A review of tissue reference values used to assess the trace element status of farmed red deer (Cervus elaphus)

AIMS: This paper reviews the principles for the establishment of biochemical reference criteria for assessing the trace element status of farmed livestock and summarises data for copper, selenium, vitamin B12 and iodine for farmed red deer. COPPER: Enzootic ataxia and osteochondrosis occur when liver copper concentrations are below 60 micromol/kg fresh tissue, and serum copper concentrations are below 3-4 micromol/l. Growth responses to copper supplementation have been equivocal when blood copper concentrations were 3-4 micromol/l, but were significant when mean blood copper concentrations were 0.9-4.0 micromol/l. No antler growth or bodyweight response to copper supplementation was observed when blood ferroxidase levels averaged 10-23 IU/l (equivalent to serum copper concentrations of 6-13 micromol/l) and liver copper concentrations averaged 98 mumol/kg fresh tissue. These data suggest that 'deficient', 'marginal' and 'adequate' ranges for serum copper concentrations should be 5, 5-8, and 8 micromol/l, respectively, and those for liver copper concentrations should be 60, 60-100, and 100 micromol/kg, respectively. SELENIUM: White muscle disease has been reported in young deer with blood and liver selenium concentrations of 84-140 nmol/l and 240-500 nmol/kg fresh tissue, respectively. No growth-rate response to selenium supplementation occurred in rising 1-year-old deer when blood selenium concentrations were less than 130 nmol/l, the range in which a growth-rate response would be expected in sheep. VITAMIN B12: Vitamin B12 concentrations in deer are frequently below 185 pmol/l without clinical or subclinical effects. No growth response was observed in young deer with vitamin B12 concentrations as low as 75-83 pmol/l. A growth response to cobalt/vitamin B12 supplementation occurs in lambs with serum vitamin B12 concentrations 336 pmol/l. CONCLUSIONS: Data that can be used to establish reference ranges for assessing trace element status in deer are limited. More robust reference values for farmed red deer need to be established through further studies relating biochemical data to health and performance.     

Ovine white-liver disease (OWLD). Vitamin B12 and methyl malonic acid (MMA) estimations in blood

At pasture outlet, mean plasma vitamin B12 varied between 210 and 1,200 pmol/l in 1 month old lambs, 19% of them had values below 250 pmol/l. In those put on OWLD pastures, mean values dropped after 2-4 weeks, and mostly stayed below 150 pmol/l throughout grazing. Plasma methylmalonic acid (MMA) rose above 5 mumol/l 2-8 weeks after outlet, and above 15 mumol/l 4 weeks later. Reduced growth occurred 3-8 weeks after plasma B12 dropped below 150 pmol/l, and 4-6 weeks after MMA rose above 5 mumol/l. Clinical OWLD was most often associated with plasma B12 less than 150 pmol/l and MMA greater than 15 mumol/l. Cobalt fertilization of pastures induced satisfactory plasma B12/MMA values for 3 succeeding years. Elevated plasma B12 was found 3 weeks after Co pellet dosing. The use of Co lick resulted in large individual variations in plasma B12/MMA. The control lambs, which were healthy and grew well on pastures which some years contained marginal/deficient cobalt, had plasma B12/MMA values which varied considerably. One year values indicated functional Co deficiency, but none developed OWLD, and growth was satisfactory, but less than other years. In these lambs, high MMA was not always associated with low B12, or depressed growth. OWLD occurred in Co/B12 deficient lambs, but Co/B12 deficient lambs on other pastures did not develop OWLD.     

Concurrent changes in serum vitamin B12 and methylmalonic acid during cobalt or vitamin B12 supplementation of lambs while suckling and after weaning on properties in the South Island of New Zealand considered to be cobalt-deficient

AIM: To compare serum analyses of vitamin B12 and methylmalonic acid (MMA) as indices of cobalt/vitamin B12 deficiency in lambs around weaning. METHODS: Lambs on five properties, considered to be cobalt- deficient, were supplemented with either cobalt bullets, or short- or long-acting vitamin B12 preparations. Blood samples, and in some cases liver biopsies, and liveweights were obtained at monthly intervals. Serum samples were assayed for vitamin B12 and MMA and liver for vitamin B12 concentrations. Pasture cobalt concentrations were measured on three of the properties. RESULTS: Pasture cobalt concentrations were generally maintained below 0.07 microg/g dry matter (DM) on the properties sampled. Growth responses to supplementation were observed on only 2/5 properties, despite serum vitamin B12 concentrations being within the currently used 'marginal' reference range (336-499 pmol/L) for at least 3 months on all properties and in the deficient reference range (0-335 pmol/L) for at least 2 months on all farms except one. Serum MMA concentrations in supplemented lambs were <2 micromol/L, except in those animals sampled 1 month after receiving treatment with a short-acting vitamin B12 injection. Serum MMA concentrations in unsupplemented animals on properties on which no growth response to supplementation occurred generally reached peak levels of between 4 and 7 micromol/L at the nadir of serum vitamin B12 concentration. When a growth response was observed, differences in weight gain between supplemented and unsupplemented lambs occurred as mean serum MMA concentrations increased from 9 to 14 micromol/L. On one property where supplementation commenced before weaning, normal growth rates were maintained despite serum vitamin B12 concentrations of 140 pmol/L and serum MMA concentrations in excess of 40 micromol/L serum. CONCLUSIONS: The possibility that current serum vitamin B12 references ranges for diagnosis of cobalt deficiency are set too high and lead to over-diagnosis of responsiveness to cobalt/ vitamin B12 supplementation is discussed. The suggestion is made that serum MMA concentrations in excess of 9-14 micromol/L will provide a more reliable diagnostic test for cobalt deficiency. However, there was sufficient variation between properties in the relationships between cobalt concentrations of pasture and serum vitamin B12 or MMA concentrations to require more rigorous testing of the reliability of using serum MMA concentration for this purpose. The possibility that differences in rumen fermentation and therefore propionate and vitamin B12 production could be involved is discussed. The measurement of serum MMA and vitamin B12 appears to be of little value whilst the lamb is still suckling. CLINICAL SIGNIFICANCE: Serum MMA concentration may offer advantages over serum vitamin B12 concentrations in the diagnosis of a cobalt/vitamin B12 responsiveness in weaned lambs.     

Trace elements in grass, cattle liver and sheep liver from districts surrounding Karatina, Kenya. II. Copper, molybdenum, zinc and sulphur

Thirty-one samples of pasture grass from districts surrounding Karatina, Kenya were analysed for contents of copper, molybdenum, zinc and sulphur. The following mean values and standard deviations were found: Copper: 8.2 +/- 5.0 mg/kg DM; molybdenum: 1.4 +/- 2.6 mg/kg DM; zinc: 33 +/- 10 mg/kg DM and sulphur: 0.17 +/- 0.06% DM. Mean value of the ratio between copper and molybdenum was 13 +/- 11. Samples of cattle liver (n = 96) and sheep liver (n = 93) were analysed for copper and zinc with the following results: Cattle liver: 21 +/- 16 mg Cu/kg WW and 37 +/- 11 mg Zn/kg WW. Sheep liver: 59 +/- 37 mg Cu/kg WW and 30 +/- 6.4 mg Zn/kg WW. It is concluded that subclinical copper deficiency may occur in cattle in the districts included in the investigation. The copper status of sheep seems to be adequate. The levels of zinc may indicate a marginal intake of this element in sheep.     

A critical evaluation of serum methylmalonic acid and vitamin B12 for the assessment of cobalt deficiency of growing lambs in New Zealand

AIM: To derive reference ranges for serum methylmalonic acid (MMA) for the diagnosis of cobalt/vitamin B12-responsiveness in lambs and critique existing serum vitamin B12 reference ranges. METHODS: Individual animal data from earlier supplementation trials, involving 225 ewes, 106 suckling lambs, 301 lambs during the suckling and post-weaning periods and 414 weaned lambs, for which weight gain to supplementation was observed, were used to derive relationships between serum vitamin B12 and MMA, and liveweight gain. RESULTS: Serum MMA concentrations were rarely elevated above the norm of <2 micromol/L when serum vitamin B12 concentrations were >375 pmol/L, and not elevated into the range where a liveweight response to supplementation occurred (>10 micromol/L) unless serum vitamin B12 concentrations were below 200 pmol/L. Suckling lambs were able to maintain high growth rates despite elevated serum MMA concentrations (>20 micromol/L). CONCLUSIONS: The current reference ranges used in New Zealand for serum vitamin B12 are set conservatively high. Serum MMA concentrations appear to allow better differentiation of a responsive condition than vitamin B12 concentrations. Serum MMA concentrations >13 micromol/L indicate responsiveness to supplementation whilst concentrations <7 micromol/L indicate unresponsiveness. In the range 7-13 micromol/L, variation in response was observed and predictability of response is less certain, but supplementation is advisable. CLINICAL RELEVANCE: The current reference ranges for vitamin B12 responsiveness are conservatively high and lead to over-diagnosis of vitamin B12 deficiency in ill-thriftiness of sheep.     

Trace element metabolism, dietary requirements, diagnosis and prevention of deficiencies in deer

The first deer farms were established in New Zealand about 30 years ago. Extensive studies on trace elements in sheep and cattle have resulted in clarification of the requirements of those species and the development of protocols to diagnose and prevent deficiencies. In contrast, there have been very few studies conducted with deer. This review summarises information available on trace element nutrition of deer and concludes that, in New Zealand, cobalt (Co), vitamin B12, selenium (Se) and iodine (I) deficiencies are of lesser importance than copper (Cu), which can have a significant impact on deer health and performance. However, on individual farms, Se and I deficiency may cause significant production losses if not managed appropriately. There are no reports of production limitations caused by Co deficiency. Copper deficiency manifests itself as clinical disease, namely enzootic ataxia and osteochondrosis. Growth responses to Cu supplementation have only been reported in 2/11 trials and were not predicted from low serum and/or liver Cu concentrations. On the basis of clinical signs of Cu deficiency, the proposed reference ranges used to predict Cu status from serum Cu concentrations (micromol/l) are: 5, deficient; 5-8, marginal and; 8, adequate; and for liver Cu concentrations (micromol/kg fresh tissue) are: 60, deficient; 60-100, marginal and; 100, adequate. Copper supplementation strategies based on Cu-EDTA injections, Cu-oxide needles or the application of Cu to pasture are effective at increasing Cu status for varying periods. More recent research suggests that alternative forage species that have a high Cu content (10 mg/kg dry matter (DM), may play a role in the prevention of Cu deficiency.     

A comparison of vitamin B12 levels in the liver and serum of sheep receiving treatments used to correct cobalt deficiency

The efficacies of four methods, used for the prophylaxis of cobalt deficiency in sheep as measured by the elevation of liver and serum vitamin B12 levels, were compared in marginally deficient sheep over 14 weeks. The methods used were weekly drenches of either cobalt sulphate or cobalt chelate (EDTA) three-weekly injections of hydroxocobalamin, and ruminal cobalt pellets. On the basis of elevated liver and serum vitamin B12 levels, chelated cobalt was shown to be available to rumen microflora for the synthesis of vitamin B12. However, at no stage were liver and serum vitamin B12 levels of sheep receiving the chelate significantly different from those receiving the same amount of cobalt as the sulphate. After five, three-weekly injections of hydroxocabalamin liver vitamin B12 levels were significantly higher (p<0.01) than for the other treatments, with the exception of cobalt sulphate. Cobalt pellets led to an initial rapid and significant rise in serum vitamin B12 when compared with the other treatments. However, at four weeks there was no significant difference between treatment groups for serum vitamin B12. Fourteen weeks after the administration of cobalt pellets, serum and liver.vitamin B12 levels in this group were not significantly different from those of untreated sheep. At this time, three out of 12 sheep had lost their pellets.     

Serum copper concentrations in beef cows and heifers

OBJECTIVE: To characterize serum copper status of cows and heifers in beef cow-calf herds throughout the United States and to evaluate use of copper supplements in those herds. DESIGN: Cross-sectional survey. ANIMALS: 2,007 cows and heifers from 256 herds in 18 states. PROCEDURES: Producers participating in a health and management survey conducted as part of the National Animal Health Monitoring System voluntarily allowed serum samples to be obtained from cows and heifers for determination of copper concentration. Results were categorized as deficient, marginally deficient, or adequate. The proportion of cattle and herds (on the basis of mean value of the tested cattle) in each category was determined. Copper concentrations were compared between herds that reportedly used copper supplements and those that did not. RESULTS: Overall, 34 of 2,007 (1.7%) cows and heifers were deficient in copper, and 781 (38.9%) were marginally deficient. In each region, at least a third of the cattle were deficient or marginally deficient. For herds, 92 of 256 (35.9%) were marginally deficient, and 22 (0.8%) were deficient. Approximately half of the producers reported use of copper supplements, but a sizeable proportion of those producers' cattle and herds were classified as marginally deficient or deficient. CONCLUSIONS AND CLINICAL RELEVANCE: Copper deficiency is not restricted to a single geographic region of the United States. Copper deficiency can persist despite reported use of supplements by producers. Veterinarians dealing with beef cow-calf herds that have problems consistent with copper deficiency should not rule out copper deficiency solely on the basis of geographic region or reported use of copper supplements for the herd.     

White liver disease in goats

Three field cases of ill-thrift, hepatic lipodystrophy and low tissue levels of vitamin B12 in young angora cross goats are reported. The cases meet the criteria for the diagnosis of white liver disease (WLD) described for sheep. The hypothesis that WLD is a metabolic consequence of cobalt/vit B12 deficiency in sheep and goats on a diet rich in propionate is developed, together with possible reasons for its occurrence in these species but not in cattle or red deer.     

A comparison of serum vitamin B12 and serum methylmalonic acid as diagnostic measures of cobalt status in cattle

In two trials an assessment was made of serum methylmalonic acid as a diagnostic criterion of cobalt status in housed cattle. Despite the small number of animals used the method showed some promise, and normal concentrations are tentatively suggested as being less than 2 mumole/litre, subclinically cobalt deficient 2 to 4 mumole/litre and cobalt-deficient greater than 4 mumole/litre. However, for assessing how cobalt status is likely to influence the rate of liveweight gain of cattle, measurements of both serum methylmalonic acid and vitamin B12 concentrations would appear to be better.     

Parenteral administration of copper as cerate to cattle and sheep

Extract

Under the grassland farming regime in New Zealand, copper deficiency in cattle and sheep can be effectively controlled by topdressing all the pastures on the farm each year with 5 pounds of copper sulphate per acre. Such treatment removes the deficiency by increasing the copper content of the herbage to a level that is adequate for grazing animals.     

Reduction of the prevalence of footrot on New Zealand farms by vaccination

AIM: To compare serum analyses of vitamin B₁₂ and methylmalonic acid (MMA) as indices of cobalt/vitamin B₁₂ deficiency in lambs around weaning.

METHODS: Lambs on five properties, considered to be cobalt- deficient, were supplemented with either cobalt bullets, or short- or long-acting vitamin B₁₂ preparations. Blood samples, and in some cases liver biopsies, and liveweights were obtained at monthly intervals. Serum samples were assayed for vitamin B₁₂ and MMA and liver for vitamin B₁₂ concentrations. Pasture cobalt concentrations were measured on three of the properties.

RESULTS: Pasture cobalt concentrations were generally maintained below 0.07 μg/g dry matter (DM) on the properties sampled. Growth responses to supplementation were observed on only 2/5 properties, despite serum vitamin B12 concentrations being within the currently used ’marginal‘ reference range (336–499 pmol/L) for at least 3 months on all properties and in the deficient reference range (0–335 pmol/L) for at least 2 months on all farms except one. Serum MMA concentrations in supplemented lambs were <2 μmol/L, except in those animals sampled 1 month after receiving treatment with a short-acting vitamin B12 injection. Serum MMA concentrations in unsupplemented animals on properties on which no growth response to supplementation occurred generally reached peak levels of between 4 and 7 μmol/L at the nadir of serum vitamin B12 concentration. When a growth response was observed, differences in weight gain between supplemented and unsupplemented lambs occurred as mean serum MMA concentrations increased from 9 to 14 μmol/L. On one property where supplementation commenced before weaning, normal growth rates were maintained despite serum vitamin B12 concentrations of 140 pmol/L and serum MMA concentrations in excess of 40 μmol/L serum.

CONCLUSIONS: The possibility that current serum vitamin B₁₂ references ranges for diagnosis of cobalt deficiency are set too high and lead to over-diagnosis of responsiveness to cobalt/ vitamin B₁₂ supplementation is discussed. The suggestion is made that serum MMA concentrations in excess of 9–14 μmol/L will provide a more reliable diagnostic test for cobalt deficiency. However, there was sufficient variation between properties in the relationships between cobalt concentrations of pasture and serum vitamin B₁₂ or MMA concentrations to require more rigorous testing of the reliability of using serum MMA concentration for this purpose. The possibility that differences in rumen fermentation and therefore propionate and vitamin B₁₂ production could be involved is discussed. The measurement of serum MMA and vitamin B₁₂ appears to be of little value whilst the lamb is still suckling.

CLINICAL SIGNIFICANCE: Serum MMA concentration may offer advantages over serum vitamin B₁₂ concentrations in the diagnosis of a cobalt/vitamin B₁₂ responsiveness in weaned lambs.     

Measurement of vitamin B12 in the livers and sera of sheep and cattle and an investigation of factors influencing serum vitamin B12 levels in sheep

Modifications of a radioassay method for the analysis of vitamin B12 using chicken serum as the binder are described. This obviates the need to use individual serum blanks to correct for non-specific binding in vitamin B12 assays of the sera and livers of sheep and cattle. Samples with high vitamin B12 levels can be diluted prior to assay without loss of linearity. Recoveries of added cyanocobalamin or hydroxocobalamin were better than 95% and results correlated significantly with those obtained using a microbiological assay (Poteriochromonas malhamensis). Sera and liver samples stored for four weeks at temperatures ranging from -20 degrees to 22 degrees showed no change in vitamin B12 levels. Withholding food from sheep for 44 hours led to a marked increase in serum vitamin B12. This effect was also evident in sheep eating a limited amount of cut grass. In sheep at pasture there was no evidence of a diurnal variation in serum vitamin B12 levels. Serum vitamin B12 levels in sheep at pasture were shown to be an unreliable indicator of liver vitamin B12.     

The effect of copper deficiency on the peripheral blood cells of cattle

Six female cattle were given molybdenum (30 ppm) and sulphate (225 ppm) to induce experimental secondary copper deficiency. The total and differential leukocyte numbers and lymphocyte subpopulations were counted and the neutrophil activity was assessed by means of nitroblue tetrazolium reduction and phagocytosis of sheep erythrocytes. The serum caeruloplasmin activity and concentration were also determined. Copper deficiency was confirmed from decreased serum copper levels, the animals with values less than 5.9 µmol/L being considered deficient. Total leukocyte numbers were not affected by the copper deficiency. However, differential counts showed a marked increase in monocyte subpopulations, a significant decrease in B lymphocytes and reduced neutrophil activity. The serum caeruloplasmin activity was decreased about 50%, but the total serum protein concentration was less altered. We concluded that the effect of these changes on the animals' immune competence may contribute to a greater incidence of infectious diseases in copper-deficient cattle.     

The retention and efficacy of soluble-glass boluses for providing selenium, cobalt and copper to sheep

The efficacy and retention of prototype and commercial (Cosecure) soluble-glass boluses containing selenium, cobalt and copper and having a similar size, density and composition were evaluated in separate 12-month trials with sheep grazing low selenium pastures but with adequate cobalt and copper levels. In both trials, sheep confirmed by X-ray as containing a bolus grew at a significantly greater rate than control sheep. This was attributed to the correction of a selenium deficiency. Although liver copper, and liver and serum vitamin B12 levels were significantly greater in treated sheep than controls on some occasions, the differences were not as great or consistent as with blood selenium levels. The rate of bolus loss was high and in both trials, approximately 40% of the sheep had lost the bolus after 6 months. No prototype boluses were present after 12 months. Intact Cosecure boluses were recovered from 3 sheep out of 30 after 12 months whilst one animal contained a part bolus. The recovered boluses were approximately 45% lighter than when originally administered. Bolus loss did not appear to be due to complete dissolution. In sheep which had lost the bolus, blood selenium levels fell with a half-life of 43 +/- 10 days.     

The effectiveness of oral and parenteral vitamin A doses in growing cattle with different vitamin A supplies]

The effect of one single oral or parenterally administered dose of 1 million IU vitamin A on the vitamin A depot in the liver and on blood plasma vitamin A concentrations was investigated in 3 individual feeding experiments with involvement of 18 and 24 calves or 24 fattening bulls. 50% of all animals in each of the 3 experiments received feed without any vitamin A through 108 or 112 or 209 days, prior to vitamin A administration, or received 10.000 IU/100 kg live weight and day. Parenteral vitamin A administration in either group yielded rise in blood plasma from 0.06--0.35 to 26.2--30.2 mumol/l, after 1 or 2 days. The maximum value measured after oral administration was 1.9 mumol/l. Most of the plasma values had returned to normal (0.6--12. mumol/l) within 14 days from administration. Oral and parenteral vitamin A doses, after 14 days, caused significant rise in vitamin A concentrations in the liver (from 15.5 to 82.5), with the increase resulting from parenteral administration (from 13.7 to 99.1) being clearly higher than that resulting from oral administration (from 17.3 to 65.9 mumol/kg fresh liver tissue). The same trends were recorded from recovery of vitamin A from the liver (26.8% after parenteral administration versus 15.0% in the wake of oral doses). Storage in and recovery from vitamin-A depleted animals were below values recorded from young cattle with sufficient vitamin A supply. These findings are likely to confirm that one single parenteral vitamin A administration was of clearly higher effectiveness, as compared to oral application.     

Failure of copper or vitamin D supplements to affect the dental condition of young sheep on two Wairarapa farms

Regular injections of copper or vitamin D had no overall effect on growth rate, fleece weight, or the amount of wear of the central incisor teeth of sheep on two Wairarapa farms over 26 months. The greatest amount of tooth wear occurred during the period when soil ingestion (measured by acid-insoluble residue, titanium or aluminium in the faeces) was also greatest. Various indicators of copper, calcium or nutritional status were measured in the blood of control sheep and those receiving vitamin D or copper. At no sampling time was there a significant difference for any of these between groups on either farm. Pasture samples were analysed regularly for calcium, cobalt, copper, magnesium, manganese, molybdenum, phosphorus, sulphur, zinc and percentage ash. At most times values were, on the basis of existing criteria, considered normal. Although the pasture calcium/phosphorus ratio fell below one on several occasions this did not result in a change in plasma calcium or phosphorus levels. On the basis of criteria established for pen-fed sheep, dietary available copper levels on both farms were considered low for much of the time. However, liver and blood copper values were adequate at alI times.     

The vitamin A requirement and the vitamin A status of growing cattle. 1. Studies of calves

Five experiments with 18 to 36 male calves each of the black and white dairy cattle breed (age: 14-21 days, initial live weight: approximately 45 kg per animal) were carried out in order to investigate the influence of various vitamin A supply (0-80,000 IU per 100 kg LW and day) on dry matter intake and weight gain as well as the vitamin A status of liver and blood plasma over 84 days. The calves consumed a diet free of carotene and vitamin A consisting of milk replacer, concentrate and chopped wheat straw. The calves were fed in three experiments for a longer time in order to observe the further vitamin A depletion. Nine animals consumed an unsupplemented ration, nine other one got 10,000 IU vitamin A per 100 kg LW and day. Biopsies of liver and plasma samples were taken from 4 animals per group every four weeks. The various vitamin A supplementation did not significantly influence the dry matter intake (Mean: 1.67; 1.48 to 1.80 kg DM per animal and day) and the weight gain of calves (Mean: 702, 599 to 770 g per animal and day). First vitamin A deficiency symptoms (reduced feed intake, decreased weight gain, diarrhoea etc.) were observed in animals of unsupplemented group after 100 days of experiments. After 84 days the vitamin A concentration of liver of animals of unsupplemented groups decreased to 1.3-32.2% compared with the begin of experiments (60.6-155.7 mumol/kg fresh matter). Up to 51% of initial concentration were found when 10,000 IU vitamin A per 100 kg LW and day were fed. About 25,000 IU vitamin A per 100 kg LW and day were required in order to keep the initial level of vitamin A concentration of liver. The plasma vitamin A concentration is unsuitable for estimation of vitamin A status of calves. The concentration of vitamin A of liver and plasma amounted to 114 mumol per kg and 0.25 mumol per litre at the begin of experiments. The vitamin A concentration of liver of unsupplemented group decreased to 20 mumol per kg, that of plasma increased to 0.28 mumol per 1 at the end. A strong vitamin A deficiency (liver concentration: less than 10 mumol/kg) may cause a decrease of vitamin A concentration of blood.     

The occurrence of Anthrax in New Zealand

A field outbreak of facial eczema occurred during a vitamin B12 response trial in young growing sheep. Pasture cobalt levels were in the low range for sheep <0.08 mg/kg, 1.358 µmol/kg) and mean (of 3) liver vitamin B12 levels in the sheep were low (>100 nmol/kg) during the period in which facial eczema occurred.

Mean serum vitamin B12 levels of the untreated group were low (>185 pmol/1) for the two months (January and February) preceding the period of facial eczema. However, levels showed an approximate 3.5 fold increase in both cobalt supplemented and unsupplemented groups with the onset of facial eczema in March. From February to March the mean serum vitamin B12 and glutamyl transferase (GGT) activity showed parallel increases with a positive correlation (r = 0.73) between log serum vitamin B12 and log serum GGT activity during the period January to July for both groups. This finding suggested that the increase in serum vitamin B12 was due to sporidesmin induced liver damage.

The diagnostic implication is that, in areas where facial eczema is a problem, liver is the sample of choice for determining vitamin B12 status, because sporidesmin toxicity can elevate low serum vitamin B12 levels to diagnostically normal levels.     

Absence of a weight gain response to Vitamin B12 supplementation in weaned dairy heifers grazing pastures of marginal cobalt content

AIM: To obtain information on serum and liver vitamin B12 and urinary methylmalonic acid concentrations as diagnostic tests to predict a weight gain response to supplementation with vitamin B12 in young dairy cattle when grazing pasture of low cobalt content. Methodology. Forty dairy cattle (12 Friesian, 14 Friesian x Jersey and 14 Jersey) were allocated to two equal sized groups, treated and untreated, based on liveweight. At monthly intervals for 14 months, all animals were weighed, their serum and urine sampled, their liver biopsied and the pasture sampled from the paddocks they were grazing and going to graze. Serum and liver were assayed for vitamin B12 concentrations. For the first 5 months of the trial, urine was assayed for methylmalonic acid concentrations. Both washed and unwashed pasture samples were assayed for cobalt concentrations. RESULTS: No weight gain response occurred vitamin B12 supplementation in young growing cattle grazing pasture with a cobalt concentration of 0.04-0.06 mg/kg DM. For 5 months of the trial, liver vitamin B12 concentrations from untreated calves were in the range 75-220 nmol/kg and serum vitamin B12 concentrations were as low as 72 pmol/1. There was no associated growth response to supplementation. CONCLUSION: Further trials involving young cattle grazing pastures with cobalt concentrations less than 0.04 mg/kg DM are required to reliably determine liver and serum vitamin B12 concentrations at which growth responses to vitamin B12 or cobalt supplementation are likely under New Zealand pastoral grazing conditions.