Hematologic and biochemical reference ranges for captive California condors (Gymnogyps californianus).

To provide proper medical evaluation and care for the endangered California condor (Gymnogyps californianus), veterinarians need accurate hematologic and biochemical reference ranges. A retrospective study of blood samples from captive California condors housed at the San Diego Wild Animal Park assessed the samples by sex and age of condor to determine serum biochemical and hematologic reference ranges, including lead and zinc levels. Condors were grouped by age as follows: group 1 included birds less than 30 days of age; group 2 included birds between 30 days and 6 mo of age; group 3 included birds between 6 mo and 5 yr of age; group 4 included all birds greater than 5 yr of age. Significant differences between sexes included higher chloride, cholesterol, and total plasma protein concentration in males as compared to females (P < 0.05). Significant differences between age groups were identified in glucose, potassium, phosphorus, calcium, albumin, total plasma protein, globulin, cholesterol, bile acid, and zinc concentrations, as well as aspartate aminotransferase, alkaline phosphatase, lactate dehydrogenase, and creatine phosphokinase activities (P < 0.05). Additionally, significant differences between age groups were noted in white blood cell count, hematocrit, heterophils, lymphocytes, and eosinophils (P < 0.05). A steady increase in glucose and a decrease in alkaline phosphatase and lactate dehydrogenase activities, as well as cholesterol, bile acid, calcium, and phosphorus concentrations, were correlated with age (P < 0.05). Following application of statistical analysis, condors less than 6 mo of age were identified as unique compared to older cohorts; therefore, two reference ranges are proposed by calculating a 90% confidence interval. Reference ranges obtained from other published avian data, including those for psittaciformes, ratites, galliformes, anseriformes, and raptors, were similar to condors in this study.     

Assessment of a point-of-care biochemical analyzer and comparison with a commercial laboratory for the measurement of total protein and albumin concentrations in psittacines

OBJECTIVE: To determine agreement for total protein (TP) and albumin concentrations measured by a point-of-care biochemical analyzer in heparinized whole blood and plasma samples obtained from psittacines and compare results with those from a commercial laboratory. SAMPLE POPULATION: Hematologic samples from 92 healthy birds. PROCEDURES: Duplicate samples of heparinized whole blood and plasma were obtained. A point-of-care biochemical analyzer was used to determine TP and albumin concentrations. To assess precision, intraclass correlation coefficient (r(i)) and Bland-Altman measures of agreement were used. These results were compared by use of Bland-Altman plots with those obtained from a commercial laboratory that used a biuret method for TP concentration and electrophoresis for albumin concentration. RESULTS: For the analyzer, there was excellent agreement (r(i) = 0.91) between heparinized whole blood and plasma samples for TP and albumin concentrations. Relative error was 0.9% for TP and 0.7% for albumin. Analyzer results correlated well with commercial laboratory results, with a downward bias of 0.6 for TP and 0.3 for albumin. CONCLUSIONS AND CLINICAL RELEVANCE: The analyzer had excellent precision for analysis of heparinized whole blood or plasma samples for TP or albumin concentrations; analyzer values had good agreement with those from a commercial laboratory. The analyzer could be a valid method to measure plasma TP concentrations and provide point-of-care testing in apparently healthy parrots. Biochemical analyzer results for plasma albumin concentration were not validated by results from a commercial laboratory, so conclusions cannot be drawn regarding use of the analyzer in measurement of albumin concentrations in psittacines.     

Assessment of copper and zinc status of farm horses and training thoroughbreds in south-east Queensland

The copper and zinc concentrations in the blood of stabled thoroughbred horses and in Australian Stock Horses mares at pasture, either late pregnant or lactating were determined by an atomic absorption spectroscopic method. The plasma concentration of the trace elements in these apparently normal horses were generally below the "normal" range. The plasma copper, caeruloplasmin copper, whole blood copper and plasma zinc concentrations in the stabled thoroughbreds were 0.76 +/- 0.19 micrograms/ml (n = 82), 0.56 +/- 0.14 micrograms/ml (n = 83), 0.75 +/- 0.18 micrograms/ml (n = 82) and 0.47 +/- 0.09 micrograms/ml (n = 83) respectively. The plasma copper and zinc concentrations of all the brood mares at pasture (pregnant and lactating) were 0.56 +/- 0.20 micrograms/ml and 0.47 +/- 0.11 micrograms/ml (n = 30). The plasma copper concentration of the pregnant group of mares (0.64 +/- 0.18 micrograms/ml; (n = 14) was greater than that of the lactating mares (0.49 +/- 0.21; (n = 16). Variation in the plasma copper concentration was also identified between stabled and farm horses, between horses of different stables and between horses of different ages. The proportion of plasma copper bound to caeruloplasmin was 73 +/- 11.8%. These low concentrations of copper and zinc in the plasma of apparently normal horses are of clinical significance since recent evidence has indicated that copper deficiency appears to promote the development of skeletal abnormalities in foals. An alternative to the use of a single plasma sample to identify the copper or zinc deficient horse was discussed.     

Psittacine plasma concentrations of elements: daily fluctuations and clinical implications.

During the past 2 decades, the potential for excessive exposure of pet birds to zinc has become a concern for many pet bird owners. Ideally, avian zinc toxicosis is diagnosed on the basis of history of exposure to zinc, radiographic evidence of ingested metal, occurrence of melena, detection of an elevated plasma zinc concentration, and response to treatment. However, most pet birds suspected of having zinc toxicosis present with vague signs and lack of radiographic evidence; therefore, the diagnosis relies on the presence of an elevated plasma zinc concentration. A question was, is there a significant diurnal variation in the zinc concentration in psittacine birds and could this be clinically relevant? Because studies in other species have shown that zinc is not the only element that shows a diurnal variation, the authors examined 13 other plasma elements including arsenic, cadmium, calcium, cobalt, copper, iodine, iron, magnesium, manganese, molybdenum, potassium, selenium, and total phosphorus. Fifteen adult psittacine birds housed in the same aviary were used in this study. Three blood samples, separated by 4 hours, were taken from the right jugular vein in each bird. All elements were measured in plasma. Zinc, copper, and molybdenum revealed diurnal fluctuations. The results of this study suggest that interpretation of clinical samples may be more complicated than previously believed. Furthermore, on the basis of the results of this study, it is possible that some avian reference ranges may need to be reexamined.     

The relationship between certain blood cations in cows with milk fever and both the state of consciousness and the position of cows when attended

In one study, a comparison was made of the concentrations and ratios of certain blood cations in 2 groups of cows with milk fever, one showing normal consciousness (n = 8) and the other depressed consciousness (n = 24). There were no significant differences in the mean concentrations of serum total calcium, plasma inorganic phosphorus and potassium, erythrocyte sodium and potassium, the serum calcium/serum magnesium ratio or the plasma sodium/erythrocyte sodium ratio. There were significant differences (all P less than 0.05) in the mean (+/- SD) concentrations of serum magnesium and plasma sodium concentrations, and the plasma sodium/serum magnesium ratio of 0.8 +/- 0.28 vs 1.2 +/- 0.37 mmol/l, 155 +/- 3.0 vs 147 +/- 6.4 mmol/l and 180 +/- 40.1 vs 116 +/- 34.1 for normal vs depressed cows, respectively. In a second study, a comparison was made of the concentrations and ratios of the same blood cations in 3 groups of cows in different positions when attended for milk fever, namely standing (n = 6), sternal recumbency (n = 24) and lateral recumbency (n = 31). There were no significant differences between the mean concentrations or ratios of any of the cations.     

Comparison of biochemical values in serum and plasma, fresh and frozen plasma, and hemolyzed samples from orange-winged Amazon parrots (Amazona amazonica)

BACKGROUND: To the authors' knowledge, on the basis of sample type, storage condition, or hemolysis, differences in serum and plasma biochemical values have not been evaluated in orange-winged Amazon parrots (Amazona amazonica). OBJECTIVES: The purpose of this study was to compare values for biochemical analytes in serum vs plasma, fresh vs frozen plasma, and nonhemolyzed vs hemolyzed samples in orange-winged Amazon parrots. We also compared differences in serum and plasma yield from whole-blood aliquots. METHODS: Fifteen biochemical analytes were evaluated in paired serum and plasma, fresh and frozen plasma, nonhemolyzed and hemolyzed serum and plasma samples from orange-winged Amazon parrots (n = 10) using a wet reagent analyzer. Hemolysis was assessed qualitatively (visually) and quantitatively (hemoglobin [Hgb] measured spectrophotometrically). Serum and plasma yields from 500-microl whole-blood aliquots were determined from centrifuged samples. RESULTS: Analyte values significantly differed among sample groups, but were still within published reference intervals, with the exception of increases in potassium concentration in markedly hemolyzed serum and plasma samples. Clinically important changes in hemolyzed serum and plasma samples included increases in potassium, phosphorus, and albumin concentrations and lactate dehydrogenase activity. The degree of hemolysis assigned qualitatively did not correlate with quantitative Hgb concentration. A significantly greater yield of plasma (288 +/- 13 microL) than serum (241 +/- 44 microL) was obtained. CONCLUSIONS: Significant differences may occur in different sample types, however, only changes in potassium, phosphorus, albumin, and lactate dehydrogenase values in hemolyzed samples were considered clinically relevant. Lack of agreement between qualitative and quantitative Hgb concentration indicates the unreliability of visual estimation. Based on higher sample yield, and lack of clinically relevant differences from serum, plasma is a better sample choice for clinical chemistry analysis in birds.     

Sevoflurane anesthesia in psittacines.

Duration of anesthesia onset (time to intubation) and recovery (time to extubation, sternal and standing) and quality of recovery were compared for sevoflurane and isoflurane in 10 adult psittacines. Both agents were initially administered at an equal volume percentage (2%) rather than at equal minimum alveolar concentrations (MACs), therefore the initial concentration was above the isoflurane MAC for dogs and birds (1.3%) but below the sevoflurane MAC for dogs (2.3%). The time to intubation was significantly longer with sevoflurane because of initially delivering the sevoflurane below suspected MAC for birds. Although recovery times (time to extubation, sternal, and standing) were not significantly different, birds recovering from sevoflurane were less ataxic. Sevoflurane is a suitable inhalant agent for use in these psittacines and merits further study.     

Measurement of superoxide dismutase, diamine oxidase and caeruloplasmin oxidase in the blood of thoroughbreds

Methods were developed for the measurement of superoxide dismutase (SOD), diamine oxidase (DAO) and caeruloplasmin oxidase in the blood of thoroughbred horses. These enzymes were measured in 178 normal thoroughbreds stabled throughout the United Kingdom. The relationships between the activities of SOD, DAO and caeruloplasmin oxidase and the blood concentrations of their associated trace metals (copper, zinc and manganese) were studied in 52 of the thoroughbreds. Trace metals were measured by electrothermal atomic absorption spectrophotometry. No relationships were found between the activities of erythrocyte SOD and serum/whole blood copper, zinc and manganese, or serum DAO and serum copper or zinc concentrations. Caeruloplasmin oxidase in equine blood was found to be correlated to serum copper concentration, r = 0.695 (P less than 0.001) over the normal range. Samples from thoroughbreds with trace metal deficiency or toxicity were not available for study. The observed normal ranges for the activity of these enzymes are as follows: SOD: 50 to 200 units per ml whole blood between 5 and 95 percentiles; DAO: 0.1 to 28.5 units per litre (means = 14.8, SD 7.1) and caeruloplasmin oxidase; 11.6 to 35.8 units per ml (means = 23.7, SD 6.0). For numerical simplicity, the activity of DAO is given in units per litre, compared to units per ml for caeruloplasmin oxidase and SOD.     

Evaluation of plasma (1-->3) beta-D-glucan concentrations in birds naturally and experimentally infected with aspergillus fumigatus

Avian aspergillosis, most often caused by Aspergillus fumigatus, is a common and devastating disease affecting a range of bird species. Early diagnosis is difficult and often unreliable. The current study evaluated the utility of measuring (1-->3)-beta-D-glucan (BG) concentrations in avian plasma samples to aid in the diagnosis of aspergillosis. We evaluated a commercially available BG assay (Fungitell, Beacon Diagnostics) using 178 plasma samples from naturally infected, experimentally infected, and aspergillosis-free birds. Although there was variation in BG concentration, as reflected by high standard deviations, seabirds with confirmed aspergillosis had the highest mean BG concentrations (M = 3098.7 pg/dl, SD = 5022.6, n = 22) followed by companion avian species and raptors with confirmed aspergillosis (M = 1033.8 pg/dl, SD = 1531.6, n = 19) and experimentally infected Japanese quail (Coturnix japonica; M = 1066.5 pg/dl, SD = 1348.2, n = 17). Variation in severity of disease, differences among species of birds with and without disease, and also different levels in environmental exposure likely contribute to the differences among avian groups. The overall sensitivity and specificity of the BG test for diagnosis of aspergillosis in birds was 60.0 and 92.7%, respectively, with an overall optimized avian cut-offvalue of > or = 461 pg/dl for positive disease. Our findings suggest that, although BG concentrations are highly variable between and within different avian groups, it could serve as a useful adjunctive diagnostic test for aspergillosis that is applicable to multiple avian species in some settings, particularly as a negative predictor of infection.     

长白公猪血清和精浆中元素含量对精液品质的影响

本试验旨在研究不同精液品质特征长白公猪血清和精浆中元素含量的差异,分析血清和精浆中元素含量对精液品质的影响。基于107头长白公猪的1402次精液品质记录,将公猪群按照精液可利用率划分为3组:低利用率组(利用率<60%,n=21)、中等利用率组(60%≤利用率≤80%,n=27)和高利用率组(利用率>80%,n=59)。采集每头长白公猪的血清和精浆样品,采用电感耦合等离子体质谱法检测血清和精浆中营养元素和毒性元素含量。结果表明:1)低利用率组长白公猪的有效精子数和精子活力显著低于中等利用率和高利用率组(P<0.01),精子畸形率显著高于中等利用率和高利用率组(P<0.01)。2)不同利用率组间长白公猪的血清和精浆元素含量无显著差异(P>0.05);但在血清和精浆元素含量与精液品质参数相关性分析中发现,精浆铅元素含量与精子活力呈显著负相关(P<0.05),与精子畸形率呈显著正相关(P<0.05)。3)对精浆铅含量分组进一步分析发现,精浆铅含量为0μg/L时长白公猪的精子畸形率显著低于精浆铅含量>10.0μg/L时(P<0.05),精子畸形率降低约6.11%。总的来说,长白公猪精浆中毒性元素铅的存在会通过损害精子活力和形态,影响公猪精液品质。     

Serum Erythropoietin Concentrations Measured by Radioimmunoassay in Normal, Polycythemic, and Anemic Dogs and Cats

Serum erythropoietin (Epo) concentrations were measured by radioimmunoassay (RIA) in normal, polycythemic, and anemic dogs and cats. The serum Epo concentration in normal dogs ( n = 25) ranged from 7 to 37 mU/mL (median, 20 mU/mL); and in normal cats ( n = 11) ranged from 9 to 38 mU/mL (median, 18 mU/mL). Polycythemic animals (PCV < 55% in dogs, > 45% in cats) were classified as those with primary (polycythemia vera), secondary, or polycythemia of uncertain etiology. Dogs with polycythemia vera (PV, n = 8) had a median serum Epo concentration in the normal range (17 mU/mL); cats with PV ( n = 7) also had a median serum Epo concentration that was within the normal range (10 mU/mL). In the category of secondary polycythemias, dogs ( n = 7) (median, 30.7 mU/mL) and cats ( n = 2) had normal Epo concentrations. The median serum Epoconcentration was significantly decreased ( P > .05) in dogs with PV compared with dogs with secondary polycythemias. The median serum Epo concentrations in dogs ( n = 13) and cats ( n = 5) with anemias not due to chronic renal disease were significantly increased ( P > .05) compared with normal dogs and cats. In cats with anemias due to chronic renal disease ( n = 5) the median serum Epo concentration was not significantly different from normal cats. The measurement of the serum EPO concentration may be useful in assessment of anemia or polycythemia but the overlap of values with the normal range in all groups evaluated limit its diagnostic use.     

Increased serum leptin and insulin concentrations in canine hypothyroidism

Serum concentrations of leptin and insulin were compared between gender-matched hypothyroid (n=25) and healthy (n=25) client-owned dogs within comparable age and body condition score (BCS) ranges. Fasted blood samples were collected from each dog and analysed for glucose, cholesterol, triglyceride, leptin and insulin concentrations. Leptin and insulin concentrations were significantly higher in the hypothyroid compared to normal dogs (P=0.006 and P=0.001, respectively) following adjustment for potential confounders. A nearly significant (P=0.051) interaction with BCS was found in the association between hypothyroidism and leptin. Leptin concentrations were significantly higher in hypothyroid dogs compared to normal dogs, in separate analyses for BCS 6 (P=0.036) and 7 (P=0.049). There was no significant difference in glucose concentration between the hypothyroid and normal groups (P=0.84) following adjustment for BCS. This study showed that canine hypothyroidism is associated with increased serum leptin and insulin concentrations, neither of which may be attributed to obesity alone.     

Effect of specimen collection and storage on blood glucose and lactate concentrations in healthy,hyperthyroid and diabetic cats

Abstract: The objective of this study was to compare and investigate differences in glucose and lactate concentrations in sodium fluoride/potassium oxalate (NaF/Ox) plasma and serum in healthy cats and cats with metabolic disease. Glucose and lactate concentrations were determined in routinely processed serum and NaF/Ox plasma obtained from healthy (n = 30), hyperthyroid (n = 27) and diabetic (n = 30) cats, and in samples from 6 healthy cats stored at 25°C or 4°C for 0,1, 2, 4, or 8 hours. The packed cell volume (PCV) of blood collected in NaF/Ox was compared with that of blood collected in EDTA. Mean glucose concentration was significantly (P < .05) lower in NaF/Ox plasma than in serum in all groups of cats, by 0.7–2.5 mmol/L (11–45 mg/dL); the difference was greater in cats with hyperglycemia. Mean lactate concentration was significantly higher in serum than in NaF/Ox plasma in all groups of cats, by 0.4–1.2 mmol/L (3.6–10.8 mg/dL); the difference was greater in hyperthyroid and diabetic cats. In vitro, only serum stored on the clot for ≥ 1hour at 25°C had significantly lower glucose and higher lactate concentrations. The PCV of NaF/Ox-anticoagulated blood was lower than that of EDTA-anticoagulated blood, by 7.0%± 1.4% (P<.01). In conclusion, collection of feline blood in NaF/Ox was necessary to prevent in vitro increases in lactate concentration; however, NaF/Ox artifactually decreased plasma glucose concentration because of RBC shrinkage. The PCV should not be determined on blood collected in NaF/Ox.     

Effect of dietary omega-3 fatty acids on red blood cell lipid composition and plasma metabolites in the cockatiel, Nymphicus hollandicus

Although dietary n-3 fatty acids have been extensively studied in poultry, they have not yet been prospectively investigated in psittacines, despite potential benefits for preventing and treating atherosclerosis, osteoarthritis, and other chronic disease processes. The objectives of this study were to investigate the incorporation of dietary n-3 fatty acids into red blood cells (RBC) and to determine the effects of supplementation of psittacine diets with fish or flax oil on plasma lipids and lipoproteins in the cockatiel. Adult cockatiels were fed a custom-formulated diet containing either 4% (wt/wt, as-fed) beef tallow (CON), 3% fish oil + 1% tallow (FSH), or 3.5% flax oil + 0.5% tallow (FLX; n = 20 per diet group). Baseline measurements were obtained for RBC fatty acid composition, triacylglycerides (TAG), and cholesterol. After 8 to 13 wk on the study diets, plasma chemistry profiles, lipoprotein density profiles, and RBC fatty acid composition were determined. At 8 wk, total plasma cholesterol was least in FSH birds (P < 0.05) and TAG concentrations were less in FSH birds than FLX birds (P < 0.05). Total n-3 fatty acids, docosahexaenoic acid, docosapentaenoic acid, and eicosapentaenoic acid were markedly greater in the RBC of FSH birds than FLX or CON birds (P < 0.05). Alpha linolenic acid was greatest in FLX (P < 0.05). Initial and final BW, and nonlipid plasma chemistry values did not differ among diet groups. No adverse effects of dietary supplementation of cockatiels with 3.5% flax oil or 3% fish oil were observed during the 13-wk feeding period. Although fish and flax oils provided similar total n-3 PUFA to the diets, fish oil caused greater reductions in cholesterol and TAG, and greater total RBC n-3 incorporation. Thus, dietary modification of psittacine diets with long chain n-3 PUFA from fish oil appears safe and may be beneficial to these long-lived companion birds.     

Serum zinc, chromium, and iron concentrations in dogs with lymphoma and osteosarcoma

We compared serum concentrations of zinc, chromium, and iron in dogs with cancer to those of normal dogs. Dogs with lymphoma (n = 50) and osteosarcoma (n = 52) were evaluated. Dogs with lymphoma had significantly lower (P = .0028) mean serum zinc concentrations (mean +/- SD; 1.0 +/- 0.3 mg/L) when compared to normal dogs (1.2 +/- 0.4 mg/L). Dogs with osteosarcoma also had lower mean serum zinc concentrations (1.1 +/- 0.4 mg/L), but this difference was not significant (P = .075). Serum chromium concentrations were significantly lower in dogs with lymphoma (2.6 +/- 2.6 microg/L, P = .0007) and osteosarcoma (2.4 +/- 3.1 microg/L, P = .0001) compared to normal dogs (4.7 +/- 2.8 microg/L). Serum iron concentrations and total iron-binding capacity were significantly lower in dogs with lymphoma (110.8 +/- 56.7 microg/dL, P < .0001, and 236.6 +/- 45.6 microg/dL, P < .0001, respectively) and osteosarcoma (99.6 +/- 49.3 microg/dL, P < .0001, and 245.0 +/- 43.8 microg/dL, P = .0011, respectively) when compared to normal dogs (175.1 +/- 56.7 microg/dL and 277.1 +/- 47.4 microg/dL). Mean ferritin concentration was significantly higher in dogs with lymphoma (1291.7 +/- 63.0 microg/L) than in normal dogs (805.8 +/- 291.1 microg/L, P < .0001) and dogs with osteosarcoma (826.5 +/- 309.2 microg/L, P < .0001). Further investigation is needed to explore the clinical significance of these mineral abnormalities in dogs with cancer.     

Relationship of Peripheral Estrogens and Testosterone Concentrations to Sexual Behavior in Normal and Cystic Cows

Peripheral estrogens and testosterone values on each day of the estrous cycle in the plasma of normal cows (n=6) were compared to those in single serum samples from cystic animals. The highest plasma testosterone was detected on the day before estrus (day 20), and estrogen peaks were observed on days 16 and 20. Serum from cows (n=125) with cystic ovarian degeneration, previously classified as either anestrous or nymphomaniac, was assayed only for either estrogens or testosterone. Additional serum samples were collected from 39 cystic cows to measure both steroids. Almost all of the results from cystic animals were within or below the ranges recorded in the normal cows. No significant differences for either steroid was found between the anestrous or nymphomaniac groups (P>.05). Therefore, it was not possible to demonstrate any relationship between either hormone or behavioral pattern.     

Validation of a novel high-sensitivity radioimmunoassay procedure for measurement of total thyroxine concentration in psittacine birds and snakes.

OBJECTIVE: To validate a novel high-sensitivity radioimmunoassay (RIA) procedure developed to accurately measure the relatively low serum total thyroxine (T4) concentrations of birds and reptiles and to establish initial reference ranges forT4 concentration in selected species of psittacine birds and snakes. ANIMALS: 56 healthy nonmolting adult psittacine birds representing 6 species and 42 captive snakes representing 4 species. PROCEDURE: A solid-phase RIA designed to measure free T4 concentrations in dialysates of human serum samples was used without dialysis to evaluate total T4 concentration in treated samples obtained from birds and reptiles. Serum T4 binding components were removed to allow assay of undialyzed samples. Assay validation was assessed by determining recovery of expected amounts of T4 in treated samples that were serially diluted or to which T4 was added. Intra- and interassay coefficient of variation (CV) was determined. RESULTS: Mean recovery of T4 added at 4 concentrations ranged from 84.9 to 115.0% and 95.8 to 119.4% in snakes and birds, respectively. Intra- and interassay CV was 3.8 and 11.3%, respectively. Serum total T4 concentrations for 5 species of birds ranged from 2.02 to 768 nmol/L but ranged from 3.17 to 142 nmol/L for blue-fronted Amazon parrots; concentrations ranged from 0.21 to 6.06 nmol/L for the 4 species of snakes. CONCLUSIONS AND CLINICAL RELEVANCE: This new RIA method provides a commercially available, accurate, and sensitive method for measurement of the relatively low serum T4 concentrations of birds and snakes. Initial ranges for the species evaluated were established.     

Influence of age, sex, and production class on liver zinc concentration in calves.

Determination of zinc concentrations in the liver of calves and young stock is commonly requested by practitioners and nutritionists to assess whether they receive an appropriate amount of zinc in their diet. However, interpretation of liver zinc concentrations is currently based on information reported for adult cattle for which the health status was unknown and irrespective of production class, sex, and age. A retrospective study of necropsy reports was undertaken to assess the relationships between liver zinc concentrations and age, sex, and production class for calves that did not have a history compatible with zinc toxicosis or zinc deficiency. Results of a generalized least squares, polynomial regression analysis of 474 records found that zinc concentration was not affected by sex (P = 0.29) or production class (P = 0.50). Zinc concentration was significantly associated with linear (P < 0.00001) and nonlinear (quadratic, P = 0.0039) functions of age (r2 = 0.1503), where the concentration decreased from 93 mg/kg wet weight at 30 days of age to 57 mg/kg wet weight at 9 months of age, after which it began to increase. The age-specific 95% confidence limits of the mean concentration for a group of calves and the 95% prediction limits of a single concentration value for an individual animal estimated in this study suggest reconsideration of the recommended limits for liver zinc concentration in calves. As a consequence of the significant influence of age on liver zinc concentration of calves presumably not experiencing zinc toxicosis or deficiency, diagnosis of zinc imbalances based on liver zinc concentration needs to consider age as a diagnostic covariate.     

Zinc and copper plasma levels in Icelandic horses with Culicoides hypersensitivity

Zinc concentration has been shown to have a potent immunomodulatory capacity, particularly influencing T helper cell organisation and cytokine secretion. Culicoides hypersensitivity (CHS) in horses resembles the early and late phase of type I hypersensitive reactions in man, characterised by a shift from T helper cell subtype 1 to T helper cell subtype 2 cytokine profile. In this pilot study, zinc and copper levels were measured in the plasma of 48 CHS-affected and 56 healthy Icelandic horses age 4-25 years (mean approximately 11 years) kept on 7 farms. Affected horses were divided into 3 groups according to the severity of disease. Time of blood collection and feeding management was constant. No differences in zinc or copper plasma levels and plasma copper/zinc ratio were determined among CHS horses and controls by univariate analysis of variance. Therefore, the most significant influences on zinc and copper plasma levels were affected by the location of housing. However, Spearman correlation showed a negative coefficient between the plasma zinc concentration and the severity of CHS (r = -0.31). Due to a probability value of P = 0.002 the null hypothesis r = 0 is rejected, although only 9% of the total variation of plasma zinc is presently explained by its relationship to CHS. In contrast, the Spearman correlation coefficient between plasma copper levels and severity of CHS was not significant (r = -0.14; P = 0.16). The minor deviations in plasma zinc concentrations in association with the severity of CHS may be real or due to neurohumoral or cytokine-mediated mechanisms, but appear too minimal to be relevant.