1. The absorption of zinc by the duodenum of the rat was greatly enhanced at late stages of pregnancy and during lactation.

2. During pregnancy no increase in lysine uptake could be demonstrated, but during lactation, when further increases in Zn absorption occurred, uptake of lysine was increased.

3. The increased absorption of Zn at different stages of pregnancy and lactation appeared to be related to the demand made by the developing foetuses and post-natal offspring.

1.Five sheep were given 400, 625, 850, 1075 and 1300 g lucerne chaff/d according to a 5 × 5 Latin square design to perturbate a mathematical model describing the rate of passage of digesta in terms of rate constants for the reticulo-rumen (k1) and caecum and proximal

2.colon (k2), and a transit time (TT) for the intestines. These values were obtained from the concentration curves of51Cr EDTA and144Ce-144Pr (144Pr) excretion in faeces for comparison with similar measurements obtained directly.

3.The retention times of markers in the reticulo-rumen, caecum and proximal colon and intestines all decreased by approximately 50% as intakes were increased from 400 to 1300 g/d. For both markers, the direct and indirect measures of half-time in the reticulo-rumen were essentially identical. The predicted (indirect) values for half times in the caecum and proximal colon were smaller than the direct values (P < 0.005) but the correlations between them were significant (P < 0.01) for51Cr EDTA (r 0.66) and144Pr (r 0.78). The direct measures of transit time were smaller (P < 0.025) by 5–10% than the predicted values but correlations between them were significant (P < 0.01) for51Cr EDTA (r 0.91) and for144Pr (r 0.93). Thus the model predicted the changes produced in the rate of passage of digesta and its usefulness and limitations are discussed.

3.With144Pr 1/2k1 for the reticulo-rumen and T1/2k2 for the caecum and proximal colon were both positively correlated (P < 0.025) with the organic matter digestibilities. T1/2k2 decreased at half the rate of T1/2k1 with increasing intakes. This would have favoured compensatory digestion in the large intestine.

1. 1. Essential fatty acid-deficient rats were fed γ-linolenic acid (18:3ω6) at 2 % dietary energy and α-linolenic acid (18:3ω3) at 0, 1.6, 2.8 and 4.0 % of the dietary energy.

2. 2. 18:3ω3 at 1.6% apparently inhibits the synthesis of the C20 and C22 ω6 long-chain polyunsaturated fatty acids (ω6 LC-PUFA) metabolized from 18:3ω6.

3. 3. However, increasing the dietary levels of 18:3ω3 from 1.6 to 4.0% has no further influence.

4. 4. The results suggest that dietary 18:3ω6 is an efficient precursor for the ω6 LC-PUFA synthesis even in the presence of 18:3ω3.

1. Four sheep were fed from automatic continuous feeders on whole barley fortified with graded levels of a urea solution. This approach was to a large extent successful in maintaining relatively steady states of rumen ammonia concentration.

2. Rates of barley fermentation in the rumen at various rumen NH3 concentrations were assessed by measuring the disappearance of barley dry matter from polyester bags suspended in the rumen of these sheep.

3. The minimal NH3 concentration for maximal rate of fermentation was estimated as 235 mg/l rumen fluid.

1. 1. The effects of protein-energy malnutrition on brain free amino acids of acidic and neutral groups were investigated in experimental rats.

2. 2. Severe energy restriction did not modify the free amino acid composition of the brain while protein deficiency affected certain amino acids of the brain in opposite directions. Significant decreases in the levels of aspartic acid, threonine and tyrosine were observed in the protein-deficient rats.

3. 3. These changes in brain amino acids appear to be specific to protein deficiency and not affected by energy deficiency.

1. Changes in energy expenditure associated with sleep and activity, age and fatness were measured in sheep. States of vigilance were defined according to electrophysiological records as awake, drowsy, slow-wave sleep (SWS) and paradoxical sleep (PS; Ruckebusch, 1972). Energy expenditure was determined from respiratory exchange. Three groups, each of four sheep were used; yearlings, old (4-6 years of age) fat and old thin sheep. Body fat content was estimated from deuterium oxide space.

2. The amount of time spent by sheep from each group at each state of vigilance was similar, total ‘sleep’ time being 200-250 min/night.

3. The absolute decrease in energy expenditure during drowsiness and sleep was similar for all groups of sheep. The difference between SWS and lying awake was 20-27 J/kg body-weight (W)0.75 per min. Heat production was about the same for SWS and PS.

4. The energy cost of rumination was about 0.34 kJ/kg W per h.

5. The increase in heat production during standing consisted of the energy cost of standing, approximately 0.7 kJ/kg W per h, and the energy cost of changing position, approximately 47 J/kg W.

6. The old thin sheep had a slightly higher heat production on a per kg total W0.75 basis than the old fat sheep, but this difference largely disappeared when heat production was related to ‘lean’ W. On average energy expenditure was approximately 25% lower in the old sheep than in the yearling animals. This difference could not be related to difference in activity or in the energy costs of activity per unit of time.

1. 1. Discrepancies between the results obtained from experiments on pigs with re-entrant duodenal cannulas have been investigated with reference to diet, cannula site and collection procedure.

2. 2. The results obtained from a sealed automatic collection system were different from those obtained from an open manual method and it was concluded that the maintenance of gut intra-luminal pressure in the automatic system was the causative factor.

1. 1. Fractional flux rates of Nτ-methylhistidine (3-methylhistidine; Me-His) of skin and gastrointestine were measured by administering [methyl-3H]methionine to rats.

2. 2. The results showed that the contribution of these tissues to urinary excretion of Me-His was at least 16.6 %. This means that when fractional catabolic rates of myosin and actin were estimated from urinary excretion of Me-His, the part of Me-His derived from skin and gastrointestine should not be neglected.

1. Sheep were given either a basal diet of 107 g crude protein (nitrogen × 6.25)/kg or the same diet to which urea was added to increase the crude protein content to 221 g/kg. Isotope-dilution techniques with [U-14C]glucose and [2-3H]glucose were used to measure various criteria of glucose metabolism. The plasma concentrations of urea and potassium were determined. The sheep were then given the alternative diet and the experiment was repeated.

2. Plasma K concentrations were decreased on feeding urea (P < 0.05).

3. Plasma glucose concentrations were reduced on the urea treatment (P < 0.05), while glucose space and metabolic clearance rate were not significantly reduced (P > 0.05).

4. Some implications for the feeding of non-protein-N to ruminants are discussed.

1. 1. Suckling lambs maintained for 4 weeks on a milk-substitute diet containing 407 g Toprina yeast/kg dry matter of diet exhibited poor growth, low appetite and extensive renal damage.

2. 2. The batch of yeast used contained 2065 mg zinc/kg.

3. 3. The kidneys of lambs offered a milk diet supplemented with the same Zn content as the yeast-fed diet (32.1 mg Zn/1000 kJ) were similarly affected.

1. The effects of diet composition and insulin treatment on blood glucose level, blood amino acid concentrations, the activities of two hepatic gluconeogenic enzymes (fructose diphosphatase, EC 3.1.3.11; phosphoenolpyruvate carboxykinase, EC 4.1.1.32) and of two hepatic glycolytic enzymes (hexokinase, EC 2.7.1.1; pyruvate kinase, EC 2.7.1.40) were examined in rainbow trout (Salmo gairdneri).

2. Blood glucose levels were much higher in trout given a high-carbohydrate (HC) diet than in those given a high-protein (HP) diet. Insulin reduced blood glucose concentration in the HC-fed fish but had no effect in HP-fed fish.

3. Plasma amino acid concentrations were higher in HP-fed trout than in HC-fed trout. Insulin reduced plasma amino acid levels in both groups.

4. Gluconeogenic enzyme activities were higher in HP-fed trout than in HC-fed trout. Insulin reduced phosphoenolpyruvate carboxykinase activity in HP-fed trout but had no effect on either enzyme activity in the HC-fed trout.

5. Pyruvate kinase activity was greater in HC-fed trout than in HP-fed trout. Insulin did not affect pyruvate kinase activity in the HC-fed trout but reduced it in HP-fed trout.

6. Hexokinase activity was not affected by the diet treatments used, but was enhanced in the trout treated with insulin. Glucokinase (EC 2.7.1.2) was not detected in any of the trout livers.

7. The results suggest that the inability of trout to control blood glucose concentration is partly due to a lack of glucose-phosphorylating capacity. Gluconeogenesis is controlled in response to diet and insulin by changes in enzyme level and by variation in concentration of gluconeogenic substrates.

1. Measurements were made of the losses of nitrogen in the faeces and urine of sixty pigs of approximately 33 kg, given dietary regimens comprising twenty-nine combinations of fish flour (0-800 g/d) and maize starch (0–1200 g/d).

2. The results were used to develop a generalized equation describing N retention as a joint function of N intake and starch intake.

3. The protein-sparing effect of starch was exerted in all circumstances. It was greatest when protein intake exceeded 220 g/d but some effect persisted with protein-free diets. With a high protein supply, the increase in N retention per unit increase in dietary starch decreased from 36 mg/g with the first increment to 3 mg/g with the highest attainable starch intake.

4. From the generalized equation the relationships between net protein utilization and protein concentration and food intake could be described as continuous functions. The equations may be of use in comparing the protein values of diets measured under non-standardized conditions.

1. In five experiments with growing female pigs of 38–63 kg, insulin (2 mU/kg per min) and glucose (9–17 mg/kg per min) were infused continuously for 3–7 d. In three further experiments, glucose (9 mg/kg per min) was infused alone for 5 d.

2. In response to the combined infusion, plasma insulin increased 2-7-fold, plasma glucose decreased, on average, by 50% and plasma urea concentration was reduced by 40%. Urinary excretion of urea and nitrogen decreased after the first day of infusion to values averaging 70% of control levels.

3. The infusion of glucose alone provoked only a small increase in plasma insulin. The reduction of urinary urea and of N excretion were approximately 25% of those observed with the combined infusions.

1. Mean daily nutrient intakes of 195 women in the first trimester of pregnancy were assessed by weighed dietary records.

2. In comparison with recommended intakes for non-pregnant women aged 18-55 years (Department of Health and Social Security, (1969), more than two-thirds of the subjects were having insufficient energy, iron and cholecalciferol. Unsatisfactory intakes of other nutrients were not uncommon. In relation to recom mended intakes for the second trimester Department of Health and Social Security, (1969), all mothers were having insufficient cholecalciferol and more than 80 % of mothers had unsatisfactory intakes of energy and Fe.

3. Intakes appreciably lower than those recommended were associated with the following factors: social classes III, IV and V; maternal age under 20 years; smoking ten or more cigarettes daily; vomiting on more than 3 d/week.

1. The B-vitamins in milk from baboons (Papio cynocephalus) at various stages of lactation were measured microbiologically.

2. Mature milk contained, on average (μg/ml): thiamin 0.18, riboflavin 0.74, nicotinic acid 3.2, folate 0.03, vitamin B6 0.70, vitamin B12 0.002, pantothenic acid 2.63, biotin 0.0065.

3. Colostrum contained much less vitamin B6 and pantothenic acid than mature milk; otherwise, there were only slight changes in composition as lactation progressed. Neither these changes, nor the absolute values, resembled those for human or cow's milk.

4. The average daily secretion of B-vitamins in milk represented less than 10% of the mother's dietary intake; that of folate was less than 0.5% of the mother's dietary intake.

5. Baboon milk was calculated to provide infants with approximately the following quantities of B-vitamins (/d): thiamin 0.06 mg, riboflavin 0.25 mg, nicotinic acid 1.1 mg, folate 10 μg, vitamin B6 0.25 mg, vitamin B12 0.7 μg, pantothenic acid 0.9 mg, biotin 2.2 μg.