A comparison of vitamin B12 levels in the livers and sera of sheep measured by microbiological and radioassay methods

Five radioassay methods (commercial kits) were evaluated for the determination of vitamin B₁₂ in sheep serum. They provided results that correlated significantly (P<0.01) with those obtained using a microbiological assay.

One radioassay method was evaluated for analysing vitamin B₁₂ in liver, and the results were in excellent agreement with those obtained by the microbiological method.

Little correlation between serum and liver vitamin B₁₂ levels was found. The limited diagnostic value of serum vitamin B₁₂ concentrations for detecting cobalt deficiency in sheep is discussed.     

The distribution of copper, vitamin B12 and zinc in the livers of sheep

Six livers from one-year-old sheep were each sampled at 27 different sites and the concentrations of copper, vitamin B12 and zinc determined for each sample. The distribution of these components was uniform throughout the liver, indicating that analysis of a single liver biopsy sample would give an accurate assessment of their hepatic concentration.     

The distribution of copper,vitamin B12 and zinc in the livers of sheep

Six livers from one-year-old sheep were each sampled at 27 different sites and the concentrations of copper, vitamin B,, and zinc determined for each sample. The distribution of these components was uniform throughout the liver, indicating that analysis of a single liver biopsy sample would give an accurate assessment of their hepatic concentration.     

Reference curves to diagnose cobalt deficiency in sheep using liver and serum vitamin B12 levels

Reference curves demonstrating the relationship between serum or liver vitamin B12 and weight gain were derived from the examination of 16 published and 48 unpublished N.Z. trials. From these curves probability of obtaining an economic reponse (>10g/day body weight increase) for any serum or liver vitamin B12 can be determined. No significant (P<0.05) weight gain responses occurred to vitamin B12 or cobalt treatment in trials with mean serum vitamin B12 levels above 500 pmol/l or liver vitamin B12 levels greater than 500 nmol/kg. The reference curves were therefore derived from trials with vitamin B12 levels below these levels; 36 trials with serum vitamin B12 and 19 trials with liver vitamin B12 data. The mean vitamin B12 level at the mid point of the weight gain response period was selected from each trial. Examination of serum vitamin B12 reference curves for spring, summer, autumn and winter indicated that curves derived from data closest to the middle of January (summer) adequately reflected response to treatment at any time during the first year of life. Reference curves for liver vitamin B12 also used data closest to middle of January. This was partly because insufficient liver data was available to compare seasonal variations. The fitted response curve approached 0 gram/day at 500 pmol/l for serum vitamin B12 and 375 nmol/kg for liver vitamin B12. The minimum vitamin B12 level at which an economic response to treatment (>10 g/day) is not likely was 336 pmol/l for serum and 282 nmol/kg for liver.     

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.     

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.     

The effect of sporidesmin toxicity on ovine serum vitamin B12 levels

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 micromol/kg) and mean (of 3) liver vitamin B12 levels in the sheep were low (<400 nmol/kg) during the period in which facial eczema occurred. Mean serum vitamin B12 levels of the untreated group were low (<485 pmol/l) 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.     

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.     

Contribution of cobalamin analogues to plasma vitamin B12 concentrations in cattle

Plasma vitamin B12 concentrations in cattle were analysed by a radioisotope dilution assay using pig intrinsic factor and a microbiological assay using Euglena gracilis. Both assays provided similar results for samples of cattle plasma containing vitamin B12 concentrations ranging from 0.07 to 3.60 micrograms litre-1 (r = 0.95, P less than 0.001). The addition of excess cobinamide in the radioisotope dilution assay to block non-specific binding in the intrinsic factor preparation due to the presence of R-type binders, was used to determine the presence of cobalamin analogues. Cobalamin analogues accounted for up to 50 per cent of the total vitamin B12 concentration in samples of plasma from cows but were virtually undetectable in plasma from sheep.     

An evaluation of the efficacy of injectable microencapsulated vitamin B12 in increasing and maintaining the serum and liver vitamin B12 concentrations of lambs

AIM: To develop a long-acting Vitamin B12 injection to prevent Co deficiency in sheep. METHODS: Formulations of microencapsulated Vitamin B12 in lactide-glycolide polymers were injected intramuscularly or subcutaneously into the anterior neck region of groups of 10 lambs and their efficacy determined from changes in serum and liver Vitamin B12 concentrations. RESULTS: The 95:5 lactide glycolide and the 100 lactide formulations containing more than 12.5% Vitamin B12 w/w significantly increased and maintained serum Vitamin B12 concentrations for at least 210 days as well as liver Vitamin B12 concentrations in treated lambs when compared with untreated controls. CONCLUSIONS: Injections of microencapsulated Vitamin B12 in lactide/glycolide copolymers are able to increase and maintain the Vitamin B12 status of lambs for at least 210 days. CLINICAL SIGNIFICANCE: Another option for the prevention of Co deficiency in sheep is now available using a long acting injectable Vitamin B12.     

Survey of the status of copper, interacting minerals, and vitamin E levels in the livers of sheep in Ontario

Livers from cull ewes and market lambs raised in Ontario were obtained to determine the status of specific minerals and vitamin E. Values for copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn) obtained by atomic absorption and inductively coupled plasma--atomic emission spectroscopy (ICP-AES) were found to be statistically different but sufficiently biologically similar to allow the use of ICP-AES for screening groups of samples for deficient or toxic levels of those minerals. Toxic levels of cadmium were not found. Toxic levels of aluminum were found in 1 cull ewe and 1 market lamb. A significant proportion of both market lamb samples (40.0%) and cull ewe samples (50.0%) had high to toxic levels of Cu. In market lambs, Fe, Mn, molybdenum (Mo), selenium (Se), and Zn were not found to be important determinants of Cu level. In cull ewes, Fe, Mn, and Zn play a moderate role in the variability of liver Cu levels. Selenium was found to be present at marginal levels in 3.3% of cull ewe samples and in 42.6% of market lamb samples. Vitamin E was found to be low to deficient in 10.0% of cull ewe samples and in 90.0% of market lamb samples. In market lambs, only Mo was associated with Se levels, and no minerals were associated with vitamin E levels. In cull ewes, there was a strong association between Se and vitamin E. This survey demonstrates that marked nutritional imbalances of Cu, Se, and vitamin E exist in cull ewes and market lambs in Ontario.     

Antibodies to Borrelia spirochetes in sera from Swedish cattle and sheep

In the southern parts of Sweden a Borrelia infection transmitted by the tick Ixodes ricinus may affect man, In the present study antibodies to Borrelia spirochetes were studied in sera from 58 cows, 68 calves and 13 lambs from areas in southern Sweden where Ixodes ricinus occurs. For comparison, serologic studies were also performed on 88 cows and 10 lambs from the northern parts of Sweden.Serum titers of > 80 were found in 14 of the calves and 23 of the cows from southern Sweden but in only 1 of the cows from northern Sweden. In 11 of the lambs from the south a serum titer of > 40 developed. None of the lambs from the north had a serum titer of > 40. The results indicate that cattle and sheep in certain areas of Sweden are exposed to Ixodes ricinus-borne Borrelia spirochetes.In 9 of the lambs from southern Sweden: an endemically occurring arthritis had developed. The possibility that this arthritis may be caused by Borrelia spirochetes is discussed.     

Blood thiamine levels in normal cattle and sheep at pasture

Analysis of whole blood samples from 174 cattle and 174 sheep from 3 geographical regions of New Zealand over a 10 month period showed a mean (range) thiamine level of 122 nmol/l (71–237 nmol/l) for cattle and 118 nmol/l (67–227 nmol/l) for sheep. Regional and seasonal differences were noted with levels tending to rise over the summer period. A reference range of 75–185 nmol/l is proposed for both cattle and sheep to cover these variations. Levels below 50 nmol/l are considered indicative of deficiency.     

Blood thiamine levels in normal cattle and sheep at pasture

Analysis of whole blood samples from 174 cattle and, 174 sheep from 3 geographical regions of New Zealand over a 10 month period showed a mean (range) thiamine level of 122 nmol/l (71-237 nmol/l) for cattle and 118 nmol/l (67-227 nmol/l) for sheep. Regional and seasonal differences were noted with levels tending to rise over the summer period. A reference range of 75-185 nmol/l is proposed for both cattle and sheep to cover these variations. Levels below 50 nmol/l are considered indicative of deficiency.