An investigation into possible causes of decreased milk production and increased mortality rate in a closed herd of 400 mixed-breed dairy goats was initiated following the death of 9 animals within a 1-month period. The producer reported that goats that died had developed anorexia and recumbency approximately 1 week earlier, with signs progressing to neurologic abnormalities (ie, paddling or vocalizing) before death. The herd was vaccinated against Clostridium perfringens types C and D and dewormed with ivermectin each year at the end of lactation. Animals were housed in dry lots and fed alfalfa hay, a custom grain mix, and a loose mineral mix in their pens. Recent changes in herd management included use of a newly formulated loose mineral mix that had been offered in all animal pens for the preceding 9 months. Sources of the alfalfa hay and custom grain mix had been unchanged during the previous 2 years.
The first doe (doe 1) examined was a 3-year-old, lactating, nonpregnant LaMancha goat that was brought to the University of California Veterinary Medical Teaching Hospital because of agalactia and anorexia of 3 days' duration. Abnormal physical examination findings included moderate dehydration, bruxism, ptyalism, obtundation, and cold extremities. Initial diagnostic testing included a CBC and serum biochemical analysis. Initial treatment included IV administration of polyionic fluids and SC administration of thiamine hydrochloride. The doe became comatose and died 3 hours after admission and was submitted to the California Animal Health and Food Safety Laboratory for necropsy and trace mineral analysis of liver and kidney specimens. Gross lesions at necropsy were restricted to the liver, which displayed a nutmeg appearance. Histologically, there was severe, acute, centrilobular and midzonal hepatic necrosis with hemorrhage. Liver copper concentration was 251 ppm (wet weight; reference range, 25 to 150 ppm), and kidney copper concentration was 44.6 ppm (wet weight; reference range, 3 to 6 ppm). A diagnosis of copper toxicosis was made.
A second doe (doe 2) that was found dead on the dairy 3 days after doe 1 died was also submitted to the California Animal Health and Food Safety Laboratory for necropsy. This was a lactating, nonpregnant Nubian goat. A diagnosis of copper toxicosis was also made in this goat on the basis of liver copper concentration (253 ppm), kidney copper concentration (109 ppm), and histologic evidence of hepatic necrosis.
Over the next 2 weeks, 3 additional lactating does (does 3, 4, and 5) were brought to the Veterinary Medical Teaching Hospital with clinical signs similar to those seen in doe 1, and a diagnosis of copper toxicosis was made in all 3. Copper concentrations measured in liver biopsy specimens from 2 of these 3 does were high (Table 1). Liver biopsy was not performed on doe 5 because it was moribund. In this doe, the diagnosis of copper toxicosis was made on the basis of clinical signs, high serum copper concentration, clinicopathologic abnormalities, and the fact that the doe was from a cohort of animals that had already been found to have copper toxicosis.
Selected hematologic and biochemical test results for 4 lactating goats with clinical copper toxicosis.
|Variable||Reference range||Doe No.|
|Serum copper (ppm)||0.8–1.2||4.52||7.6||1.91||3.04|
|Liver copper (ppm)||25–150||251||195||327||ND|
|RBC count (× 106/μL)||11–21||28.5||18.4||18.39||11.36|
|Plasma protein (g/dL)||6.0–7.5||7.5||7.9||7.4||7.6|
|Urea nitrogen (mg/dL)||19–31||54||30||64||23|
ND = Not determined. MCV = Mean corpuscular volume. MCH = Mean corpuscular hemoglobin. AST = Aspartate aminotransferase. GGT = γ-Glutamyltransferase. SDH = Sorbitol dehydrogenase.
Hospitalized does were treated with polyionic fluids as needed. Penicillaminea (50 mg/kg [23 mg/lb], PO, q 24 h), ammonium molybdate (300 mg, PO, q 24 h), and sodium thiosulfate (300 mg, PO, q 24 h) were administered as chelation therapy, and vitamin E (2,000 U, PO, q 24 h) was administered to reverse copper-induced oxidation. Thiamine hydrochloride (10 mg/kg [4.5 mg/ lb], q 12 h) was administered SC because the does were anorectic. Ceftiofur sodium (2 mg/kg [0.9 mg/lb], IV, q 12 h) was administered prophylactically because of the risk of bacterial hepatitis and septicemia.
None of the does treated at the Veterinary Medical Teaching Hospital (ie, does 1, 3, 4, and 5) had evidence of hemolysis (icterus, anemia, or hemolyzed plasma) at the time of initial examination, and urine was grossly normal in the doe in which toxicosis was confirmed at necropsy. However, in the does that were treated, serum aspartate aminotransferase activity, G-glutamyltransferase activity, and total bilirubin concentration were consistently high (Table 1), although there was no clear association between the magnitude of the increases in these analytes and the serum or liver copper concentration.
To identify possible sources of copper exposure in the herd, copper content of samples of hay (12 ppm), water (< 50 ppb), grain (34 ppm), and mineral mix (3,050 ppm) was analyzed. According to the National Research Council,1 the recommended total dietary intake of copper for a lactating dairy doe weighing 70 kg (154 lb) is 61 mg/d. Assuming total dry matter intake of 2.5% of body weight, daily grain intake of 0.91 kg (2 lb [31 mg of copper]), and daily hay intake of 0.84 kg (1.85 lb [10 mg of copper]), then a doe would have been able to ingest only 6 g of the mineral mix (20 mg of copper) before exceeding this daily requirement. The nutritionist working for the mineral mix manufacturer had instructed the dairy owner to withdraw the mineral mix from the pens at the time doe 1 was examined at the Veterinary Medical Teaching Hospital because of safety concerns related to the product, which was labeled for administration to beef cattle on pasture. Previously, a local distributor for the mineral mix had recommended this product to the owner of the goat dairy.
To this point, the only animals with clinical signs of copper toxicosis had been lactating does. To determine whether other animals in the herd were affected, liver biopsy specimens were obtained from 22 juvenile does and submitted for mineral analysis. In addition, serum copper concentration and serum sorbitol dehydrogenase and G-glutamyltransferase activities were measured. For liver biopsy, the does were sedated with diazepam (10 mg, IV) and hair was clipped on the right side of the thorax. The liver was identified with a 5-MHz curvilinear probe in the right 9th to 11th intercostal space. The skin was prepared aseptically and infiltrated with 1.5 mL of 2% lidocaine. A stab incision was made through the skin with a scalpel blade, and a 16-gauge biopsy needleb was used to collect liver samples. At least 2 samples were collected from each doe, and samples were pooled for mineral analysis. The skin incision was closed with a single staple. Animals were treated at the time of biopsy and for 48 hours thereafter with penicillin G procaine (20,000 U/kg [9,090 U/lb], SC, q 12 h). No complications were observed in any of these animals. Samples were delivered frozen to the California Animal Health and Food Safety Laboratory for trace mineral analysis.
Analysis of the liver biopsy specimens revealed that 7 of the 22 juvenile does had liver copper concentrations higher than the upper reference limit and 9 had serum copper concentrations higher than the upper reference limit (Table 2). Three does (does 10, 13, and 14) had high serum and liver copper concentrations. One doe (doe 7) had a high serum sorbitol dehydrogenase activity, and 4 does (does 6, 7, 10, and 16) had high serum γ-glutamyltransferase activities. Of the 4 does with high serum γ-glutamyltransferase activities, only 1 (doe 10) had a high liver copper concentration, although all 4 had high serum copper concentrations. One doe (doe 7) with high serum γ-glutamyltransferase activity and high serum copper concentration had a liver copper concentration within reference limits. Conversely, a doe (doe 14) with hepatic enzyme activities within reference limits had a slightly high serum copper concentration but also had the highest liver copper concentration observed. Overall, there was no consistent relationship between serum hepatic enzyme activities, serum copper concentration, and liver copper concentration in the juvenile does.
Age and selected biochemical values for 13 juvenile goats with subclinical copper toxicosis.
|Variable||Reference range||Doe No.|
|Serum copper (ppm)||0.80–1.20||1.49||1.63||1.07||1.25||1.38||1.02||1.05||1.28||1.21||1.43||1.40||1.14||1.24|
|Liver copper (ppm)||25–150||51||117||260||77||159||177||155||223||280||113||148||195||108|
NA = Not applicable. See Table 1 for remainder of key.
All lactating goats (n = 205) in the herd were treated with penicillamine (50 mg/kg, PO, q 24 h) for 7 days. The dosage was modified from published recommendations for the treatment of sheep2 to accommodate the extensive labor requirement involved. The effectiveness of chelation therapy was assessed by comparing urine copper concentrations in 2 goats receiving penicillamine with concentrations in 2 age- and sex-matched control goats that were not being treated. After administration of 5 doses of penicillamine, urine copper concentrations in the treated goats were 3.54 and 3.23 ppm, whereas urine copper concentrations in the control goats were less than the limit of detection for the assay method used (ie, < 0.05 ppm).
To our knowledge, there are no published meat or milk withdrawal times following penicillamine treatment in lactating goats. After consultation with the California Department of Food and Agriculture, the dairy was banned from selling milk for 21 days after the last treatment with penicillamine.
It has previously been recommended that small ruminants with copper intoxication be provided supplements containing molybdenum or sulfur2,3 because these elements mix with ingested copper in the rumen, forming insoluble, acid-stable copper tetrathiomolybdenate complexes, thus limiting absorption of ingested copper. The addition of molybdenum and sulfur to the diet also increases the concentrations of these minerals in the enterohepatic circulation, providing a means to bind copper being released from liver stores.4 Finally, biliary and fecal copper concentrations are substantially increased in ruminants receiving diets with a high molybdenum concentration.4,5 For these reasons, all animals in the herd were treated with ammonium molybdate (300 mg, PO, q 24 h) and sodium thiosulfate (300 mg, PO, q 24 h) for 3 weeks. Additionally, all goats were administered vitamin E (2,000 U, PO, q 24 h) for 3 weeks to mitigate possible copper-induced oxidative damage. The dosage of vitamin E was extrapolated from dosages recommended for horses with conditions such as degenerative myeloencephalopathy, protozoal myelitis, and cervical vertebral malformation in which oxidative damage may be a concern.6 This dosage was more than 4 times the published recommended daily requirement of 448 U/d for an 80-kg (176-lb) lactating doe.1
Four months later, 2 of the adult does (does 4 and 5) with clinical copper toxicosis and 2 of the juvenile does with subclinical toxicosis (does 13 and 14) were reevaluated at the Veterinary Medical Teaching Hospital. Both of the does with clinical toxicosis had recovered. One of the juvenile does (doe 13) had sentimental value to the dairy owner and had been treated with penicillamine PO for 5 days after results of mineral analysis of a liver biopsy specimen were obtained. This was the only juvenile goat treated with penicillamine. In all 4 goats, serum γ-glutamyltransferase, sorbitol dehydrogenase, and aspartate aminotransferase activities and serum bilirubin concentration were within reference limits. Liver copper concentration was within reference limits in the 3 does that had been treated with penicillamine but was still high in the doe (doe 14) that had not been treated (201 ppm).
Five months after copper toxicosis was initially diagnosed, the herd had an outbreak of infectious disease, with 4% of the herd dying over a 3-month period. Pleuropneumonia, mastitis, and caseous lymphadenitis accounted for the death of 15 animals, 13 of which were lactating does. Liver vitamin E concentration was low in 10 of the 12 goats that underwent necropsy (mean, 1.1 ppm; reference range, > 3 ppm). To increase vitamin E consumption, the grain mix was reformulated with twice the previous vitamin E content.
Cuprimine, Merck & Co, Whitehouse Station, NJ.
Bard Biopty, Bard Access Systems, Salt Lake City, Utah.
National Research Council. Nutrient requirements of small ruminants sheep, goats, cervids, and new world camelids. Washington, DC: National Academies Press, 2007;276–295.
Ross DB. The effect of oral ammonium molybdate and sodium thiosulfate given to lambs with high liver copper concentrations. Res Vet Sci 1970;11:295–297.
Solaiman SG, Maloney MA & Qureshi MA, et al. Effects of high copper supplements on performance, health, plasma copper and enzymes in goats. Small Rumin Res 2001;41:127–139.
Lopez-Alonso M, Crespo A & Miranda M, et al. Assessment of some blood parameters as potential markers of hepatic copper accumulation in cattle. J Vet Diagn Invest 2006;18:71–75.
Humann-Ziehank E, Bickhardt K. Effects of d-penicillamine on urinary copper excretion in high-copper supplemented sheep. J Vet Med 2001;48:537–544.
Gooneratne SR, McCHowell J, Gawthorne JM. Intravenous administration of thiomolybdate for the prevention and treatment of chronic copper poisoning in sheep. Br J Nutr 1981;46:457–467.
Botha CJ, Naude TW & Swan GE, et al. The cupuretic effect of two chelators following copper loading in sheep. Vet Hum Toxicol 1993;35:409–413.