1. In order to establish whether or not there is a relationship between the blood ketone-body concentrations and the potential ability of the liver to synthesize ketone bodies in sheep on varying nutritional regimens, a study has been made of the concentrations of acetoacetate and 3-hydroxybutyrate in blood and the activities of enzymes concerned with ketogenesis in liver of developing sheep from mid-way through gestation to maturity, in pregnant ewes from mid-way through pregnancy and in starved pregnant and non-pregnant ewes.

2. During development the most marked change in blood 3-hydroxybutyrate concentration occurred when the lambs were weaned. Blood acetoacetate concentrations did not change during development. When mature ewes were starved both 3-hydroxybutyrate and acetoacetate concentrations in blood were increased.

3. Changes found in the activity of 3-hydroxybutyrate dehydrogenase (EC 1.1.1.30) in the liver were correlated with the changes in blood 3-hydroxybutyrate concentrations during development but no such relationship existed in pregnant or fasted ewes. No correlation was found between the ability of the liver to synthesize acetoacetate and blood ketone body concentrations in either developing or pregnant adult sheep. The rate of acetoacetate production expressed per g liver increased during foetal life but values observed in lambs 1 d after birth were similar to those found in suckling and mature sheep. During the last month of pregnancy and when non-pregnant sheep were starved the hepatic potential for ketogenesis was increased. During development the activity of acetyl-CoA acetyltransferase (EC 2.3.1.9) was correlated with the rate of hepatic acetoacetate production.

4. These changes have been contrasted with those that occur in developing and starved adult rats.

5. It is concluded that hepatic production of ketone bodies cannot be the only factor in the regulation of blood ketone body concentrations in developing and pregnant sheep.

1. Two experiments, involving six lactating Landacre x (Landrace x Large White) sows were undertaken to study the lysine requirement of the lactating sow and to identify the second limiting amino acid by means of interpretation of plasma amino acid and blood urea levels.

2. A basal diet composed mainly of equal amounts of ground barley and ground wheat supplemented with mineral and vitamin mixtures was used. This diet was supplemented with synthetic amino acids (lysine, threonine, tryptophan, methionine and isoleucine).

3. Plasma amino acid and blood urea values showed a close agreement and indicated that lysine intake above 38.4 g/d was in excess of the requirement level.

4. Plasma amino acid values suggested tryptophan to be the second limiting amino acid whereas blood urea values suggested threonine to be the second limiting amino acid.

1. The amounts of copper and zinc in the foetuses of ewes carrying from one to four lambs were measured at different stages of gestation and estimates were made of the amounts of these metals in their livers.

2. The accretion of Cu and Zn could be described by growth equations of the Gompertz form, from which could be derived estimates of the instantaneous and fractional rates of deposition of these metals in the foetal body.

3. Between the 80th and 144th day of gestation the instantaneous rates of deposition of the metals increased exponentially, and at the end of pregnancy were calculated to be 0.24 and 2.0 mg Cu and Zn/d respectively in the triplet lamb foetus. The corresponding total accretions were estimated to be 10 and 69 mg respectively.

4. The fractional rates of live-weight gain and of deposition of Cu were similar and decreased at similar rates; that of Zn deposition decreased much more slowly.

5. The proportion of whole-body Cu estimated to be in the liver was always greater than 50 %. The amount of Zn in the liver remained constant and contributed 72 % of the total body Zn at 80 d but only 8 % at 144d.

6. The relative amounts of Cu and of Zn accrued per unit body-weight gain were not constant during the development of the foetus. As foetal numbers increased the amounts of each metal deposited in the foetus decreased more rapidly than did foetal weight.

7. The results are discussed in relation to the demands for Cu and Zn during pregnancy in sheep.

1. The effect of 1-α-hydroxycholecalciferol (1 α-OH-D3) on calcium and phosphorus metabolism has been studied in ewes at peak lactation by a combination of a mineral balance and a radioisotope technique.

2. The rate of Ca absorption was substantially higher in the treated ewes than in controls. The rates of endogenous loss of Ca into urine, faeces and milk, however, were only slightly higher.

3. In consequence, the net retention of Ca was increased and the loss of skeletal reserves of Ca normally associated with peak lactation, prevented.

4. Although the rate of bone accretion increased slightly, the increase in skeletal retention of Ca resulted mainly from a decrease in the rate of bone resorption.

5. This finding conflicts with the generally held belief that bone resorption is increased by cholecalciferol treatment.

6. The rates of apparent absorption and retention of P were increased by the treatment probably as a result of a direct effect of the 1α-OH-D3 on P absorption.

7. These results provide a possible explanation of the beneficial effect of 1α-OH-D3 in preventing parturient paresis (milk fever) in the dairy cow.

1. Breath hydrogen and methane were measured in eight normal individuals after acute and separate administration of different chemical components of dietary fibre.

2. Hemicellulose, raffinose and lactulose increased H2 production, while cellulose, pectin and lignin did not. Methane production was found to be individual and unaffected by any of the substances. Differences in physical properties of the same chemicals appear to have no influences on H2 and CH4 production.

1. Male Sprague–Dawley rats were given 630 g/kg sucrose or starch with 2 mg/kg aflatoxin B1 for periods of 75, 145 and 200 d, and the 24 h urinary excretion of aflatoxin M1 was measured.

2. Less aflatoxin M1 was excreted by the rats fed on the sucrose-rich diet compared to those fed on the starch-rich diet. This difference was especially marked when expressed per g metabolizing tissue.

3. It is concluded that sucrose probably decreases the activity of aflatoxin B1 metabolism in a similar way to its previously found effect on the drug-metabolizing enzyme.