Iron dynamics in the ruminant.

We have compared the plasma clearance rate of radioactive iron in cows both as ferric chloride and as iron specifically bound to transferrin. We have also repeated the transfusion experiment of Dern et al. (Dern, R.J., Monti A. and Glynn, M.F. (1963) J. Lab. Clin. Med. 61,280-291) using goats. The results show that neither non-specificity bound iron (Bates, F.W. and Schlabach, M.R. (1973) J. Biol. Chem. 248, 3228-3232) nor the iron bound to the two different sites in transferrin (Awai, M., Chipman, B. and Brown, E.B. (1975) J. Lab. Clin. Med. 85,769-784) can be identified as distinguishable iron pools by this technique.

Manganese metabolism in cows and goats.

When 54MnCl2 was incubated with fresh bovine or caprine serum for 20 h and the serum subjected to electrophoresis at pH 9.5, the 54Mn bound to transferrin and alpha2-macroglobulin in proportions which varied with the temperature of incubation and the temperature of electrophoresis. Between 0 and 37 degrees C, the higher the temperature of incubation the larger the proportion bound to transferrin and the lower the proportion bound to alpha2-macroglobulin. The temperature at which electrophoresis was performed had little effect on the proportion of 54Mn bound to transferrin, but increasing temperature reduced the proportion of 54Mn bound to alpha2-macroglobulin. Mn2+ did not bind to purified transferrin in vitro in the absence of an oxidising agent. In the presence of permanganate, Mn3+ was formed and chelated by transferrin at physiological pH. In fresh serum this oxidation step may be performed by ceruloplasmin or molecular oxygen. Mn2+ was bound reversibly to alpha2-macroglobulin but this protein played no part in the oxidation of divalent manganese and had no effect on the protein binding of trivalent manganese. Manganese in the divalent state, either free as Mn2+ or bound to alpha2-macroglobulin, is removed from blood plasma very efficiently by the liver. However, the manganic-transferrin complex normally found in circulation is not rapidly removed from plasma. The liver can remove large amounts of excess manganous manganese which it presumably excretes; the small essential fraction of the manganese absorbed is oxidised to the trivalent state and bound to transferrin.

The development of acid-base reaction cements as formulations for the controlled release of trace elements.

Novel acid-base reaction cements have been developed for use as controlled release formulations. Many new ones have been discovered and assessed; these include those which are capable of releasing copper, cobalt or selenium singly or in combination. A selection was made of the most suitable formulations for this purpose and these were subjected to field trials.

Virulence of Bordetella bronchiseptica from pigs with or without atrophic rhinitis.

The virulence of 17 isolates of Bordetella bronchiseptica from 13 pig herds was compared by intranasal infection of gnotobiotic piglets and LD50 tests on mice. Of 59 piglets given 8.1-10-5 log 10 colony-forming units (cfu) of isolates from two herds with atrophic rhinitis (AR isolates) or isolates from six unaffected herds (non-AR isolates), 16 died of acute pneumonia; the survivors developed non-progressive turbinate hypoplasia and chronic pneumonia. Infection of 11 piglets with c. 3.0 log to cfu of three AR isolates or three non-AR isolates caused turbinate hypoplasia, but only slight pneumonia and no deaths. There were no significant differences between the virulence of AR and non-AR isolates in piglets. In LD50 tests in mice, there were no significant differences between the results from six AR isolates and six non-AR isolates, or from toxin prepared from two AR isolates and one non-AR isolates was fairly uniform, and that other factors must be responsible for the occurrence of progressive lesions of atrophic rhinitis in some but not all infected herds.

Calcium mobilisation in hypomagnesaemic cattle.

Intravenous infusions of EDTA solution (4.7 per cent w/v) were used to induce hypocalcaemia in six steers and six non-pregnant lactating Friesian cows, once when they were normomagnesaemic and once when they were hypomagnesaemic (less than 0.85 mmol Mg per litre) and their rates of calcium mobilisation have been measured. The mean rates of calcium mobilisation by the normo- and hypomagnesaemic steers were 0.32 mmol/min and 0.21 mmol/min respectively (P less than 0.005) and the mean calcium mobilisation rates of the cows were 0.41 mmol/min and 0.26 mmol/min respectively (P less than 0.02). It is concluded that hypomagnesaemia reduced the calcium mobilisation rate in both steers and non-pregnant lactating cows.

The absorption of dietary manganese by dairy cows.

Additional manganese, sufficient to increase the dietary concentration to approximately 1000 mg/kg, was administered to one cow for four and another for seven days. Manganese concentrations in portal and mesenteric plasma were increased by a mean of 3.9 microgram/litre above the concentration in systemic plasma. This increment is equivalent to the absorption of 0.54 per cent of the administered manganese. The cow which received manganese for seven days showed after six days larger increases in systemic plasma manganese concentration which may indicate a toxic effect of excess manganese upon the liver.

The half-life of glutamate dehydrogenase in plasma of dry and lactating dairy cows.

The clearance of glutamate dehydrogenase from plasma was measured weekly for three weeks in three dry and three lactating cows. The clearance was exponential with a mean clearance constant of 0.0488/j and means (+/- SE) half-life of 14.2 (+/- 0.77) h. There were variations among cows and among measurements in the same cow but there was no difference between the mean half-lives of GDH in lactating and dry cows. Because of the long half-life the small variations among individual cows are unlikely to affect the interpretation of increased plasma GDH activity.

Importance of water for the health and productivity of the dairy cow.

Four lactating Friesian cows (average weight 485 kg, milk yield 22 kg d-1) were maintained in completely controlled circumstances and deprived of water for 72 hours. During this period they were carefully monitored and lost 100 kg in bodyweight, principally accounted for by cumulative losses of water in milk, urine, faeces and respired air. The mean rates of respiration and rumen contraction decreased by approximately 50 per cent. Mean body temperature increased by 0.5 degrees C, but pulse rate did not change significantly. Dry matter intake, particularly of hay, decreased rapidly to less than 10 per cent of normal on the third day. Milk yield decreased only slightly during the first 24 hours but on the third day the average yield was only 28 per cent of normal; the composition of the milk did not change significantly. There were significant progressive increases in serum sodium concentration (after four hours water deprivation), osmolality (after 24 hours), urea (after 38 hours), copper (after 48 hours) and magnesium and total protein concentration (after 62 hours); packed cell volume (measured with a Coulter Counter) increased after 38 hours but packed cell volume (determined in a microhaematocrit centrifuge) increased only after 62 hours. In spite of the dehydration the cows showed no signs of distress. Within 48 hours of the cows being given free access to water, bodyweight, appetite, milk yield and blood composition had returned almost completely to normal.

Accidental contamination of the public water supply at Lowermoor, Camelford: an assessment of the possible veterinary consequences.

As a result of the delivery of 20 tons of concentrated aluminum sulphate solution into the wrong part of the Lowermoor water treatment works the water supplies of 20,000 people and many thousands of cows, sheep, pigs and poultry became contaminated with aluminium, copper, zinc and lead. When the water mains were flushed into the rivers Allen and Camel many fish were killed by the high concentrations of aluminium. However, there appear to have been no detrimental effects on farm live-stock; this was either because the animals were likely to have ingested less of the toxic elements from the water than they ingest with normal components of their diet, including soil, or because the abnormally high intakes lasted for only a short time.

Magnesium and milk fever.

There is clinical, experimental and theoretical evidence for a connection between the occurrence of subclinical hypomagnesaemia and the incidence of milk fever. Clinically, pregnant dry cows in dairy herds with a high incidence of milk fever have often been observed to have subnormal blood magnesium concentrations. Experimentally, it has recently been shown that subclinical hypomagnesaemia reduced the ability of cows to mobilise calcium in response to hypocalcaemia; a response which is essential if cows are to avoid milk fever. And theoretically there are several points in the biochemical pathways for calcium where a need for magnesium has been demonstrated in laboratory rodents. These connections between subclinical hypomagnesaemia and milk fever are explored and their consequences for the prevention of milk fever are considered.

Effects of low level dosing of iron on the haematology and growth rate of piglets.

Of 472 piglets (56 litters), half reeived 200 mg and half received 100 mg of iron as iron dextran administered intramuscularly as a single dose into the ham muscles between the first and fourth day after birth. The piglets were weaned at about three weeks of age, at which time those given 200 mg of iron had higher values of all haematological components. However, there was no significant difference between the mean daily live-weight gains of the two groups, and 100 mg iron maintained haematological components above levels associated with anaemia. It is suggested that 100 mg iron as iron dextran is adequate for piglets weaned at three weeks of age.

Study of combined injections of 1 alpha-hydroxy-cholecaldiferol and cloprostenol in the prevention of parturient paresis.

Dairy cows were injected with 1 alpha-hydroxycholecalciferol (1 alpha-HCC) and, or, cloprostenol at 275 days of gestation. Blood samples were taken daily from 270 days of gestation until seven days after parturition and analysed for calcium, inorganic phosphate, magnesium and hydroxyproline. In all treated and control cows concentrations of calcium, inorganic phosphate and magnesium decreased around the time of parturition. Concentrations of hydroxyproline increased from the second to the fourth day after parturition. This increase was slightly smaller in cows injected with cloprostenol but was unaffected by 1 alpha-HCC. There was a greater indicence of retained placenta and endometritis in cows receiving cloprostenol. The injection of cloprostenol with 1 alpha-HCC at 275 days of gestation did not prevent milk fever.

Barium selenate injections in cattle: effects on selenium concentrations in plasma and liver and residues at site of injection.

Twenty Angus cross heifers were fed a complete diet which contained 0.07 mg selenium/kg dry matter. Thirteen were injected subcutaneously with barium selenate at a dose rate of approximately 1 mg selenium/kg bodyweight and seven remained untreated. All the heifers were slaughtered during the following 121 days, the last of the treated group 119 days after injection. Glutathione peroxidase activity in blood increased within four weeks of administration and remained high thereafter. The selenium dependent glutathione peroxidase activity did not increase in liver kidney or muscle. The concentrations of selenium in the blood, liver and muscle were increased significantly from 30 days until 119 days. Between 76 and 99 per cent of the selenium injected remained at the site of injection.

The effects of reducing manger space on dairy cow behaviour and production.

The manger space for a group of 30 cows was reduced from 105 cm to 15 cm per cow during a period of six weeks. Before each reduction in manger space the cows were observed for 24 hours and their activity and aggressive behaviour recorded. The activity of individual cows varied little but there was wide variation among cows. The reduction in manger space did not change the mean number of visits by cows to the manger, the total time spent feeding, the amount of aggressive behaviour, the milk yield or the general activity of the cows in comparison with a control group allowed 105 cm of manger space per cow for the whole period. There was a reduction in the total time spent feeding by cows which were clinically ill and a change in the number of visits made to the manger by cows in oestrus. A reduction in the allocation of manger space would make it possible either to build smaller, cheaper housing or to convert existing buildings to accommodate more cows. It would also make it possible to use automated systems to record the feed intake and number of visits to the manger of individual cows and would help to detect cows which were sick or in oestrus.

Boluses of controlled release glass for supplementing ruminants with cobalt.

Boluses of controlled release glass containing cobalt and weighing approximately either 60 g or 14.5 g were administered to 22 steers and 21 sheep respectively. The steers were housed and slaughtered at intervals between 17 and 145 days after dosing. The boluses released more than 0.85 mg cobalt daily. In both untreated and dosed animals serum and liver vitamin B12 concentrations were at the upper end of the normal range. Two types of glass were administered to sheep. In five wethers one glass released 0.07 mg cobalt per day, and in 16 grazing lambs a second glass released more than 0.15 mg cobalt per day. Fourteen of the boluses were recovered from the lambs up to 276 days after dosing. The concentration of B12 in serum of lambs increased significantly from a mean +/- sd of 1.64 +/- 0.47 to 2.02 +/- 0.04 ng/ml serum and the concentration in liver from 3.84 +/- 0.85 to 4.99 +/- 0.72 micrograms/g dry weight liver.

Boluses of controlled release glass for supplementing ruminants with copper.

A controlled release glass was formulated into boluses weighing approximately 17 g or 75 g and administered to 19 lambs and 20 steers respectively. The animals were at pasture during the summer months. The lambs were slaughtered between 57 and 219 days after dosing when the mean concentration of copper in their livers had increased to 107.8 +/- 33.4 mg copper/kg fresh weight compared with 55.9 +/- 23.0 mg copper/kg fresh weight in undosed controls. The steers were slaughtered more than 140 days after dosing; the mean concentrations of copper in plasma had increased and the mean concentration of copper in liver was significantly greater than in undosed control steers (14.1 +/- 4.8 mg copper/kg fresh weight liver in dosed steers, 4.7 +/- 1.4 mg copper/kg in control steers) and was similar to the concentration in steers which had received 200 mg copper as copper calcium edetate (18.2 +/- 4.2 mg copper/kg fresh weight). In sheep the minimum rate of release of copper into the reticulorumen was 2.1 mg/day and in steers 11 mg/day.

Effects of selenium and copper supplementation on the growth of beef steers.

During the grazing seasons of 1978 and 1979, 126 Hereford cross Friesian and 25 Charolais cross Friesian steers were used in controlled trials of the effects of injecting them with copper and, or, selenium. In both seasons the unsupplemented steers had low blood concentrations of copper, selenium and glutathione peroxidase, whereas the supplemented steers maintained their serum copper concentrations within the normal range and had significantly higher whole blood concentrations of selenium and glutathione peroxidase than the unsupplemented animals. Supplementing the steers with 400 mg copper during 1978 increased their growth rate by 0.032 kg/day and supplementing them with 200 mg copper during 1979 increased it by 0.080 kg/day. Supplementing the steers in each year with two doses of selenium, each of 0.15 mg selenium/kg bodyweight, increased their growth rate by 0.041 kg/day in 1978 and by 0.060 kg/day in 1979. There was no interaction between the selenium and copper treatments and the total increases in liveweight gains due to both supplements were around 11 kg in 1978 and 16 kg in 1979.

A field trial of 1alpha-hydroxycholecalciferol (1alpha-OH D3) in the prevention of milk fever.

The efficacy of 1alpha-OH cholecalciferol for the prevention of milk fever has been tested in a controlled field trial using 597 cows on 19 farms all of which had previously had a high incidence of milk fever. Of 293 cows receiving 1alpha-OH cholecalciferol 34 had milk fever and of 304 control cows 51 had milk fever. Although there was an apparent efficacy of 31 per cent the difference in incidence was not statistically significant. There was no effect if 1alpha-OH cholecalciferol was administered less than 24 hours before the cows succumbed to milk fever. However, if 1alpha-OH cholecalciferol was administered more than 24 hours and less than one week before the occurrence of milk fever the efficacy increased to 61 per cent and the effect was highly significant.

Effect of reduced water intake by lactating dairy cows on behaviour, milk yield and blood composition.

A herd of lactating British Friesian cows was divided into two equal groups. After 14 days during which all the cows had free access to water one group (restricted) was allowed only 50 per cent of the voluntary water intake of the other group (control). After four days when the experiment was terminated, the milk yield of the restricted group had fallen to 74 per cent of that of the control group and their mean body-weight was reduced by 14 per cent. In the restricted group there were significant increases in the concentrations of urea, sodium, total protein and copper in serum, in the osmolality of serum, in the plasma activities of the enzymes creatine kinase and glutamate-oxaloacetate transaminase and in the packed cell volume of blood. The restricted cows behaved very aggressively around their water trough and spent more time in its vicinity. They spent less time lying down than the cows of the control group and some of them were not seen to drink and were withdrawn from the experiment before the end of four days. In a second experiment half the herd was allowed approximately 90 per cent of the water intake of the control group for 14 days. Decreases in milk yield and body-weight and changes in blood composition were much smaller and difficult to detect. However, changes in behaviour were still easily recognised although not as marked as in the first experiment.

Use of 1alpha-OH cholecalciferol in preventing post parturient hypocalcaemia and its potential value for the prevention of milk fever in dairy cows.

Cows which received 250 mug 1alpha-hydroxy cholecalciferol (1alpha-OH D3) intramuscularly within two hours after calving suffered significantly less post-parturinet hypocalcaemia and hypophosphataemia than control cows. There was a small depression in plasma magnesium concentrations in the treated cows. 1alpha-OH D3 shows potential for the prevention or treatment of milk fever.