Case study of copper poisoning in a British dairy herd

Following the initial diagnosis of chronic copper poisoning (CCP), the copper (Cu) status of a British dairy herd was investigated. Eight fatal cases of CCP were identified over a 17-month period, from December 1999 to May 2001, involving seven Jersey cows and one Holstein-Friesian; seven cows were dry when CCP occurred. Case diagnostic criteria were necrotising hepatopathy associated with abnormally high liver and kidney Cu concentrations. Analysis of the ration for the high-yielding Jersey cow group revealed about 50 mg Cu/kg dry matter intake (DMI). Risk factors predisposing to fatal CCP were Jersey breed, previous high yield, first two weeks of the dry period and moderately high dietary Cu (greater than 40 mg Cu/kg DMI).

Lead poisoning in cattle and its implications for food safety

The lead poisoning incidents in cattle investigated by the Veterinary Laboratories Agency between 1990 and 2003 are reviewed. Lead poisoning was most commonly encountered in young calves, but cattle of all ages were affected. The lead was derived mainly from lead paint, lead accumulator batteries and lead in soil from old mine workings. Paint was responsible for the majority of cases of poisoning in young calves; yearling animals were most at risk from discarded batteries, and adult cows were most commonly poisoned by geochemical sources of lead. There was a marked seasonal incidence, with most cases occurring after turnout in the spring and early summer.

An evaluation of the effect of clotting on the relationship between copper and caeruloplasmin in bovine blood

The ratio of caeruloplasmin activity to copper concentration (CP:Cu) has been suggested as a more accurate determinant of the requirement for additional copper than plasma or liver copper concentrations. Although this test has no peer-reviewed evidence of efficacy, it has been used by a large number of UK veterinarians. However, the available test uses a serum caeruloplasmin (sCP) activity to plasma copper (pCu) concentration ratio which, because of the preferential loss of caeruloplasmin during clotting, is likely to underestimate the true CP:Cu, although it has been suggested that the marginal range accounts for this. This study was undertaken to evaluate the effect of using serum copper (sCu) rather than pCu concentrations in calculating CP:Cu. Using sCu rather than pCu increased CP:Cu by more than was accounted for by the marginal range. Of 48 cattle which were reported as 'low' using sCP:pCu, 22 were 'normal' when sCu was used instead of pCu. All herds with 'marginal' or 'low' mean CP:Cu when the sCP:pCu concentration ratio was used had 'normal' ratios when sCu was used instead of pCu.

The assessment of blood copper status in cattle: A comparison of measurements of caeruloplasmin and elemental copper in serum and plasma

AIM

To evaluate the effect of test, either copper (Cu) concentration or caeruloplasmin (CP) activity, and sample type, either serum or plasma, on the diagnosis of blood Cu status in cattle.

METHODS

Paired serum and heparinised plasma samples taken from 125 cattle in 13 herds were tested for Cu concentration and CP activity. The individual results for serum Cu concentration and serum and plasma CP activities were compared with the plasma Cu concentration results, as were their diagnostic values as determined by reference ranges, i.e. 'marginal', 'adequate', 'excess'.

RESULTS

The overall mean serum Cu concentration was 2.92 micromol/L lower than the mean plasma Cu concentration; however, there was significant variability between individual samples, and the 95% limits of agreement ranged from 0.44 micromol/L more to 6.28 micromol/L less. The relationship between CP activity and plasma Cu concentration was less variable; the 95% prediction interval for plasma Cu concentration from CP activity was +/- 2.8 micromol/L, and was unaffected by whether CP activity was measured in plasma or serum. Using the threshold currently recommended for 'marginal' status of <8.0 micromol/L for serum Cu concentration identified a significantly different population of cattle than a threshold of <9.0 micromol/L for plasma samples. Altering the threshold to <7.0 micromol/L for serum Cu concentration produced better agreement. For CP activity, a threshold of 15 IU/L for both serum and plasma identified the same population as a threshold of <9 micromol/L for plasma Cu concentration.

CONCLUSIONS

Serum Cu concentration is not a suitable substitute for plasma Cu concentration for the detection of 'marginal' blood Cu status in cattle as the individual variability in the apparent loss of Cu during clotting is too great. In this study, CP activity, in both serum and plasma, was found to be a suitable substitute for the detection of 'marginal' blood Cu status.

CLINICAL RELEVANCE

The use of serum Cu concentration rather than plasma Cu concentration in the diagnosis of Cu responsive disease in cattle needs to be re-evaluated as does the way in which individual sample results are used in such tests.

An evaluation of the copper sequestrated during clotting in cattle: is it just caeruloplasmin?

In cattle, sequestration of copper (Cu) occurs during the clotting process so that serum Cu concentrations are markedly lower than plasma Cu. It has been suggested that all of the Cu lost during clotting is caeruloplasmin (CP). This study used paired samples from 125 cattle to assess whether this assumption was correct. The regression equations for plasma CP activity against plasma Cu concentration and serum CP against serum Cu had significantly different intercepts suggesting that at zero CP activity the amount of Cu remaining was dependent on sample type. Furthermore, the difference between serum and plasma Cu was unrelated to Cu status, whereas the difference between serum and plasma CP was related to Cu status. The regression equation for the loss of CP activity against change in Cu concentration had an intercept that was different from zero, indicating that a reduction in Cu concentration could occur even if CP activity was unaffected by clotting.

Effects of housing and intake of methionine on the growth and wear of hoof horn and the conformation of the hooves of first-lactation Holstein heifers

This study investigated the effects of housing primiparous lactating Holstein heifers either in cubicles with butyl rubber mats, cubicles with thicker mattresses filled with chopped rubber, or straw yards, and supplementing them with methionine for the first 13 weeks of lactation on the rates of growth of their hoof horn and the conformation of their feet. Overall, the rate of growth of the hoof horn increased significantly after calving but the rate of wear did not increase. In contrast, the type of housing had no significant effect on the growth of the hoof horn, but the heifers in straw yards had significantly lower rates of lateral horn wear. The changes in growth and wear rates resulted in changes in hoof conformation, including the toe angle and the width of the bearing surface, which suggested that heel bulb hypertrophy occurred after the heifers had been moved from soft underfoot conditions on to concrete. Providing 115 per cent of their estimated methionine requirements had no significant effect on the rates of growth and wear of the hoof horn.

Diazinon toxicity in sheep and cattle arising from the misuse of unlicensed and out-of-date products

Two incidents involving the misuse of unlabelled or out-of-date diazinon products are described. In the first incident, 81 of a group of 210 five-month-old lambs died within 12 hours of being dipped with the contents of a partly used tin of 15-year-old sheep dip. Analysis showed that the diazinon had decomposed by hydrolysis into a range of breakdown products, including tetraethyldithiopyrophosphate (sulfotepp) and monothiono-tetraethylpyrophosphate (monothiono-TEPP), which are much more toxic to mammals than diazinon. In the second incident, four yearling bulls were affected within 48 hours of being treated with a liquid that the farmer believed to be a lice treatment but was actually old diazinon sheep dip. Three of the bulls recovered but one died four days after the treatment. Analysis of the dip confirmed the presence of diazinon but in this incident no breakdown products were detected.

An evaluation of the effect of clotting and processing of blood samples on the recovery of copper from bovine blood

The reference ranges for blood copper (Cu) concentration used by SAC and the UK Veterinary Laboratories Agency have been developed for use with plasma only. Copper sequestration into the clot, primarily in the form of caeruloplasmin, means that serum Cu concentrations are significantly lower than plasma Cu concentrations in the same animals. Serum Cu is commonly used as a surrogate for plasma Cu by applying a proportional conversion factor. However the results of these two studies, which involved a total of 104 pairs of serum and Cu samples from 84 Holstein cattle in one herd, suggest that serum Cu concentrations should not be used in this way. First, the reduction in Cu concentration during clotting was unrelated to initial plasma concentration (varying from 8-59%), which suggests that using a proportional conversion factor is incorrect. Secondly, the correlation between plasma and serum Cu concentration, while significant, was relatively low (r2 proportional 0.6), with the individual variation in Cu loss during clotting ranging from 1.5 to 10.8 micromol/L (mean 4.9 micromol/L). Although this study was undertaken using samples from normocupraemic lactating Holstein cattle in one herd, the data strongly suggest that plasma rather than serum Cu should be used to estimate Cu status unless the laboratory used has developed a reliable serum reference range. We also found that factors other than plasma Cu concentration had a significant effect on loss of Cu during the clotting process. However, no significant effect on the loss of Cu during clotting or by varying the incubation/storage time and temperature of bloods prior to clot removal was noted, nor was there any significant effect of age or Cu intake. Furthermore, when the loss of Cu during clotting was examined in the same heifers at two different timepoints, no correlation between the results was found. Further research is required to establish the factors that affect the loss of Cu during clotting.

Surveillance of suspect animal toxicoses with potential food safety implications in England and Wales between 1990 and 2002

The potential chemical contamination incidents investigated by the Veterinary Laboratories Agency (VLA) between 1990 and 2002 are reviewed. Incidents were identified in the course of the VLA's surveillance of food animal disease and further investigations were carried out on behalf of the Food Standards Agency in order to identify and control the contamination of food animals and animal products with chemical hazards. In total 876 incidents were investigated, of which 588 involved the poisoning of cattle with heavy metals. There were 63 incidents involving the exposure of cattle, sheep, pigs and poultry to the accidental misuse of veterinary medicines, pesticides or rodenticides, and 50 incidents involving their exposure to microbiological toxins, particularly botulism.

The Effect of Housing and Methionine Intake on Hoof Horn Hemorrhages in Primiparous Lactating Holstein Cows

This study investigated the effects of housing and nutrition on the development of hoof horn disease (as identified by the appearance of hoof horn hemorrhages) in primiparous lactating Holstein cows. The first objective was to investigate whether replacing butyl rubber mats in cubicles (free stalls) with thicker mattresses filled with chopped rubber would significantly reduce hoof horn hemorrhages, and if this reduction would so affect the level of hoof horn hemorrhages as to make it similar to that observed in primiparous cows in straw yards. The second objective was to investigate the effect of methionine supplementation for the first 13 wk of lactation on the development of such hemorrhages. This study confirmed that both sole and white line hemorrhages increase during early lactation in housed cows, although the pattern of development of white line hemorrhages is not identical to that of sole hemorrhages. Housing primiparous cows in straw yards after calving significantly reduced the development of hoof horn hemorrhages, but replacing cubicle mats with thicker mattresses had no significant effect. Providing 115% of calculated methionine requirements had no significant impact on the development of hoof horn hemorrhages.

Relationship between acute phase proteins and hoof horn haemorrhages in postpartum first-lactation heifers

As part of a study of the development of hoof horn haemorrhages in first-lactation heifers, measurements were made of acute phase reactants to investigate the link between the acute phase response and the development of the haemorrhages. Over a period of two years, blood samples were taken from two separate groups of heifers, weekly in the three weeks before they calved and then twice weekly until eight weeks after calving. Plasma total protein, albumin, fibrinogen, haptoglobin, seromucoid and serum iron and caeruloplasmin were measured and the relationships between the peak concentration (or activity) or the area under the curve of each acute phase reactant and the peak scores for sole or white line haemorrhages were assessed by linear regression. The results suggested that the development of the hoof horn haemorrhages observed in the study was not accompanied by an acute phase response, and the haemorrhages were therefore not primarily caused by endotoxicosis. The diets and husbandry systems used were typical of dairy farms in the UK and the results therefore suggest that a significant proportion of hoof horn haemorrhages observed in UK dairy cows may not be caused by endotoxicosis.

An assessment of the risks associated with the use of antibiotic resistance genes in genetically modified plants: report of the Working Party of the British Society for Antimicrobial Chemotherapy

Development of genetically modified (GM) plants is contentious, in part because bacterial antibiotic resistance (AR) genes are used in their construction and often become part of the plant genome. This arouses concern that cultivation of GM plants might provide a reservoir of AR genes that could power the evolution of new drug-resistant bacteria. We have considered bacterial DNA transfer systems (conjugation, transduction and transformation) and mechanisms of recombination (homologous recombination, transposition, site-specific recombination and DNA repair) that together might productively transfer AR genes from GM plants to bacterial cells, but are unable to identify a credible scenario whereby new drug-resistant bacteria would be created. However, we cannot entirely rule out the possibility of rare transfer events that involve novel mechanisms. Hence, we also considered if occasional transfers of AR genes (bla(TEM), aph(3'), aadA) from GM plants into bacteria would pose a threat to public health. These AR genes are common in many bacteria and each is found on mobile genetic elements that have moved extensively between DNA molecules and bacterial cells. This gene mobility has already severely compromised clinical use of antibiotics to which resistance is conferred. Accordingly, the argument that occasional transfer of these particular resistance genes from GM plants to bacteria would pose an unacceptable risk to human or animal health has little substance. We conclude that the risk of transfer of AR genes from GM plants to bacteria is remote, and that the hazard arising from any such gene transfer is, at worst, slight.

Effect of concentrate composition and cubicle bedding on the development of hoof haemorrhages in Holstein heifers after calving

Diseases of the hoof horn are the most common cause of lameness in the UK dairy herd, and diet, particularly starch intake, is commonly implicated in their development. This study assessed whether replacing starch carbohydrate with sugar beet pulp, in a diet containing 50 per cent of the dry matter as forage, would significantly reduce the development of hoof horn haemorrhages in dairy heifers after calving. It also investigated the effect of replacing wood shavings as cubicle bedding with chopped straw. The heifers fed the high-fibre diet had a significantly lower yield of milk protein and a significantly higher yield of milk fat than the heifers fed the high-starch diet, indicating that the change of diet had affected rumen fermentation. However, the change had no significant effect on the development of hoof horn haemorrhages. The change of bedding material also had no significant effect on the development of hoof horn haemorrhages.

Hock injuries in cattle kept in straw yards or cubicles with rubber mats or mattresses

Hock damage is one of the most common traumatic injuries suffered by dairy cows, but most hock injuries should be avoidable. This study investigated the effect of housing system on the development of hock damage in first lactation Holstein heifers. After calving, 60 heifers were randomly allocated to either straw yards, cubicles with butyl rubber mats or cubicles with mattresses filled with chopped tyres. The hocks of these heifers were examined in the first week after calving (week 1) and in weeks 6, 12 and 26 of lactation. Hock damage was scored as either 1 (hair loss only) or 2 (all other damage). Heifers housed in cubicles with mats had significantly worse lesions at week 26 than at week 1, while there was no change in heifers housed in cubicles with matresses, and heifers housed on straw had significantly lower lesion scores. Additionally, heifers with no lesions at calving were significantly more likely to develop lesions when kept on mats than heifers kept on straw or mattresses. These data suggest that replacing mats with mattresses in cubicles can result in a significant reduction in traumatic hock injury.

Suspected botulism in dairy cows and its implications for the safety of human food

A large outbreak of suspected botulism occurred on a dairy farm. The affected animals were listless and showed signs ranging from hindlimb unsteadiness to lateral recumbency, although the most common presentation was sternal recumbency with an apparent hindlimb weakness when stimulated to rise. Postmortem examinations revealed no conclusive gross pathology or histopathology. The affected cattle were found to have neutrophilia and hyperglycaemia with no other consistent haematological or biochemical abnormalities. The combination of clinical signs, disease epidemiology and the ruling out of other differential diagnoses strongly supported a diagnosis of unconfirmed botulism; however, the source of toxin was not demonstrated. Botulism is a severe disease in human beings and there are uncertainties about the pharmacokinetics and pharmacodynamics of Clostridium botulinum toxins. In such circumstances, a precautionary approach to food safety is essential. Restrictions were placed on the movement of livestock and sale of milk from the farm premises until 14 days after the onset of the last clinical case.

A survey of vitamin A concentrations in the liver of food-producing animals

High oral doses of vitamin A have been shown to be teratogenic and accordingly the World Health Organization has recommended that the daily intake for pregnant women should not exceed 3.3 mg. Liver contains high concentrations of this vitamin and consequently it has become necessary to assess its level in the livers of food animals. A survey of fresh, frozen, imported and home-produced retail liver samples from calf (42), ox (121), lamb (228), pig (133) and chicken (125) was carried out between August 1992 and April 1993 using a modified version of the method of Ashoor and Knox (1987) to determine retinol and retinyl esters. Interlaboratory comparison showed no significant difference in results for this method and a method which employed hydrolysis of retinyl esters, and there were significant advantages in specificity, simplicity, cost and quality control. The mean +/- sd total vitamin A concentration calculated as retinol equivalents, for all species surveyed was 139 +/- 96 with a range of 3-1267 mg/kg liver. Mean values for individual species were: calf 188 +/- 125, ox 142 +/- 110, lamb 173 +/- 104, pig 174 +/- 118 and chicken 97 +/- 44 mg/kg liver. No change in the vitamin A concentrations in liver were observed compared with previous surveys in the UK, which suggests that the intake of vitamin A from dietary and supplementary sources by different species has not changed. The data from this survey confirm that liver cannot be recommended as a food for pregnant women.

Poisoning of dairy heifers by mercurous chloride

Mercury poisoning was diagnosed in four dairy heifers, three of which died. The clinical signs were variable and included salivation, excessive thirst, extreme depression and severe diarrhoea. Postmortem examinations revealed inflammation and ulceration of the alimentary tract, pulmonary and cardiac haemorrhages, pallor of the kidney cortices and perirenal oedema. The kidney mercury concentrations were in the range 58 to 91 micrograms/g wet tissue. It is believed that the animals were poisoned by the ingestion of soil contaminated with mercurous chloride.

Polioencephalomalacia associated with the ingestion of ammonium sulphate by sheep and cattle

In the latter part of 1991 an unusual neurological disease was recognised on several farms in England. This report describes the case histories and clinical, biochemical and pathological findings in six calves and two lambs aged from two to 44 weeks obtained from five of these farms. Laminar cerebrocortical necrosis and severe bilateral necrosis of the thalamus and/or striatum progressing to cavitation were recognised in their brains. These changes are similar to those of experimental sulphate toxicity. Morbidity rates of 16 to 48 per cent and mortality rates of 0 to 8 per cent were recorded. The affected animals did not respond to vitamin B1 treatment; the erythrocyte transketolase levels of in-contact cattle and of one untreated affected calf and one untreated lamb were within the normal range. All five farms had recently introduced a proprietary concentrate ration containing ammonium bicarbonate. After this ration was withdrawn no new cases of nervous clinical disease were observed. It is suggested that, in at least some cases, the morphology and topography of lesions may distinguish sulphate induced polioencephalomalacia from that of sporadic thiamine-dependent cerebrocortical necrosis.

Nutritional influences on laminitis, sole ulcer and bruised sole in Friesian cows

The effect of feeding a low fibre, high starch diet in early lactation on the incidence of laminitis and sole ulcers in Friesian dairy cows was studied. After calving the herd had been divided and fed one of two diets. Cows fed the low fibre, high starch ration had a 68 per cent incidence of clinical laminitis and a 64 per cent incidence of sole ulcers. Cows fed the higher fibre diet had only 8 per cent clinical laminitis and 8 per cent sole ulcers. The implications of these findings are discussed.