1. Rat dams given a diet containing 100 g maize oil/kg for approximately 2 weeks before mating and during the first 14 d of gestation, were given the same diet or one containing 100 g hydrogenated coconut oil/kg (essential fatty acid (EFA)-deficient) in place of maize oil until parturition. After parturition the dams were given the same diets and all progeny were weaned to the maize oil diet at 21 d of age. Brain N-acetylneurammic acid (NeuNAc) content as well as neuraminidase (sialidase; (EC 3.2.1.18)) and cytidine monophosphate N-acetylneuraminic acid synthetase (CMP-NeuNAc synthetase) activities were measured at days, 7, 14, 21 and 168 in the progeny. Y-maze learning was measured at 168 d.

2. Brain weight was independent of dietary fat at all ages.

3. Lack of EFA in the maternal diet during gestation and lactation depressed ganglioside and glycoprotein NeuNAc levels and the activities of sialidase and CMP-NeuNAc synthetase.

4. Maternal dietary deprivation of EFA irreversibly impaired learning behaviour of the progeny. A relationship exists between early exposure to EFA deficiency and learning potential of the progeny.

1. This study investigated the subcellular localization of injected N-acetylneuraminic acid (NeuNAc) in brain. Forty pregnant rats were distributed into four groups. Two groups were given a 200 g casein/kg diel and the other two groups a 100 g casein/kg diet throughout gestation. One group from each of the low- and high-protein groups were given their respective diets for the first 11 d of lactation. On day 12 of lactation, 2·5 μCi [14]NeuNAc/kg body-weight were injected intraperitoneally into their pups. After 1 h the pups were killed, their brains removed and subjected to subcellular fractionation. On day 16 of lactation the other two groups were similarly treated.

2. In all groups of animals 80% of the [14C]NeuNAc incorporated into the brains was found in the synaptosomalfraction and the remainder distributed among the other subcellular fractions in proportion to their total NeuNA ccontent.

3. These results suggest that NeuNAc exerts its effects on behaviour via the synaptic membrane.

1. Male Wistar rats were meal-fed for at least 10d a control semi-synthetic diet containing no guar gum, or one of three similar test diets containing 3, 10 or 20 g dry guar gum/kg.

2. Rats were killed 6 h after feeding, and contents of stomach, small and large intestine were collected separately. The apparent viscosities of stomach and smalt intestine contents from animals fed on diets containing 10 and 20 g guar gum/kg were increased relative to control animals, but large intestine contents were unchanged

3. In the second part of this study, male Wistar rats were anaesthetized and two consecutive lengths of jejunum were perfused, initially with Ringer only (control) or Ringer plus 5 or 6g guar gum/1 (test). Following this pre-perfusion, both segments were perfused with Ringer containing glucose (10 mM), [3H]glucose and [14C]inulin, and the rate of glucose absorption was determined

4. The rate of glucose absorption was decreased relative to control values in segments pre-perfused with both 5 and 6g guar gum/I solution, but this reduction was significant only in the instance of the 6g/l solution (P< 0.001)

5. These results provide evidence to support previous assumptions that ingestion of guar gum will increase the apparent viscosity of the contents of the stomach and small intestine. We propose that a possible mechanism by which guar reduces post-prandial glycaemia is a reduction of glucose absorption from the smali intestine, resulting from an increase in viscosity of the contents

1. Water-holding capacity (WHC) of dietary fibre is usually considered as the amount of water held but the manner in which water is held by the fibre matrix may be more relevant in understanding the role of fibre in nutrition.

2. A method used to determine WHC under physiological conditions has been adapted to determine how strongly water is held by fibre. Solutions of compounds, such as polyethylene glycol, of known osmotic potential are used to generate a suction pressure across a dialysis membrane containing a fibre sample. The WHC at each suction pressure can then be determined.

3. The method can be applied to water-soluble and water-insoluble sources of fibre. Fibre sources studied included potato fibre concentrate, bran and gum arabic.

4. Results are comparable to other similar systems of WHC measurement for gels and suggest that vegetable fibre has water-holding properties more akin to a true gel than bran. Bran has very poor water-holding properties.

5. Differences in WHC between fibre sources are more apparent if WHC is considered as fibre concentration (g fibre/g water).

6. Differences in the water-holding properties could be important in determining fibre activity in the gut.

1. Erythrocytes (RBC) from control and marginally riboflavin-deficient subjects were fractionated into nine fractions using a discrete density gradient.

2. Glutathione reductase (NAD(P)H: glutathione oxidoreductase; EC 1.6.4.2) activity and aspartate aminotransferase (EC 2.6.1.1) activity (with and without the appropriate co-enzymes) reduced glutathione, methaemoglobin, sulphaemoglobin and oxyhaemoglobin and susceptibility to peroxide were measured in RBC in the different fractions.

3. Glutathione reductase and aspartate aminotransferase activities and concentrations of reduced glutathione and oxyhaemoglobin all declined with age, while melhaemoglobin, sulphaemoglobin and susceptibility to peroxide increased with age.

4. The only significant differences noted in the RBC from marginally-riboflavin-deficient subjects by comparison with controls, were lower glutathione reductase activities and higher concentrations of methaemoglobin.

5. The role of riboflavin in those sytems controlling RBC integrity is discussed.

1. Bread alone and supplemented with guar gum at three levels (50, 100 and 150 g/kg) was given to eleven non-diabetic subjects, and blood glucose and serum insulin were determined preprandialy, and at 30 min and 60 min after commencement of the meal. The satiating effect, up to 120 min, of the guar bread and its acceptability to the same group of normal volunteers was also studied.

2. No significant differences in blood glucose were observed between control and guar breads at 30 min and 60 min, apart from 100 g guar/kg bread at 30 min (P < 0·05). A significant difference in serum insulin was indicated between: control and 50 (P < 0·02) and 150 (P < 0·02) guar/kg breads at 30 min; control and 50 (P < 0·05), 100 (P < 0·001) and 150 (P < 0·05) guar/ke breads at 60 min.

3. There were no significant differences in the satiety scores for control and guar breads. Significant increases in satiety attributed to 150 g guar/kg bread were found when compared to: 50 g guar/kg bread immediately after eating (P < 0·05), 100 g guar/kg bread at 60 min (P < 0·02) and 50 and 100 g guar/kg breads at 120min (both P < 0·05).

4. There was a positive correlation between hedonic score and relative replacement of guar (r 0·62, P < 0·001, n 44) and from the regression line it was found that 50 and 100 g guar/kg breads produced hedonic scores close to a neutral response of 5, whereas 150 g guar/kg bread at a predictive score of 6·3 appeared to be unacceptable to our subjects.

5. Guar bread at the 100 g/kg level (59 g guar/kg bread) reduced the serum insulin by 48% at 60 min and is found to be an acceptable food product at this level of incorporation. However, more information is required to demonstrate the possible satiating potential of guar bread.

1. Rats were deprived of food for periods of from 0 to 40 h and then given 203Pb, 203Hg. 59Fe, 64Cu. 64Zn or 45Ca by stomach tube. The absorption and retention of these metals in tissues was measured 1 h and 2 d after dosing.

2. After 16–24 h of food deprivation between two and ten times more metal was retained than after 0–12 h.

3. The effects of length of fast on metal uptake by the intestinal mucosa were greatest in the duodenum.

4. Lactale production by duodenal mucosa was halved after 12 h of food deprivation but galactose absorption was little changed after a 40 h fast.

1. Eight insulin-dependent and eight insulin-independent diabetic patients and twenty-eight non-diabetic essential hypertensive patients were given a high-fibre, high-unrefined carbohydrate and low-fat diet for 3 months duration.

2. The effects of this dietary regimen on the patients' fasting blood glucose, hypoglycaemic therapy and weight was observed.

3. Fasting lipid profiles were obtained before and after 3 months on the dietary regimen, and total serum lipids and lipoprotein fractions were analysed.

4. The insulin-dependent and insulin-independent diabetic patients showed a reduction in hypoglycaemic therapy, with no significant change in fasting blood glucose. The insulin-independent and non-diabetic groups both showed significant weight loss.

5. The three groups of patients showed a significant reduction in cardiovascular risk factors with either an elevation of high-density lipoprotein (HDL)-cholesterol or a fall in low-density lipoprotein (LDL)-cholesterol and a reduction in the total cholesterol: HDL-cholesterol value.

1. A study was carried out to determine the effects of varying the level of energy intake on nitrogen balance in preschool children receiving the safe requirement level of protein, determined in an earlier study.

2. Seven preschool children received four energy levels, i.e. 293, 334, 376 and 418kJ/kg body-weight at the safe level of protein intake of 1·75 g/kg body-weight and N balance determined.

3. The N balance decreased with a decrease in energy intake. However, the N balance was positive at all levels of energy intake studied.

4. Results indicated that at a protein intake of 1·75 g/kg body-weight the minimum level of energy intake for a retention of 40 mg N/kg body-weight in these children was found to be 326·2±45·5 (mean ± SD) kJ/kg body-weight. Below this energy intake the safe level of protein intake became inadequate.

1. Three series of nitrogen balance experiments were performed with growing rats to test the effect of type and level of protein, fibre and starch on N excretion patterns. The design involved eighteen treatments in a 3×3×2 factorial experiment with five rats per dietary treatment. The eighteen treatments resulted from a combination of three protein treatments, three fibre treatments and two starch treatments. Protein treatments consisted of onelevel (15 g N/kg DM) of casein fortified with methionine, a protein of high digestibility, and two levels (15 and 20 g N/kg DM) of autoclaved brown beans (Phaseolus vulgaris), a protein source of low digestibility. The fibre treatments were two levels of cellulose powder and one level of barley hulls. The two starch treatments were autoclaved potato starch and autoclaved and raw potato starch (1:1, w/w).

2. The inclusion of raw potato starch reduced true protein digestibility markedly when the protein source was casein, but the corresponding biological values were increased significantly with this treatment. This strongly indicated a movement of urea from the blood to the intestines. This assumption was also supported by significantly lower blood urea concentrations in animals given raw starch. The influence of raw starch on true protein digestibility was, however, significantly less when cellulose and barley hulls were included. This is probably due to reduced transit time from fibre inclusion. The nature of the gut contents also supported this hypothesis.

3. The inclusion of raw potato starch when brown beans were the source of protein had much less effect on true protein digestibility and biological value than when casein was the protein source. This was probably due to the low digestibility of DM and protein in this food leaving sufficient energy and protein for maximum microbial growth. The inclusion of fibre also had little effect on N excretion patterns with the brown-bean diets.

4. An increase in the level of brown bean inclusion reduced true protein digestibility only on the diets containing raw starch whereas the biological value was consistently reduced regardless of starch treatment. The lower biological values were associated with significantly higher blood urea concentrations. Increasing the level of brown bean inclusion also resulted in higher fresh weights of caecum, colon and contents.

5. The present work proves that, through dietary manipulation, it is possible to affect nitrogen excretion patterns in rats.

1. Two experiments with male weanling rats were conducted in which they received individually and restrictedly either a basal semi-purified diet containing starch as the principal carbohydrate or the same diet to which mixed aflatoxins were added in quantities providing from 0·13 to 0·4 mg aflatoxin B1 /kg diet. Various natural ingredients, or semi-purified sources of dietary fibre were substituted for a portion of the starch in the basal diet containing aflaloxin. The diets were fed for 13–14 weeks after which the rats were given ad lib. a commercial rodent diet until they were killed at 109 weeks of age.

2. Two further experiments were conducted in which twenty-four rats in each experimentreceived the basal diet plus aflatoxin, or diets in which a portion of the starch was replaced by gum arabic or by wheat offal. After 13 or more weeksthe absorption, retention and excretion of 14C-labelled aflaloxin B1 was measured in each rat.

3. The addition of gum arabic or wheat bran to the diet decreased the effects of the toxin in the first two experiments, but as measured by several characteristics, only wheat bran provided an effect which persisted during the period when neither it nor the toxin was given. The effects included an apparent reduction in tumour incidence. The change in the content of starch in the basal diet, occurring as a consequence of adding the test ingredients is also considered to be an associated cause of the effects observed

4. In comparison to starch, wheat offal increased the total 14C in the faeces and the proportion of the total found during the first 48 h after dosing. Rats receiving starch excreted more 14C in their urine and retained more 14C in their livers. The differences between gum arabic and starch were not significant as measured by 14C excretion and retention. Liver size as a proportion of carcass weight was less in rats receiving wheat offal or gum arabic, and rats receiving wheat offal had a lower incidence of fat-loaded hepatocytes.

5. The interaction of dietary toxins, or drugs, with the ingredient composition of diet may affect animal response even when the diets are adequate and similar in nutrient composition. This may be of significance both in drug-safety studies and in animal production.

1. The eating and ruminating activity of four rams given long-chopped silage ad lib. in two daily meals was studied by jaw movement recordings. The events of rumination and pseudo-rumination were observed by fluoroscopy and by cineradiography.

2. The rate of eating was highest at the beginning of the main meal and then declined gradually.

3. The silage intake level was low.

4. The swallowed silage did not accumulate at the cardiac region but was forced into the dorsal sac of the rumen by the contractions of the reticulum and cranial sac of the rumen. For regurgitation the solid particles had to return via the ventral and cranial sac of the rumen into the reticulum.

5. Liquid reticular contents with floating solid particles were aspirated into the oesophagus during the maximum of the regurgitation contraction of the reticulum.

6. The rumination activity during the day presented a high proportion of pseudo-rumination cycles whereas during the night the rumination became progressively normal.

7. Pseudo-rumination was caused by delayed return of the fibrous silage particles into the reticulum. Thus in pseudo-rumination the regurgitated material consisted predominantly of fluid containing only a small quantity of solid particles.

8. The results explain why long-chopped silage intake is associated with pseudo-rumination, a lower breakdown of particles and a waste of digestion time.

1. Two groups of ewes were fed on a cobalt-deficient diet throughout pregnancy; one group (group A) was given the diet from the beginning of pregnancy, whilst the other (group B) received the diet for 16 weeks before mating. The ewes in group A continued to receive the diet for 12 weeks post-partum.

2. The vitamin B12 content of serum was estimated on three occasions before parturition and, for group A ewes, at 12 weeks post partum. Urinary concentration of methylmalonic acid was also determined at intervals before the lambs were born.

3. Serum values for vitamin B12 indicated that the ewes in both groups were depleted of the vitamin, though those in group B were more severely affected, as was evidenced by the high incidence of perinatal mortality among the lambs born to these ewes. Perinatal mortality appeared to be associated with abnormally-high values for urinary concentration of methylmalonic acid.

4. Analysis of liver lipids and adipose tissue triacylglycerols of some of the vitamin B12-deprived lambs which died before, or within 1 d of, birth showed that, compared with the corresponding tissues of control lambs, these lipids contained unusually high proportions of odd-numbered fatty acids (mostly 15:0, 17:0 and 19:0). This observation is discussed in relation to the likelihood that, in vitmain B12-deprived lambs, propionate becomes available as a primer unit for fatty acid synthesis when the metabolism of its carboxylation product, methylmalonic acid, is impaired due to partlal lack of a vitamin B12-containing enzyme system.

1. Glutathione peroxidase activity (EC1.11.1.9) and erythrocyte stability were measured in Friesian bull calves which were given for 36 weeks semi-purified diets either adequate or low in selenium or vitamin E or both.

2. Dietary Se or vitamin E content had no effect on growth rate and haematological vaiues. None of the calves exhibited clinical deficiency symptoms and serum aspartate amino transferase (EC 2.6.1.1) and creatine phosphokinase (EC 2.7.3.2) activities remained normal. Heart and skeletal muscles of all calves appeared macroscopically and microscopically normal at autopsy.

3. Glutathione peroxidase activity in plasma, blood and other tissues, except the testis, was significantly lower in calves receiving low dietary Se but was independent of dietary vitamin E content.

4. Plasma vitamin E levels decreased rapidly and to very low levels in calves given low vitamin E diets irrespective of the Se content of the diet.

5. A low dietary vitamin E intake increased the susceptibility of erythrocytes to auto- and peroxidative haemolysis whereas a low Se intake in the presence of adequate vitamin E did not. However, erythrocytes from calves receiving low Se and low vitamin E were more susceptible to peroxidative haemolysis than erythrocytes from calves receiving low vitamin E and adequate Se. The effect of dietary vitamin E content on osmotic haemolysis induced by hypotonic saline was variable.

6. The results suggest that measurement of blood glutathione peroxidase activity and the susceptibility of erythrocytes to auto- or peroxidative haemolysis could be used for the differential diagnosis of subclinical Se and vitamin E deficiency in ruminants.

1. Primary growths of Italian ryegrass and timothy were harvested in late May, high-temperature dried and either retained in the chopped form or ground through a 2 mm sieve and pelleted. All diets were fed to four sheep fitted with re-entrant cannulas into the proximal duodenum and measurements of the sites of energy and protein digestion and the synthesis of volatile fatty acids (VFA) and microbial protein were made.

2. Grinding and pelleting significantly reduced rumen digestion of organic matter and structural carbohydrate(P < 0·05) and the synthesis of rumen VFA (P < 0·01), whilst significantly more digestion occurred in the hind gut, although this was not sufficient to prevent a decline in over-all digestibility on the pelleted diets (P < 0·05). The magnitude of all responses was much larger on the Italian ryegrass diet.

3. Net microbial protein synthesis was 15% less on the pelleted diets but efficiency of microbial protein synthesis was unaffected (mean 188g/kg rumen digested organic matter). Pelleting reduced the degradation of dietary protein from 69% to 47%, and dietary protein represented significantly more of the total protein flowing to the duodenum on the pelleted diets (chopped 28%, pelleted 41%).

4. Over-all, grinding and pelleting reduced total absorbed energy supply by 10% but increased absorbed protein supply by 1 5% which may contribute to some of the improvements seen, in the net energy value of pelleted dlets.

1. Experiments were undertaken to examine the kinetics of large ciliate protozoa in the rumen of cattle on sugar-cane diets.

2. Three Zebu bulls were fed once daily on a diet of sugar cane and wheat bran. The diurnal patterns of volatile fatty acids and ammonia concentrations, and the numbers of protozoa in rumen fluid were determined. The numbers of protozoa reached values of 5 × 104/ml for holotrichs (large ciliates) mainly Isoiricha and Dasytricha spp and 4 × 105 for smaller protozoa, mainiy Entodinia (small ciliates)

3. A method was developed which allowed large ciliate protozoa in rumen fluid to be separated from plant material and bacteria and concentrated in a relatively uncontaminated form. Analysis of these protozoa indicated that 1.8 × 105 large ciliates contained 1 mg nitrogen and approximately 32 mg dry matter

4. A labelled preparation consisting mainly of large ciliates (principally Isotricha spp.) was obtained by incubating isolated protozoa in rumen fluid (free of plant materials) containing [14C-methyl]choline and then isolating them by sedimentation and differential centrifugation

5. A portion of the preparation containing labelled protozoa was incubated in vitro with rumen fluid to determine the turnover of 14C-labelled metabolites. There was no apparent dilution of the label in the protozoa over a 22 h period

6. A major portion of the preparation containing labelled protozoa was returned to the rumen of each of the donor cattle as a single injection. The specific radioactivity in the large protozoa (μCi/mg N) was monitored frequently for over 30 h, and thereafter daily for a further 12 d. The kinetics of tracer dilution were analyzed to give estimates of the size of the pool of these large ciliates in the rumen (24–46 g N), and of their apparent rate of turnover

7. In contrast to the slow turnover of the large ciliates, the rate of turnover of the rumen fluid pool (approximately 54 l), estimated from the rate of dilution of polyethylene glycol, was considerably faster. Large ciliates were therefore selectively retained within the rumen