, and the calves given this level of feeding were slaughtered at a weight 77 kg above the mean birth weight of the breed. The calves given the diets ad lib. were slaughtered at 22 % of mature cow weight of the breed.

2. Three milk substitutes, based on spray-dried skim-milk powder, spray-dried whey powder and margarine fat, were compared. Two of these were high-protein diets (26–29 % protein) designed to contain either 20 % fat (LFHP) or 30 yo fat (HFHP) and the other was a low-protein diet (19 % protein) designed to contain 30 yo fat (HFLP).

3. Age at slaughter was lowest for diet HFHP and highest for diet HFLP. Total dry-matter intake did not differ between treatments, but daily dry-matter intake was lower on diet HFLP. Relative weight gain did not differ between diets LFHP and HFHP but was much greater than that for diet HFLP. After adjustment for differences between treatments in mean daily dry-matter intake, relative weight gain tended to be highest for diet HFHP. No difference occurred between treatments in the incidence of diarrhoea and of a high rectal temperature (> 39.33°). However, mean rectal temperature was higher for calves given the HFHP diet than for those given the HFLP diet.

4. Digestibility and nitrogen and calcium balance trials were made on six of the replications of Ayrshire calves at 4 and 10 weeks of age. Dry-matter intake at 10 weeks of age was lower for calves given diet HFLP than for those given the other diets. Apparent digestibility of fat tended to be lower for the HFLP diet. True digestibility of protein did not differ significantly between treatments. Apparent digestibility of lactose was highest for the HFLP diet.

5. No difference occurred between the two high-protein diets (LFHP and HFHP) in N or Ca retention, but N and Ca retention by calves on the low-protein diet (HFLP) was markedly lower. Daily faecal N excretion was unaffected by treatment, but daily urinary N excretion was lower and the biological value of the protein was higher for diet HFLP than for diet LFHP, with the corresponding values for diet HFHP being intermediate between the two. N reten tion/100 g weight gain was lower on diet HFLP, lower at 4 weeks of age than at 10 weeks, and lower at the restricted than at the ad lib. level of feeding at 4 weeks of age. Metabolic faecal N and endogenous urinary N at 4 weeks of age were estimated as 0.192 g/100 g dry-matter intake and 192.9 mg/kg0.72 live weight respectively.

6. Haematological findings showed that the high-fat diets (HFHP and HFLP) resulted in a slower rate of decline in packed cell volume and haemoglobin content with age. The low protein diet (HFLP) resulted in a lower rate of increase with age in the percentage of lymphocytes. Diet HFHP resulted in a decline with age in the percentage of eosinophils compared to a marked rise with the other two treatments.

7. Carcass weight did not differ between treatments, but perirenal fat deposition was much higher for the calves given the high-fat diets (HFLP and HFHP).

8. It is concluded that dietary fat is not a readily available source of energy for increasing N retention in calves given large quantities of milk substitutes, based on milk products with added fat. Unless additional fat deposition in the carcass is required, no advantages in weight

1. Riboflavine given orally to sheep, calves, goats and ruminating kids gave rise, in milk and urine, to extra riboflavine accompanied by hydroxyethylflavine, by formylmethylflavine and by other as yet unidentified metabolites, but subcutaneous injection of riboflavine caused prolonged excretion of riboflavine in urine and milk unaccompanied by metabolites.

2. Placement of riboflavine by means of fistulas into the rumen, the abomasum or the caecum and abstraction of samples from the rumen or caecum showed that the rumen was the site of origin of the metabolites, thus accounting for the lapse of time of several hours between the ingestion of riboflavine and the appearance of hydroxyethylflavine in the urine and the absence of metabolites after subcutaneous injection of riboflavine.

3. Kids in which rumination had not yet become established could not produce metabolites from ingested riboflavine although, when fed milk containing the metabolites, they readily excreted them in their urine.

5. Incubation in vitro of kidney or liver tissue from cattle or goats with riboflavine did not give rise to metabolites, but these tissues could both reduce formylmethylflavine to hydroxyethylflavine in vitro.

6. Post-mortem examination of animals to which riboflavine had been fed showed the presence of metabolites only in gut contents, in the urinary bladder and in the bile. When injected, riboflavine reached the bile but no metabolites were produced.

7. Metabolites were found to occur naturally in the urine of ruminants in small amounts. Hydroxyethylflavine was readily demonstrable in the urine of the rabbit, but in the urine of the dog metabolites could not be found.

8. From these and earlier and later experiments the conclusion is drawn that riboflavine metabolites arise in the ruminant from the degradation of riboflavine by rumen bacteria.

1. A combination of balance and isotope techniques has been used to study calcium metabolism in ten sheep at different stages of pregnancy, and the results have been combined with earlier results obtained during lactation to show the variations in Ca metabolism which occur during the whole reproductive cycle.

2. Transfer of Ca to the foetuses during pregnancy and to the milk after parturition rose rapidly from the 65th day of gestation and reached a maximum at parturition or shortly afterwards.

3. Although the rate of absorption of Ca from the intestine increased steadily throughout pregnancy it was insufficient to meet the full requirements of late pregnancy and early lactation. During this period, the extra Ca was supplied by increased bone resorption.

4. The maternal Ca balance became negative during pregnancy, the net daily loss of Ca reaching a maximum in early lactation.

5. In late lactation the maternal Ca balance became positive enabling the animals to replenish their skeletal stores.

6. There was no marked change in the demands for Ca at parturition and the connexion between this observation and the pathogenesis of milk fever is discussed.

7. Rates of transfer of Ca to the foetus during pregnancy are compared with estimated values of other workers.

1. By feeding safflower-seed oil to rats deficient in the essential fatty acids it was found that major changes in the liver and serum triglycerides had occurred in 4 d although the fatty acid composition had not fully returned to normal.

2. Rats which had been on a saturated-fat diet for 18 weeks were given for 4 d, a diet supplemented with safflower-seed oil, methyl linolenate or ethyl arachidonate. Linoleic and linolenic acids failed to reduce the liver triglycerides but had some effect in raising the serum triglycerides to normal. Arachidonic acid reduced liver triglycerides but had no effect on serum lipids. There were marked changes in the fatty acid composition of the phospholipids but little change in the triglycerides.

3. There was good correlation between the concentrations of the phospholipids and the triglycerides in the serum. The concentration of serum phospholipids was positively correlated with the percentage of linoleic and arachidonic acids but negatively correlated with the percentage of palmitoleic, oleic and 5, 8, 11-eicosatrienoic acids.

4. In a further 4 d feeding experiment in which the lipoprotein fraction of very low density from the serum was measured, it was found that safflower-seed oil led to an increase but methyl arachidonate resulted in a decrease in the concentration of the lipids.

5. Extraction of the lipoprotein fraction of very low density from normal and deficient rats with n-heptane at – 18° indicated that phosphatidyl cholines containing stearic acid and either arachidonic or 5, 8, 1 1-eicosatrienoic acid were the most firmly bound.

6. It was concluded that linoleic acid and arachidonic acid had different and specific roles in lipid metabolism.

1. Twenty-four bull calves consisting of fifteen Friesians and nine Ayrshires in a randomized block experiment were reared from birth on liquid diets offered ad lib. in two feeds daily to a slaughter weight equivalent to 22 % of mature cow weight of the breed.

2. The three diets given after the calves had received 7 kg whole colostrum were (a) fresh liquid skim milk containing 0.1 % butterfat, (b) a ‘high-fat’ diet containing reconstituted spray-dried skim milk and 2.8 % margarine fat, and (c) the ‘high-fat’ diet for 14 d from birth followed by liquid skim milk. All calves received supplements of magnesium and iron, and vitamins A, D and E. Digestibility and balance trials were made on nine calves of each breed at both 4 and 10 weeks of age. Certain observations were made at slaughter.

3. Dry-matter and gross energy intakes of calves given the skim-milk diet were greater than for those given the ‘ high-fat ’ diet. Daily weight gain, efficiency of food conversion, incidence of a high rectal temperature ( > 39.33°), mean rectal temperature and faecal dry-matter content were greater for the calves given the ‘ high-fat ’ diet. Age to slaughter and incidence of diarrhoea were much greater for the calves given liquid skim milk.

4. Apparent digestibility of lactose and apparent absorption of ash and calcium were greater withthe ‘high-fat ’diet, but no difference occurred in apparent digestibility of dry matter or protein. Metabolic faecal fat excretion was estimated from the intercept of the relationship between apparently digested fat and fat intake for the calves given the liquid skim-milk diets; the values obtained ranged from 29 mg/kg live weight for Friesian calves at 10 weeks to 49.5 mg/kg for Ayrshire calves at 4 weeks. The true digestibility of the fat was estimated.

5. No difference in Ca or nitrogen retention occurred between diets, but urinary N excretion and N retention/100 g gain in weight were markedly higher and concentration of N in the urine was much lower for calves given the skim milk.

6. Perirenal fat deposition per unit of metabolic body size was 168 % greater for calves given the ‘ high-fat ’ diet. Kidney weight and skin weight were greater for the calves given the liquid skim-milk diet. The increased kidney weight was related to the very large urine output of the calves given skim milk.

7. In comparison with Ayrshire calves, Friesian calves were much less susceptible to the adverse effects of liquid skim milk, having a lower incidence of diarrhoea and faeces of a higher dry-matter content, but they did have a higher incidence of lung lesions. Friesian calves also had a higher relative growth rate, efficiency of feed conversion, mean body temperature, faecal pH, apparent absorption of Ca, retention of N and Ca per unit of metabolic body size and killing-out percentage, but lower skin weight per unit of metabolic body size. Perirenal fat per unit of metabolic body size did not differ between breeds.

1. The concentrations of volatile fatty acids (VFA) in the rumen and caecum were compared when sheep were given barley or dried grass. The molar proportions of VFA in the caecum resembled those in the rumen except that the proportions of isobutyric and isovaleric acids were higher in caecal than in rumen fluid indicating an extensive breakdown of protein during fermentation in the caecum.

2. The capacity for starch digestion in the large intestine was studied in two sheep receiving dried grass. Starch was infused into the caecum, the amount given increasing by daily increments of 20 g until 300 g daily were infused. Infused starch in excess of 138 g daily largely appeared in the faeces, indicating a limited but substantial capacity for starch fermentation in the large intestine. The infusion caused a marked increase in the molar proportion of butyric acid.

3. Determinations made with a single sheep showed that the infusion of starch into the caecum caused large changes in the microflora, and species similar to Butyrivibrio became prevalent. The viable count on a starch medium was increased by 83 % by starch infusion.

4. The infusions of starch increased the excretion of nitrogen in the faeces from 5.8 to 9.0 g daily. Using a fractionation procedure it was shown that when 100 g of starch were fermented in the large intestine the 'bacterial and endogenous debris' nitrogen increased by about 1.0 g. When starch was given orally to two sheep the increase in this fraction was about 0.4g nitrogen/100 g starch digested.

5. It is suggested that dietary factors that cause changes in the site of fermentation from the rumen to the caecum will render less microbial nitrogen available to the host animal per unit of carbohydrate fermented and decrease the apparent digestibility of nitrogen.

1. Copper deficiency was induced in growing rabbits and the effects of ascorbic acid supplementation were studied.

2. Signs of Cu deficiency, including reduced growth, achromotrichia and alopecia, anaemia, and gross alterations in the bones of the forelimbs, developed most rapidly in those animals fed ascorbic acid.

3. Microscopic lesions in ossification centres were seen only in bones of rabbits which hadm received the vitamin.

4. Calcium and phosphorus contents of ash from cortical bone were not changed.

5. Compared with the controls, the concentration of liver Cu decreased and that of iron increased (> 50%) in Cu-deficient animals.

6. Cytochrome oxidase activity was reduced in liver and heart in Cu-deficient animals; this effect was accentuated in heart preparations from animals fed ascorbic acid.