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Studies carried out over several years on a tropical estuary, the Ross River Estuary, have shown that copper speciation is influenced by both terrestrial and marine humic substances. While terrestrial humic substances are mobilized by high freshwater runoff in the monsoonal season, Trichodesmium blooms mobilize high concentrations of marine humics to the inshore zone and increase labile forms of copper. The marine humics are more soluble than the terrestrial humics and persist in coastal waters of the Great Barrier Reef lagoon for many months prior to the wet season.

Two groups each of four Merino wethers, two years old and in very lean condition after many weeks on a straw ration, were fattened on a ration of lucerne hay. One group of animals drank 1.3 per cent sodium chloride solution for 16 weeks before and during fattening while the control group drank tap water throughout. Analyses done after body weight increases of about 12 kg showed that, compared to the controls, the saline drinking group had significantly less fat, more water, and more protein in the edible carcase. All differences were significant. Samples of fat from the omentum and perirenal area showed a tendency towards a higher degree of unsaturation in the saline-drinking animals although these results were not statistically significant.

The influence of sodium chloride ingestion via the drinking water upon the mineral balance in sheep has been examined. Four Merino ewes were offered rainwater containing zero, 0.8, or 1.3 % sodium chloride as the only source of drinking water. After correction for variations in mineral intake, the data showed that the urinary excretion of calcium, magnesium, potassium, phosphorus, sodium, and chloride was increased by saline water ingestion. The faecal excretion of calcium, magnesium, and phosphorus was not affected by the inclusion of sodium chloride in the drinking water, but faecal potassium was decreased and sodium and chloride increased. The drinking of saline water by the sheep resulted in a decline in the calcium, phosphorus, and potassium balances, an increase in the sodium and chloride balances, and no change in the magnesium balance. The sodium balance was negative for the rainwater treatment, but all other balances were positive. Saline water ingestion also caused an increase in the glomerular filtration rate, a decline in plasma magnesium levels, and an increase in plasma potassium levels. It is concluded that saline water ingestion causes alterations in the pathways of excretion of minerals and the mineral balances in sheep, but the changes would appear to be of insufficient consequence to have detrimental effects.

Tritiated water has been used to compare the water turnover rates and water spaces in sheep which had become accustomed to consuming 1.3 % salt water with those of sheep allowed to drink fresh water. The sheep drinking the saline water (mean body weight 42.0 kg) had mean turnover rates of 207 ml/kg/day compared with 90.3 ml/kg/day for sheep drinking fresh water (mean body weight 38.3 kg). The sheep on salt water revealed a mean tritiated water space of 27.5 kg while that of the sheep on fresh water was 23.5 kg.

In each of three experiments the acetic, propionic, and butyric acids in the rumen of a sheep were labelled with 14C and a sample of the rumen contents was removed to an artificial rumen so that fermentations of the same substrates could be conducted simultaneously in vivo and in vitro. The in vitro fermentations were carried out in a specially designed artificial rumen of the "permeable" type in which the volume of the contents was kept constant while a continuous supply of artificial saliva was introduced. The relationships between the specific activities of the volatile fatty acids during a period of 2 to 3 hr indicated that the relative rates of formation of the acids were similar in the two systems, although in each experiment the fermentation appeared to proceed more slowly in vitro. It is considered that the procedure constitutes a stringent test for the correct functioning of an artificial rumen.

The distribution of zinc recently absorbed as 65Zn into subterranean clover (T. subterraneum L. var. Bacchus Marsh) from culture solutions has been examined by means of radioautographs in normal plants and in plants recovering from a state of zinc deficiency. In normal plants which had been grown initially in cultures containing non-radioactive zinc, the recently absorbed zinc reached high concentrations in the roots, main axis, and youngest leaves but very little of it moved into the older, fully expanded leaves. In plants recovering from the deficiency, on the other hand, the recently absorbed zinc reached high concentrations in all the living organs, including the oldest leaves. Growth of the "little" leaves or other leaves affected by the deficiency was not resumed after the entry of zinc into their tissues. Recovery of the plant depended upon the production of new leaves by the leaf primordia and upon their subsequent growth and emergence.

The rates of production of acetic, propionic, and butyric acids in the normal rumen of a sheep have been measured from the decline in specific activity of these acids in the rumen after introduction of their sodium salts, labelled with 14C. Polyethylene glycol was introduced into the rumen to permit measurement of the rumen volume. The rates of production were: acetic acid 99 m-moles/hr, propionic 44 m-moles/hr, and butyric 21 m-moles/hr.

Young plants of subterranean clover (T. subterraneum L. var. Bacchus Marsh) were grown between day 20 and day 43 in culture solutions containing zinc labelled with the radioactive isotope 65Zn and were then transferred to zinc-free culture solution. The distribution of labelled zinc in the plant parts during the subsequent onset of zinc deficiency was determined by means of radioautographs. By similar means the distribution of labelled zinc was determined in plants transferred to culture solutions containing inactive zinc. The zinc present in fully expanded living leaves was largely retained there while they remained alive, even during the onset of zinc deficiency which progressed to the "little leaf" stage. Some zinc was transported out of these leaves when they became prematurely senescent as a result of the deficiency. During the onset of the deficiency some zinc was transported out of the roots and the main axis. After zinc deficiency had become acute and growth had practically ceased, the concentration of zinc in the youngest leaves at the growing points of the main axis and runners remained higher than that in the slightly older, fully expanded leaves.

Subterranean clover (T. subterraneum L. var. Bacchus Marsh) was grown to maturity in a culture solution containing zinc labelled with the radioactive isotope 65Zn. The distribution of zinc in the plants at different stages of growth was determined by means of radioautographs. These show that zinc is always present in very high concentration in the terminal portions of the main axis, runners, and laterals, in young, expanding leaves and petioles, in root tips and at points along the roots, in parts of the inflorescences, and in developing and mature seeds. The concentrations decrease in the vegetative organs as they expand and mature. In mature vegetative organs there is usually a higher concentration of zinc in the vascular tissue than in the tissue surrounding it. A higher concentration of zinc is found in the nodes of the runners and laterals than in the internodes. In the nodes themselves the concentration is highest where the amount of vascular tissue is increased by the presence of the vascular traces of petioles and of runners, laterals, or branches.

Changes in the distribution of dry weight, and of zinc and copper, between root plus stem and the leaflets and petioles of the individual leaves of young plants of Trifolium subterraneum L. var. Bacchus Marsh grown in zinc-deficient culture solution, have been traced during a period of 3 weeks. These changes were compared with those which took place in control plants grown in a culture solution which was adequately supplied with zinc. In control plants the dry weight and zinc content of each leaf exceeded that of the previous one. The dry weights of the cotyledons, the primary leaf, and the first trifoliate leaf on these plants began to decrease slowly after reaching a maximum, but there was no decrease in the dry weights of the younger leaves during the period of observation. The zinc content of each leaf on the control plants began to decrease rapidly after it had reached a maximum. Maximum zinc content was reached before maximum dry weight. These changes in dry weight and zinc content led to a decreasing concentration of zinc in each leaf as it emerged and unfolded, and they were responsible for wide differences between the concentrations of zinc in the leaves present at any one time. Symptoms of zinc deficiency were recognizable 25 days after germination in the plants grown in zinc-deficient cultures; a distinctive chlorosis appeared in the second trifoliate leaf when the leaflets began to unfold. Development of the third leaf was retarded and that of the fourth arrested in the affected plants, but the dry weight of the whole plant continued to increase at almost the same rate as that of control plants for a week after the chlorosis was first observed. The reason for this was traced to an abnormal increase in the weight of each of the oldest leaves after the onset of zinc deficiency. Zinc was transported more rapidly out of the cotyledons and primary leaf of zinc-deficient plants than out of corresponding leaves of control plants. The amounts of zinc in the trifoliate leaves of zinc-deficient plants were much less than those in corresponding leaves of the controls: a decreasing concentration of zinc which was observed in the trifoliate leaves of zinc-deficient plants was brought about by increases in dry weight without any appreciable change taking place in the amounts of zinc present. The changes that were observed in the concentrations of zinc in individual leaves of zinc-deficient and normal plants indicated that zinc was present in the leaves in highest concentration before they emerged and unfolded. Radioautographs showing the distribution of 65Zn in young plants confirmed this. Copper was transported out of the cotyledons of control plants. It was also transported out of the primary and trifoliate leaves of these plants, but only after a period of accumulation. The leaves took longer to accumulate a maximum amount of copper than to accumulate a maximum amount of zinc. The onset of zinc deficiency did not have a marked effect on the concentration of copper in the leaves, because abnormal increases in the dry weights of the leaves were accompanied by corresponding accumulations of copper.

Changes in the distribution of zinc, copper, and dry matter in seedlings of Trifolium subterraneum L. var. Bacchus Marsh grown in solution cultures which were supplied with copper but not with zinc have been traced during the first 40 days after germination. Increase in total dry weight was accompanied by a rapid decline in the concentration of zinc in the plant parts examined. Symptoms of zinc deficiency were recognizable in the third trifoliate leaf by the time the leaflets opened, 33 days after germination. At that time the concentration of zinc in leaf plus petiole had fallen to 14 p.p.m. in the dry matter. There was a continual net loss of zinc from the cotyledons. A marked increase in the amount of copper present in roots, and in leaf plus petiole, occurred soon after the addition of copper to the cultures 20 days after germination, but no substantial change was observed in the amount of copper present in the cotyledons or in the hypocotyl plus growing point. These latter tissues had previously lost small amounts of copper.

The distribution of dry weight and of zinc and copper at different stages of growth has been examined in Trifolium subterraneum L. var. Bacchus Marsh grown in culture solutions to which graduated amounts of zinc were added. Several characteristics of the growth of the plants were assessed quantitatively. Symptoms of zinc deficiency developed in cultures which were supplied with suboptimal amounts of zinc.

Radioactive isotopes of copper, molybdenum, and selenium have been applied to a number of soils in order to study the movement of these trace elements under the influence of various fertilizer treatments. With soils of moderate exchange capacity the copper remained near the surface following all fertilizer treatments and the equivalent of several years' rainfall. With light soils of low exchange capacity some penetration of copper occurred, especially following superphosphate and an aqueous extract of lucerne. With molybdenum in general a high proportion of this element was leached right through the soils, except in the case of the two laterite soils examined, where up to half of the molybdenum was retained near the surface. Selenium applied as sodium selenite was intermediate between the extremes illustrated by copper and molybdenum, in that a high proportion was retained by the calcareous soils but not necessarily at the surface. The lighter soils retained a much lower proportion of selenium.

l(a). Volatile fatty acid (VFA) production (moles/12 hr) by two sheep fed at 2-hourly intervals on a constant ration containing equal parts of wheaten hay and lucerne hay, showed no significant difference between the sheep or between day-time and night-time values. The precision with which production could be measured over a series of 12-hr periods is given. The quantities of VFA produced in the rumen on successive days varied considerably; the extent of this variation was similar to that occurring in the quantities of faeces passed. (b) Production remained much the same whether the sheep were fed at intervals of 1, 2, or 12 hr.(c) The energy of the VFA produced in the rumen was equivalent to about 54% of the digestible energy of the diet. 2. Similar amounts of VFA were produced from two different mixtures of wheaten hay and lucerne hay, and from lucerne hay alone. 3. A modification in the procedure for measuring VFA production was tested and found to be satisfactory. The necessary apparatus could be readily carried on the back of a freely moving sheep.

(1) In sheep fed at 12-hr intervals on roughage diets (lucerne and wheaten hay) total volatile fatty acid production in the rumen has been measured by an isotope dilution procedure based on the infusion of a single 14C-labelled volatile fatty acid. (2) Total and individual acid production has been measured through the infusion of a mixture of 14C-labelled acids in which the proportions of individual acids were such that transfers of 14C by interconversions between the acids were balanced. (3) The findings support the view that the mixture of acids produced in the rumen is similar in composition to that present in the rumen fluid throughout the feeding cycle. Consequently it was possible to determine the production of individual acids by a relatively simple procedure requiring only the infusion of a single 14C-labelled acid and measurement of the concentration of 14C in a composite sample of the acids in the rumen fluid collected throughout the feeding cycle. This procedure is considered suitable for routine use; automatic sampling of rumen fluid still further reduces the work involved. (4) The infusion of certain mixtures of 14C-labelled fatty acids showed that the composition of the acid initially formed in the rumen was acetic 77–83%, propionic 15–18%, and butyric 1–7% according to the diet given and the time elapsed after feeding. From 50 to 80% of the butyric acid in the final volatile acid product was formed from acetic acid. Degradation of 14C-labelled butyrate formed from [1-14C] acetate in the rumen showed 93% of the 14C to be nearly evenly divided between carbon atoms C1 and C3.

(1) Production of volatile acid in the rumen of sheep fed at 12-hourly intervals on a mixture of wheaten hay and lucerne hay has been measured by two isotope dilution procedures involving continuous infusion of 14C-labelled fatty acid into the rumen and determination of the concentration of 14°C in the rumen acid throughout the feeding cycle. In the first procedure the varying rate of production was matched by a varying rate of infusion so that a constant concentration of label was maintained in the rumen acid. In the second procedure a constant rate of infusion was maintained and a mean value obtained for the concentration of label in the rumen acid during the cycle. Production values calculated from the data from both procedures were similar: approximately 5 moles of volatile acid were produced per kilogram of dry fodder. (2) This same rate of production was found for rations of 360, 450, and 675 g dry fodder fed at 12-hourly intervals.

Lucerne (Medicago sativa L.) in which the proteins were labelled with radioactive selenium was fed to mice. The distribution of 75Se among the various organs was studied. On the basis of 75Se activity per unit wet weight, the importance of the liver and kidney as metabolic sites is confirmed, and attention is directed to the pancreas, endocrines, and the stomach wall as additional sites where selenium is present in comparable concentrations. The relative importance of the above organs is supported by the results of autoradiography; in addition, this demonstrates the high concentration of 75Se in the cell nuclei, where selenium may play a fundamental role. Radioactive selenium from labelled lucerne was found in the milk of a lactating mouse within 4 hr of it being fed. Within 24 hr approximately 20% of the selenium absorbed by the dam had been transferred to the young mice through the milk.

In an area where the selenium concentration in the pastures appeared barely adequate, and where growth rate of lambs was commonly poor, experiments were conducted with 300 lambs during four successive years, to study the effects of supplements of selenium, cobalt, selenium plus cobalt, and vitamin E. The absence of any effect of treatment with selenium (or the other supplements) on growth rate, wool production, or level of glutamic-oxalacetic transaminase in the serum indicated that selenium deficiency did not affect the sheep during the experimental period. The toxic effects of regular oral doses of large amounts of selenium (up to 600 gSe/kg/day) were studied on 50 mature wethers for periods up to 15 months. Food consumption and body weight increase were depressed by 200 gSe/kg/day, and food consumption by 300 g, while some mortality occurred at 400 g. The selenium concentration in the blood and the tissues increased with rate and duration of intake; that in the tissues fell gradually after dosing with selenium was discontinued. No pathological changes were observed in the tissues of the sheep that survived the selenium treatment. It is unlikely that the amounts of selenium required to prevent selenium deficiencies in sheep will prove toxic to the animals.