A study of high lamb liver copper concentrations on some farms in Otago and Southland

Lamb copper status is commonly assessed by measuring copper concentrations in four liver samples collected from lines of lambs sent to meat slaughtering premises. High liver copper concentrations were found in lambs examined in April and May. Five farms with two or more lamb liver copper concentrations greater than 3000 𝛍mol/kg on a wet matter basis and two farms with adequate copper concentrations but less than 3000 𝛍mollkg in the autumn of 1992 were selected for a more detailed investigation into the factors affecting their lamb copper status in 1993. High liver copper status was associated with low pasture molybdenum, grazing paddocks recently topdressed with copper sulphate, supplementing with mineralised drenches and copperised salt licks, and the high copper content in chicory. Lamb liver copper concentrations were significantly (pp<0.05) higher in the autumn than in the summer on two of three farms.     

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.     

Ineffikacy of ivermectin against Cooperia spp. infection in cattle

Ivermectin, either as an injectable or topical formulation, is used widely to control parasites in New Zealand cattle. These formulations have been well documented as having high efficacy against the major nematode species which infect tattle^(1)(2)(3)(4), although the efficacy against adult Cooperia oncophora is reported to be 95%⁽⁵⁾. This is considered to be one of the doselimiting species. There have been two reports of lower than expected efficacy of the topical formulation against Cooperia spp. in cattle. In a slaughter trial, Bisset et al. ⁽⁶⁾ found that ivermectin applied topically at the recommended dose rate of 500 𝛍g/kg failed to achieve a statistically significant reduction in the burden of Cooperia spp. worms compared with untreated calves. The geometric mean of adult Cooperia spp. worms present in the treated calves was 5788 compared with 7524 present in the untreated calves. This reduced efficacy was not attributed to acquired anthelmintic resistance because ivermectin had not been used on the farm previously. In Australia, Eagleson and Allertonc⁽⁷⁾ found in controlled field trials that ivermectin applied topically at 500 𝛍g/kg ranged in efficiency in reducing faecal egg counts from 80.7% to 100% ; four out of 13 trials achieving less than 90% and a further four were in the range of 90–95% reduction. Larvae obtained from the faeces of ivermectin-treated cattle on days 11–14 after treatment were predominantly Cooperia spp.     

Sensitivity and specificity of serum copper determination for detection of copper deficiency in feeder calves

OBJECTIVE: To determine the relationship between serum and liver copper concentrations and evaluate serum copper determination for diagnosis of copper deficiency in juvenile beef calves. DESIGN: Cross-sectional study. ANIMALS: 105 juvenile beef calves. PROCEDURE: Copper concentrations were measured in paired liver and serum samples from 6- to 9-month-old beef calves. Regression models that predicted liver copper concentration as a function of serum copper concentration were developed. Sensitivity and specificity of serum copper concentration for detection of low liver copper concentration were determined, using a range of serum copper concentrations as test endpoints. Positive and negative predictive values were calculated. RESULTS: The association between serum and liver copper concentrations was significant; however, regression models accounted for only a small portion of the variation in liver copper concentrations. For a serum copper concentration endpoint of 0.45 microg/g, sensitivity and specificity for detection of low liver copper concentration were 0.53 and 0.89, respectively. Positive and negative predictive values of serum copper concentration for detection of low liver copper concentration ranged from 0.37 to 0.85 and 0.63 to 0.94, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Regression models are inappropriate for predicting copper status as a function of serum copper concentration. Serum copper concentration is fairly specific for detection of low liver copper concentration but only marginally sensitive when serum copper concentration of 0.45 microg/g is used as a test endpoint. The value of serum copper concentration as a diagnostic indicator depends on prevalence of copper deficiency.     

Copper toxicity in a New Zealand dairy herd

Chronic copper toxicity was diagnosed in a Jersey herd in the Waikato region of New Zealand following an investigation into the deaths of six cattle from a herd of 250 dry cows. Clinical signs and post-mortem examination results were consistent with a hepatopathy, and high concentrations of copper in liver and blood samples of clinically affected animals confirmed copper toxicity. Liver copper concentrations and serum gamma-glutamyl transferase activities were both raised in a group of healthy animals sampled at random from the affected herd, indicating an ongoing risk to the remaining cattle; these animals all had serum copper concentrations within normal limits. Serum samples and liver biopsies were also collected and assayed for copper from animals within two other dairy herds on the same farm; combined results from all three herds showed poor correlation between serum and liver copper concentrations.To reduce liver copper concentrations the affected herd was drenched with 0.5 g ammonium molybdate and 1 g sodium sulphate per cow for five days, and the herd was given no supplementary feed or mineral supplements. Liver biopsies were repeated 44 days after the initial biopsies (approximately 1 month after the end of the drenching program); these showed a significant 37.3% decrease in liver copper concentrations (P <0.02). Also there were no further deaths after the start of the drenching program. Since there was no control group it is impossible to quantify the effect of the drenching program in this case, and dietary changes were also made that would have depleted liver copper stores.Historical analysis of the diet was difficult due to poor record keeping, but multiple sources of copper contributed to a long term copper over supplementation of the herd; the biggest source of copper was a mineral supplement. The farmer perceived this herd to have problems with copper deficiency prior to the diagnosis of copper toxicity, so this case demonstrates the importance of monitoring herd copper status regularly. Also the poor correlation between liver and serum copper concentrations in the three herds sampled demonstrates the importance of using liver copper concentration to assess herd copper status.     

Impact of molybdenum on the copper status of red deer (Cervus elaphus)

AIM: To determine the effect of increasing molybdenum (Mo) intakes on serum and liver copper (Cu) concentrations and growth rates of grazing red deer (Cervus elaphus).

METHODS: Molybdenum- and Cu-amended fertilisers were applied to six 1.1-ha paddocks in a 3 × 2 design. Three levels of Mo were applied on two paddocks at each level in mid April (designated Day 1); levels were: none (control), 0.5 (medium) and 1.0 (high) kg Mo/ha as sodium molybdate. In late May (Day 39), two levels of Cu (none and 3.0 kg Cu/ha, as copper sulphate) were applied to each of the three levels of Mo-treated paddocks. Pasture Mo, Cu and sulphur (S) concentrations were measured at about fortnightly intervals. In late June (Day 74), ten 6-month-old red deer hinds were placed on the six experimental pastures, and serum and liver Cu concentrations were monitored at about monthly intervals for 102 days. The hinds were weighed on four occasions during the trial.

RESULTS: Mean pasture Mo concentrations on Day 56 were 2, 4.6 and 11.3 mg/kg dry matter (DM) for the untreated control, medium and high Mo-treated pastures, respectively. Pasture Cu concentration was 95 mg/kg DM on Day 59, 53 mg/kg DM on Day 90, and 9 mg/kg DM by Day 153. Mean S concentration in pasture was 3.3 (range 3.03–3.45) g/kg DM. Copper application to pasture had no significant effect on serum and liver Cu concentrations in deer so data were pooled within Mo treatment. Mean initial (Day 74) serum Cu concentration was 9.2 µmol/L. In the deer grazing the control Mo pasture, this increased to 10.3 µmol/L on Day 112, before decreasing to 6.4 µmol/L on Day 176. In deer grazing the medium and high Mo-treated pastures, mean serum Cu concentrations were 3.8 and 3.9 µmol/L, respectively, on Day 112, and 2.5 and 3.3 µmol/L, respectively, on Day 176. Mean initial (Day 74) liver Cu concentration was 131 µmol/kg fresh tissue. In the deer grazing the control Mo pasture, this declined to 120 and 52 µmol/kg on Days 112 and Day 176, respectively. In deer grazing the medium and high Motreated pastures, liver Cu concentrations decreased to 55 and 52 µmol/kg fresh tissue, respectively, on Day 112, and 21 and 20 µmol/kg fresh tissue, respectively, on Day 176. Mean serum and liver Cu concentrations were not significantly different between deer grazing the medium and high Mo-treated pastures, and were lower (serum p=0.003, liver p<0.001) in those groups than in deer grazing the untreated control pastures. No clinical signs of Cu deficiency associated with lameness were observed. Deer grazing pastures that had Mo concentrations >10 mg/kg DM had lower (p=0.002) growth rates (100 vs 130 g/day) than those on pastures containing <2.4 mg Mo/kg DM.

CONCLUSION: Increasing pasture Mo concentrations from 2 mg/kg DM to ≥4.6 mg/kg DM significantly reduced serum and liver Cu concentrations in grazing deer. Reduced growth rate was observed at pasture Mo concentrations >10 mg/kg DM.     

The amended insulin to glucose ratio and diagnosis of insulinoma in dogs

Amended insulin to glucose ratios were calculated from the concentrations of serum insulin and blood glucose measured concurrently during either a glucagon tolerance test or after feeding in healthy dogs. Values greater than 30 𝛍U/mg which are supportive of a diagnosis of insulinoma were obtained at certain times during the test period. Amended insulin to glucose ratios calculated from serum insulin and blood glucose concentrations obtained during a glucagon tolerance test and an oral glucose tolerance test on a dog with an insulinoma were less than 30 𝛍U/mg, or equivocal, at different times during the test period. This indicates that under some circumstances healthy dogs may have elevated amended insulin to glucose ratios, and dogs with insulinoma may have a normal amended insulin to glucose ratio. Care is essential for interpretation of amended insulin to glucose ratios, and a diagnosis of insulinoma using the ratio must be made in conjunction with appropriate clinical signs of hvnoglvcaemia.     

Minimal herd sample size for determination of blood copper status of cattle

Copper is required by cattle for synthesis of numerous proteins and enzymes. Copper deficiency in cattle results in a variety of signs ranging from weight loss to diarrhea. In the fall of 1984 and 1985, blood samples were collected from 22 cattle herds near Gunnison, Colo. Approximately one third of the herds were classified as copper deficient (ie, mean serum copper concentration less than 0.6 mg/L). The inherent variability of serum copper concentrations within a herd mandates the determination of the minimal number of cattle to be tested to properly assess the blood copper status of a herd. Coefficients of variation for serum copper concentration were used to calculate a minimal sample size, with a 95% confidence interval for each herd. Minimal sample size ranged from 3 to 55 cattle/herd (ie, 1 to 22% of the herd); this finding suggested that the usual procedure of testing 10% of the herd may be inappropriate.     

Selenium reference ranges in New Zealand cattle

AIM: To compare serum selenium and liver selenium concentrations with whole blood concentrations in samples taken at the same time from unsupplemented cattle, and to use these comparisons to establish a reference range for use in diagnosing selenium deficiency. METHODS: Selenium was measured in concurrent whole blood, serum and liver samples obtained from cattle in unsupplemented herds in the Manawatu, Waikato and Wairarapa regions of New Zealand. The results were statistically analysed. RESULTS: The revised reference ranges are as follows. [table: see text] CONCLUSION: The serum and liver selenium concentrations used as reference values prior to this study were inaccurate for the detection of selenium deficiency.     

Failure of zinc supplementation to prevent severe facial eczema in cattle fed excess copper

CASE HISTORY: A 400-cow dairy unit in the Waikato suffered a severe outbreak of facial eczema (FE) despite consistent zinc supplementation and significantly elevated serum zinc concentrations.

CLINICAL FINDINGS: FE prevention had begun in mid-January 2006, via zinc sulphate supplementation in the water. Photosensitisation was reported on 06 April, contemporaneous with a marked increase in the number of Pithomyces chartarum spores in pasture samples. Within 10 days of this first clinical case, 100 affected cows had been dried off, eight of which subsequently died or were culled. Blood samples were collected from ten affected cows; all had serum zinc concentrations >17 µmol/L, and eight had gamma-glutamyl transferase (GGT) activities >200 U/ml, indicating that the photosensitisation was secondary to liver damage, i.e. probably FE. Further investigation identified that this herd had been receiving excess copper supplementation; 4/6 culled cows had liver copper concentrations within or above the marginal range for copper toxicity.

DIAGNOSIS: Severe FE despite zinc supplementation that increased serum zinc concentrations above recommended levels

CLINICAL RELEVANCE: As zinc supplementation significantly reduces apparent copper status, copper supplementation is often used to counteract this. Previous excess copper intake may reduce the efficacy of zinc in preventing FE, thus copper intake should be assessed prior to the start of zinc supplementation.     

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 µmol/L when serum vitamin B₁₂ concentrations were >375 pmol/L, and not elevated into the range where a liveweight response to supplementation occurred (>10 µmol/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 µmol/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 µmol/L indicate responsiveness to supplementation whilst concentrations <7 µmol/L indicate unresponsiveness. In the range 7–13 µmol/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.     

Copper,Zinc and Molybdenum in Livers of Norwegian Cattle At Slaughter

The concentrations of copper, zinc and molybdenum were measured in samples of cattle liver from 10 slaughter-houses in Norway. A total of 335 samples were analysed. A clear accumulation of copper with age was found, the average copper level in the younger animals (≦ 3 years, n = 194) being 30 µg Cu/g liver wet weight, and in the older ones (> 3 years, n = 141) 59 µg Gu/g. The range in the copper values found was considerable, though significant differences between some of the districts were recorded. Copper concentrations were classified as low (≦10 µg Gu/g) in 9.6 % of the samples. Zinc showed no accumulation with age, nor were there any differences in zinc levels found in animals from different districts, the average level being 32 µg Zn/g liver wet weight. The picture was the same for molybdenum, no differences between age groups or districts being found. The average level was 1.0 µg Mo/g liver. There was no significant correlation between levels of copper, zinc or molybdenum.The supply of copper and zinc to cattle in Norway seems close to sufficient, but copper- and zinc-fortified mineral supplementation of cattle feed is still to be recommended. There seems to be no need for molybdenum supplementation in cattle.     

Tear copper and its association with liver copper concentrations in six adult ewes.

Tear and liver copper concentrations from 6 clinically healthy adult mixed-breed ewes were measured by Atomic Absorption Electrothermal Atomization (graphite furnace) Spectrometry and Flame Absorption Spectrometry, respectively, 7 times over 227 d to determine if their tears contained copper and if so, whether tear copper concentrations could reliably predict liver copper concentrations. To produce changes in liver copper concentration, the diet was supplemented with copper at concentrations that increased from 23 mg to 45 mg Cu/kg feed/day/sheep during the study. This regimen raised liver copper for all sheep to potentially toxic hepatic tissue concentration of greater than 500 mg/kg dry (DM) matter (tissue). The results of the study showed that copper was present in the tears of all sheep. The mean tear copper concentration showed a positive correlation with liver copper concentration (P = 0.003), increasing from 0.07 mg/kg DM at the start to 0.44 mg/kg DM at the end of the study, but could not reliably predict liver copper concentration (R2 = 0.222).     

The effect of oral oxidised copper wire on liver copper in farmed red deer

Twenty-two weaner red deer stags grazed on a marginally copper-deficient property were used to evaluate the effect on liver copper levels of log oxidised copper wire particles given orally. The deer were assigned to two groups on the basis of pre-trial liver copper levels, and grazed together for the duration of the trial from March to October. Liver biopsies were collected from treated and control deer on six occasions at monthly intervals and were analyzed for copper content.

Mean liver copper in the treated group rose from pre-treatment levels of 101.8μmol/kg to a peak of 849.6μmol/kg two months after copper administration. Thereafter, levels fell steadily until six months after administration when they averaged 84.8μmol/kg. The mean liver copper content of untreated deer rose from 102.7μmol/kg at the commencement of the trial, peaked at 255.3μmol/kg after two months, fell to 103μmol/kg one month later and remained low thereafter. The liver copper content in treated deer was significantly higher than for control deer for the duration of the study (p<0.0l for months 1–4 and 6, p <0.05 for month 5).

It is concluded that log oxidised copper wire particles acted to provide adequate liver copper stores for up to five months in deer grazed on a marginally copper-deficient property.     

Bodyweight and serum copper concentrations of farmed red deer stags following oral copper oxide wire administration

A diagnosis of secondary copper deficiency was established on a deer farm with a peat soil type, on the basis of confirmed enzootic ataxia in hinds, liver and serum copper concentrations and pasture and soil element analyses. Seventy-four weaner stags were selected for a trial to investigate a growth response to copper supplementation.

Thirty-seven red and red x wapiti type stags were treated with 4g copper oxide wire particles at four months of age (April). A further 8g copper oxide wire was given in June. Thirty-seven untreated animals acted as controls. Body weights were measured on five occasions, from April 24 to November 26. Serum copper analyses were undertaken on ten deer prior to commencement of the trial, and on seven treated and eight control deer in June, July and October.

Serum copper concentrations ranged from 2.0 to 19.3μmol/l prior to the trial. In June, July and October serum copper ranged from 0.1–6.7, 0.6–5.0, and 1.3–6.3μmol/l respectively, in control deer. In treated deer concentrations ranged from 7.2–14.7, 5.2–10.8, and 6.9–13.7µmoM in June, July and October respectively. The difference between mean copper concentration at each post-treatment sampling date was highly significant, (P<0.001). At the conclusion of the trial (November 26) the treated deer averaged 3.lkg heavier than controls, but this difference was not statistically significant.

In view of these results and the variation in growth response trials in other species, further investigation of the effects of copper on the growth of young deer is warranted.     

Vitamin and mineral supplementation and rate of gain during the first trimester of gestation affect concentrations of amino acids in maternal serum and allantoic fluid of beef heifers

The objective of this study was to evaluate the effects of feeding vitamin and mineral (VTM) supplement and (or) rate of gain (GAIN) during early gestation on amino acid (AA) concentrations in allantoic fluid (ALF) and amniotic fluid (AMF) and maternal serum. Seventy-two crossbred Angus heifers (initial BW = 359.5 ± 7.1 kg) were randomly assigned to one of four treatments in a 2 × 2 factorial arrangement with main effects of VTM supplement (VTM or NoVTM) and rate of gain (GAIN; low gain [LG], 0.28 kg/d, vs. moderate gain [MG], 0.79 kg/d). The VTM treatment (113 g•heifer⁻¹•d⁻¹, provided macro and trace minerals and vitamins A, D, and E to meet 110% of the requirements specified by the NASEM in Nutrient requirements of beef cattle. Washington, DC: The National Academies Press. doi:10.17226/19014, 2016) was initiated 71 to 148 d before artificial insemination (AI). To complete the factorial arrangement of treatments, at breeding heifers were either maintained on the basal diet (LG), or received MG diet which was implemented by adding a protein/energy supplement to the LG diet. Thirty-five gestating heifers with female fetuses were ovariohysterectomized on d 83 of gestation and maternal serum, ALF, and AMF were collected. Samples were analyzed for concentrations of neutral AA: Ala, Asn, Cys, Gln, Gly, Ile, Leu, Met, Phe, Pro, Ser, Thr, Trp, Tyr, and Val; cationic AA: Arg, His, and Lys; and anionic AA: Asp and Glu. In serum, a VTM × GAIN interaction (P = 0.02) was observed for Glu, with greater concentrations for VTM-LG than VTM-MG. Concentrations of serum Cys, Met, and Trp were greater (P ≤ 0.03) for MG than LG. In ALF, concentrations of Glu were affected by a VTM × GAIN interaction, where VTM-MG was greater (P < 0.01) than all other treatments. Further, ALF from VTM had increased (P ≤ 0.05) concentrations of His, Asp, and 12 of the 14 neutral AA; whereas GAIN affected concentrations of Arg, Cys, and Asp, with greater concentrations (P ≤ 0.05) in MG heifers. In AMF, AA concentrations were not affected (P ≥ 0.10) by VTM, GAIN, or their interaction. In conclusion, increased concentrations of AA in maternal serum and ALF of beef heifers were observed at d 83 of gestation in response to VTM supplementation and rate of gain of 0.79 kg/d, which raises important questions regarding the mechanisms responsible for AA uptake and balance between the maternal circulation and fetal fluid compartments.     

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.     

Fractionation of Soluble Copper- and Zinc-Binding Proteins From Cattle Liver

The distribution of copper and zinc among soluble proteins in liver from normal slaughter cattle was examined after gel filtration of the proteins. Gopper- and zinc-binding proteins were mainly separated into three fractions. Varying amounts of zinc were eluted in a fourth fraction of molecular weight less than 2,000. A clear relationship was noted between the amount of copper bound to the low molecular weight fraction (m.w. ~ 10,000) and the total liver zinc concentration. The high molecular weight protein fraction (m.w. > 65,000) dominated in liver with zinc concentrations below 40 µg/g wet weight and total copper concentrations from 16 to 240 µg/g, while in liver with zinc concentrations above 40 µg/g and copper concentrations ranging from 20 to 107 µg/g, the low molecular weight metallothionein-like fraction dominated.     

不同剂量的蛋氨酸铜对肉鸡肝脏病理组织结构和粪便铜含量的影响

选择1日龄健康AA肉仔鸡120只,随机分成4组。使用蛋氨酸铜作为铜源,饲喂玉米-豆粕型基础日粮,对照组饲料铜含量为11mg/kg,3个高铜试验组分别为:110mg/kg、220mg/kg和330mg/kg,试验至60日龄结束。于第12,36,60日龄在各组内随机采血,测定血清丙氨酸氨基转移酶(ALT)、天门冬氨酸氨基转移酶(AST)活性;测量60日龄各组肝脏和粪便的铜含量并观察肝脏组织病理变化。结果显示:①血清ALT和AST活性均在正常范围内,没有异常升高;②110mg/kg和220mg/kg组的肝脏组织中铜含量比对照组有所升高,但是差异不显著(P>0.05),而330mg/kg组则极显著高于其他3个试验组(P<0.01);110mg/kg,220mg/kg和330mg/kg组的粪便中铜含量均极显著高于对照组(P<0.01);③330mg/kg组的肝脏组织大部分细胞中度变性,其他各组病理变化不明显。试验结果表明,日粮中蛋氨酸铜浓度达到330mg/kg时,肝脏内的铜蓄积量会迅速增多且对肝脏造成较大的损伤,粪便中的铜含量随着日粮中铜含量的增加而迅速增多,可能对环境造成不利影响。     

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 × 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 to 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.