Chronic copper toxicity of ruminants

There has been an active interest in the toxicology of copper since the middle of the 19th century and a review by Davenport (1953) covers the early work on the hazard to man and animals of both the acute and chronic forms. Review material specific to chronic copper poisoning in farm livestock has also been published by Broughton & Hardy (1934), Eden (1940), Todd (1962) and Bull (1964).

The first description of true chronic copper poisoning in farm animals would seem to be that of Mallory (1925) who produced the condition experimentally in sheep. Beijers (1932) described similar symptoms in sheep grazing orchards which had been sprayed with a copper fungicide, and 2 years later Broughton & Hardy (1934) published their detailed experimental investigations showing the dangers of excessive copper intakes to sheep. The similarity between the symptoms described in these reports and those of ‘yellows’ or ‘toxaemic jaundice’ in Australia was recognized (Bull, 1964) and the experiments of Albiston, Bull, Dick & Keast (1940) confirmed that this naturally-occurring condition was of similar origin. The importance of chronic copper poisoning as a nutritional hazard was, therefore, fully established.

Anaerobic potentiation of copper toxicity and some environmental considerations

The toxicity of copper is substantially greater when the metal ions is applied to cells under conditions of anoxia than under aerobic conditions. The increase in toxicity occurs because Cu(II) is reduced to Cu(I) which is stable under anoxia and is more toxic than the oxidized species. This effect has been observed in mammalian cells in tissue culture and in bacteria. Anoxic potentiation of copper toxicity has also been observed in algal, fungal and yeast cells. The reduction of Cu(II) has been demonstrated by electron paramagnetic resonance spectrometry. The appearance of Cu(I) has been observed by means of specific colorimetric reagent. The reduction of Cu(II) to Cu(I) is not dependent upon concomitant metabolism and requires only a supply of sulphydryl groups. Microorganisms that are responsible for two anaerobic processes of economic importance to humans, the digestion of sewage sludge in effluent treatment plants and the digestion of food in ruminant animals, may be exposed to high concentrations of copper. The environmental consequences of this exposure are discussed.

Effects of copper oxide bolus administration or high-level copper supplementation on forage utilization and copper status in beef cattle

Two experiments were conducted to study effects of high-level Cu supplementation on measures of Cu status and forage utilization in beef cattle. In Exp. 1, eight steers randomly received an intraruminal bolus containing 12.5 g of CuO needles (n = 4) or no bolus (n = 4). Steers were individually offered free-choice ground limpograss (Hemarthria altissima) hay. On d 12 (Period 1) and d 33 (Period 2) steers were placed in metabolism crates, and total forage refused and feces produced were collected for 7 d. Daily samples of forage offered and refused and of feces excreted for each steer within period were analyzed for DM, ash, NDF, ADF, and CP. Liver biopsies were collected on d 0, 12, and 33. Copper oxide bolus administration resulted in greater (P < 0.03) liver Cu (DM basis) accumulation in Period 1 (556 vs. 296 mg/kg) and Period 2 (640 vs. 327 ppm). Apparent digestibilities of NDF and CP were greater (P < 0.04) for steers receiving no bolus in Period 2 (62.2 vs. 57.1% and 50.2 vs. 43.4% for NDF and CP digestibility, respectively). In Exp. 2, 24 crossbred heifers were assigned to individual pens and received a molasses-cottonseed meal supplement fortified with 0, 15, 60, or 120 ppm of supplemental Cu (Cu sulfate; six pens per treatment). All heifers were offered free-choice access to ground stargrass (Cynodon spp.) hay. Heifer BW and liver biopsies were collected on d 0, 42, and 84. Forage refusal was determined daily, and diet DM digestibility was estimated over a 21-d period beginning on d 42. Heifers consuming 120 ppm of supplemental Cu gained less (P < 0.05; 0.04 kg/d) than heifers consuming 15 (0.19 kg/d) and 60 ppm of Cu (0.22 kg/d), but their ADG did not differ from that by heifers consuming no supplemental Cu (0.14 kg/d; pooled SEM = 0.07). Heifers supplemented with 15 ppm of Cu had greater (P < 0.05) liver Cu concentrations on d 84 than those on the 0-ppm treatment and the high-Cu treatments (60 and 120 ppm). Forage intake was less (P = 0.07) by heifers receiving no supplemental Cu than by heifers on all other treatments (6.6 vs. 5.8 +/- 0.37 kg/d). Apparent forage digestibility was not affected by Cu treatment. These data suggest that high rates of Cu supplementation (Cu sulfate; > 60 ppm of total Cu) resulted in less liver Cu accumulation by beef heifers compared with heifers consuming diets supplemented with moderate dietary Cu concentrations (i.e., 15 ppm). As well, the administration of CuO boluses might depress the digestibility of forage nutrient fractions in steers.

Experimental copper poisoning in the camel (Camelus dromedarius)

Copper sulphate was administered by the oral or intravenous route to five dromedary camels. Two camels (1 and 2) receiving copper sulphate at 200 mg per kg per day by drench died within 8 days and camel 3, receiving 100 mg per kg per day by the same route, was slaughtered on day 172. Intravenous injection of 2 mg per kg per day caused the death of camel 4 on day 95 and camel 5, treated similarly, was slaughtered on day 138. Anorexia, dullness, diarrhoea, dehydration and recumbency in camels 1 and 2 were probably clinical signs of copper toxicity. Camels 3, 4 and 5 lost weight. Jaundice was not a prominent clinical sign. The main lesions in camels 1 and 2 were fatty change and necrosis of the liver cells, dilatation and necrosis of kidney tubules, catarrhal abomasitis, enteritis and congestion of the blood vessels of the heart. In camels 3, 4 and 5 the hepatic lesions were mild, with leucocytic infiltration and gastrointestinal and heart lesions were either mild (camel 3) or absent (camels 4 and 5). Cytoplasmic copper granules in hepatic cells were generalized in distribution but more concentrated in the centrilobular zone. In the kidney these granules were confined to the cells of the proximal convoluted tubules. Copper accumulated in the liver and kidneys of all the camels and zinc accumulated in the liver and kidneys of those receiving copper sulphate intravenously. Macrocytic hypochromic anaemia developed in camels 3, 4 and 5 and haemoconcentration in camels 1 and 2. The concentration of serum copper, zinc and iron increased in animals 1, 2 and 4, and unbound iron binding capacity decreased in four camels. There was a rise in the activity of gamma GT, GOT, LDH and CPK in the serum of all the animals. Serum ALP activity, however, increased in camels 1 and 2 and decreased in camels 3, 4 and 5.

Toxic effects of trace element excess

Excesses of many trace elements can cause direct toxic effects to cattle as well as indirect effects that can cause a secondary deficiency of other trace elements. Clinical signs may vary from poor growth and feed utilization to neurologic disorders. Toxic effects vary with the specific trace element in question, the total amount of that element in the diet, the age and condition of the animal, and the presence or absence of certain other dietary components. A diagnosis of toxic trace element interaction is based upon compatible clinical signs in affected animals as well as supporting chemical analyses.

Influence of increasing the calcium and magnesium content of the drinking water on performance and bone and plasma minerals of broiler chickens

Calcium and magnesium contents of drinking water for broiler chicks were adjusted by additions of calcium and magnesium to provide levels of 0, 25, 50, 75, or 100 ppm Mg and 0, 50, or 100 ppm Ca, arranged in a factorial design. During a 3-week trial, increasing the water magnesium concentration significantly (P less than .05) improved feed efficiency and significantly (P less than .05) increased the incidence of swollen hocks and shortened tibia but had no effect on other measures of performance. Bone ash and bone mineral content were not significantly affected by the calcium treatment. However, increasing magnesium level to 100 ppm significantly (P less than .05) increased bone magnesium and phosphorus levels. Plasma minerals were not affected by these same water treatments.

Chronic copper poisoning in dairy cows

Chronic copper poisoning in a dairy herd fed supplementary copper is recorded. Most cows received 11 g of copper sulphate per day but high milk producers received 22.0 g and within 6 months, 3 of them became ill and died. The signs shown by the 3 cows were anorexia, decreased milk production, frequent recumbency and jaundice. Within 4 days of showing signs, the cows died. The autopsy findings were dehydration, anaemia, jaundice, liver damage and intestinal haemorrhage. Liver copper values varied from 1,250 to 2,410 ppm DM.

Chronic copper toxicity of ruminants

There has been an active interest in the toxicology of copper since the middle of the 19th century and a review by Davenport (1953) covers the early work on the hazard to man and animals of both the acute and chronic forms. Review material specific to chronic copper poisoning in farm livestock has also been published by Broughton & Hardy (1934), Eden (1940), Todd (1962) and Bull (1964).

The first description of true chronic copper poisoning in farm animals would seem to be that of Mallory (1925) who produced the condition experimentally in sheep. Beijers (1932) described similar symptoms in sheep grazing orchards which had been sprayed with a copper fungicide, and 2 years later Broughton & Hardy (1934) published their detailed experimental investigations showing the dangers of excessive copper intakes to sheep. The similarity between the symptoms described in these reports and those of ‘yellows’ or ‘toxaemic jaundice’ in Australia was recognized (Bull, 1964) and the experiments of Albiston, Bull, Dick & Keast (1940) confirmed that this naturally-occurring condition was of similar origin. The importance of chronic copper poisoning as a nutritional hazard was, therefore, fully established.