The relationship between certain blood constituents in cows with milk fever and the response following treatment with calcium borogluconate solutions

The association between the concentrations of various blood constituents and the responses of cows with milk fever following calcium borogluconate therapy was determined using analysis of variance. In cows which had not received herdsman treatment prior to sampling (n = 63), plasma potassium was the only constituent with a significant effect (p less than 0.01), the mean concentrations for cows classified as unassisted, assisted, or delayed, recoveries, and deaths ranging down from 4.3 to 2.8 mmol/l, respectively. In cows which had received treatment prior to sampling (n = 55) those making unassisted recoveries had significantly lower mean concentrations of serum total calcium than those making assisted recoveries (1.3 v 1.9 mmol/l, respectively, p less than 0.05), and cows making delayed recoveries had significantly lower mean plasma inorganic phosphate concentrations (0.3 mmol/l) than those making unassisted and assisted recoveries (both 0.7 mmol/l, p less than 0.05) and those subsequently dying (1.2 mmol/l, p less than 0.01). Response was not dependent on plasma potassium concentrations in the treated group of cows, and plasma sodium, serum magnesium, and erythrocyte sodium concentrations were not significant in either group of cows.     

Heparinised blood ionised calcium concentrations in horses with colic or diarrhoea compared to normal subjects

Our objectives were to 1) establish ionised calcium (ICa), C-terminal PTH and biologically active PTH (intact molecule) concentrations in blood from normal horses, 2) examine the stability of ionised calcium and acid-base values in stored equine heparinised blood and serum and 3) check the applicability of the formulas based on these parameters in certain disease states. Mean +/- s.d. % ionised calcium in heparinised blood of normal Warmbloods was 51 +/- 2.7 (n = 20) of total calcium, range 1.45-1.75 mmol/l (n = 15) at Michigan State University and 1.43-1.69 mmol/l (n = 20) at Utrecht University. Mean +/- s.d. EDTA plasma concentration for intact +/PTH in normal horses measured 0.6 +/- 0.3 pmol/l (n = 11). Both mean serum and the heparinised blood ionised calcium concentrations changed (not significantly) after 102 h storage at room temperature. Six cycles of freezing and thawing did not affect serum ionised calcium concentration significantly. Ionised calcium concentration and pH in heparinised blood of 20 normal Warmbloods were used to calculate the regression equation for the prediction of the adjusted ionised calcium concentration to a pH of 7.4. The linear regression equation found was: adjusted plasma ICa at pH 7.4 mmol/l = -6.4570 + 0.8739 x (measured pH) + 0.9944 x (measured ICa mmol/l). By means of this formula, mean adjusted ionised calcium concentration in heparinised blood calculated was 100% of the actual value given by the analyser in the normal horses. When using this formula in horses with colic or diarrhoea, mean adjusted ionised calcium concentration was underestimated by 0.2 and 0.3%, respectively. Furthermore, to adjust the measured ionised calcium concentration in heparinised blood to a pH of 7.4 in healthy as well as in 2 groups of diseased horses 2 formulas with a good prediction are now available.     

Changes in canine ionised calcium under three storage conditions

OBJECTIVES: To determine the ionised calcium concentration following aerobic collection of blood and to compare ionised calcium concentration and pH of heparinised whole blood and plasma at 48 hours following collection under three different storage conditions to assess if ionised calcium concentration can be measured retrospectively. METHODS: Blood was collected from 17 dogs for analysis of ionised calcium concentration and pH using a Rapidpoint 400 (Bayer) blood gas analyser. Blood was collected into a commercial preheparinised syringe and into a plain syringe, with subsequent transfer to a commercially available heparinised sample tube. Samples were analysed within 10 minutes, and the remainder was divided for storage. One aliquot was set-aside at room temperature for 48 hours, and the other was immediately centrifuged and the plasma divided for storage at room temperature and at 4 degrees C for 48 hours each. In all samples, ionised calcium concentration and pH were measured again at 48 hours after storage. RESULTS: There was no significant difference in ionised calcium concentration or pH between anaerobically and aerobically collected heparinised whole blood analysed within 10 minutes of collection. At 48 hours, ionised calcium concentrations had decreased under all storage conditions irrespective of the direction of pH change. CLINICAL SIGNIFICANCE: Ionised calcium concentration can be measured in aerobically collected samples within 10 minutes and at 48 hours after collection under the conditions described.     

The effect of intravenous magnesium hypophosphite in calcium borogluconate solution on the serum concentration of inorganic phosphorus in healthy cows

The goal of this study was to determine the effect of intravenous (IV) administration of phosphite on the serum concentration of inorganic phosphorus in cows. Twelve clinically healthy cows were divided into four groups of three. All cows received 600 mL of a 40% calcium borogluconate solution; three cows each received this as a rapid (20 min) IV infusion with and without 6% magnesium hypophosphite, and three other cows each received this as a slow IV infusion (8 h) with and without 6% magnesium hypophosphite. Samples of blood were collected for the determination of serum concentrations of calcium, inorganic phosphorus and magnesium before and 10, 20, 40, 60 and 90 min and 2, 3, 4, 5, 6, 7, 8, 24, 48 and 72 h after the start of treatment. The concentration of calcium increased after treatment in all cows but the increase was most rapid in cows that received the rapid infusion. In cows that received the rapid IV infusion containing magnesium hypophosphite, the mean concentration of inorganic phosphorus decreased significantly 3-4 h after treatment compared with initial serum levels. The serum concentration of inorganic phosphorus did not change significantly in cows that received the rapid IV solution without magnesium hypophosphite or the slow IV infusion with or without magnesium hypophosphite. The serum concentration of magnesium increased after treatment in all cows receiving magnesium hypophosphite but remained unchanged in the others. The rapid infusion of calcium borogluconate without magnesium hypophosphite made all three cows anorexic and hypercalcaemic and the slow infusion made 1/3 anorexic. It is concluded that the IV administration of a calcium solution containing magnesium hypophosphite does not increase the serum concentration of inorganic phosphorus.     

The relationship between reproductive activity and blood calcium in the calcium-deficient hen.

1. The dependence of reproductive activity in the laying hen upon adequate calcium intake has been investigated. 2. The response of plasma luteinising hormone concentration in calcium-deficient, as compared with calcium-replete hens, to injections of luteinising hormone releasing hormone and progesterone suggested that the primary site of reproductive dysfunction is the hypothalamus rather than the pituitary gland. 3. Laying hens, when presented with a calcium-deficient diet, ceased to lay as the plasma ionised calcium concentration decreased to less than 1.0 mM, supporting the view that there is a threshold of blood calcium activity below which reproductive activity ceases. 4. Supplementation of the diet with calcium produced an immediate restoration of plasma ionised calcium concentration to normal, despite an interval of a few days before the plasma total calcium returned to normal and egg laying resumed.     

Treatment of heartwater: potential adverse effects of furosemide administration on certain homeostatic parameters in normal sheep

Diuretics, in particular furosemide, are generally recommended as a supportive treatment in the advanced stages of heartwater in ruminants. However, after what appeared to be possible adverse effects accompanying its use in field cases of heartwater, the effects of this drug on certain blood and urine parameters were investigated in normal sheep at the same dose rates. Diuresis with concomitant natriuresis was significant after furosemide administration, as was the expected plasma volume decrease. Other significant changes included metabolic alkalosis, hypokalaemia and reduced blood ionised calcium. The difference in duration of the diuretic effect and the duration of the changes in blood parameters from c. 3 h and c. 6 h respectively make it difficult to determine a time interval between successive treatments with furosemide. It appears that the probable cause of death of sheep with heartwater is a drastic reduction in blood volume and decreased cardiac output that leads to general circulatory failure. A therapeutic approach that involves further loss of plasma volume due to diuresis appears contradictory. The added effects of potentiating respiratory alkalosis and the terminal drop in blood ionised calcium seen in heartwater-affected animals indicate that the use of furosemide in supportive treatment of this disease is not warranted.     

Plasma concentrations of parathyroid hormone-related protein in dogs with potential disorders of calcium metabolism

The plasma concentrations of total calcium, ionised calcium, albumin, parathyroid hormone and parathyroid hormone-related protein (PTHrp) were measured in 25 dogs with lymphoma, nine dogs with primary hyperparathyroidism and seven dogs with adenocarcinoma of the apocrine gland of the anal sac. Plasma total calcium, ionised calcium, albumin and parathyroid hormone-related protein were measured in 18 clinically normal control dogs. The concentration of PTHrp was high in 12 of the 14 dogs that were hypercalcaemic because of an underlying malignancy but was within the reference range in all the control dogs, in the 17 normocalcaemic dogs with lymphoma and in the seven dogs which were hypercalcaemic because of a parathyroid adenoma.     

Effects of UVB radiation on calcium metabolism in psittacine birds

The effects of providing ultraviolet (uv) radiation (285 to 315 nm, ultraviolet B) on calcium metabolism in two groups of 20 healthy grey parrots (Psittacus e erithacus) fed either a seed or pellet-based diet were investigated. There was a significant increase in the concentration of ionised calcium in the plasma of both groups, independent of the calcium and vitamin D(3) content of the diets fed, and a significant increase in the plasma concentration of 25-hydroxycholecalciferol in only the seed-fed group. In a separate study there were no significant increases in plasma ionised calcium or 25-hydroxycholecalciferol between March and August in a group of 28 South American parrots (Pionus species) exposed to unfiltered natural sunlight.     

Study of calcium homeostasis in feline hyperthyroidism

Thirty cats with untreated hyperthyroidism were blood sampled and their calcium homeosta-tic mechanisms and renal function assessed. The results were compared with those obtained from 38 age-matched control cats. The hyperthyroid group of cats were found to have significantly lower blood ionised calcium and plasma creatinine concentrations and significantly higher plasma phosphate and parathyroid hormone concentrations. Hyperparathyroidism occurred in 77 per cent of hyperthyroid cats, with parathyroid hormone concentrations reaching up to 19 times the upper limit of the normal range. The aetiology, significance and reversibility of hyperparathyroidism in feline hyperthyroidism remains to be established but could have important implications for both bone strength and renal function.     

Diurnal variations in the plasma concentration of parathyroid hormone in dogs

The plasma concentrations of parathyroid hormone (PTH), ionised calcium (Ca(2+)), total calcium, albumin and inorganic phosphorus, and the pH were measured in blood samples obtained from nine dogs during a period of 26 hours. The plasma pth levels fluctuated slightly during the day, by about 20 pg/ml, but there was a distinct peak (42.8 [8.8] pg/ml) at 07.00. Plasma Ca(2+) showed a diurnal pattern in which two peaks (increases of 0.03 mmol/l) were observed at 05.00 and 17.00, and the plasma concentration of inorganic phosphorus showed a similar pattern. There were no diurnal changes in total calcium or albumin.     

Subclinical hypocalcaemia in captive Asian elephants (Elephas maximus)

The hypothesis that hypocalcaemia may play a role in dystocia in captive Asian elephants (Elephas maximus) was investigated. The objectives of the study were to measure the total calcium concentration in elephant plasma; assess the changes in parameters of calcium metabolism during a feeding trial; investigate a possible relationship between calcium metabolism and dystocia; and assess bone mineralisation in captive Asian elephants in vivo. The following parameters were measured: total and ionised calcium, inorganic phosphorous and magnesium, the fractional excretions of these minerals, intact parathyroid hormone, 25-OH-D(3) and 1,25-OH-D(3). Radiographs were taken from tail vertebrae for assessment of bone mineralisation. The mean (sd) heparinised plasma total calcium concentration was 2.7 (0.33) mmol/l (n=43) ranging from 0.84 to 3.08 mmol/l in 11 Asian elephants. There was no significant correlation between plasma total calcium concentration and age. Following feeding of a calcium rich ration to four captive Asian elephant cows, plasma total and ionised calcium peaked at 3.6 (0.24) mmol/l (range 3.4 to 3.9 mmol/l) and 1.25 (0.07) mmol/l (range 1.17 to 1.32 mmol/l), respectively. Plasma ionised calcium concentrations around parturition in four Asian elephant cows ranged from 0.37 to 1.1 mmol/l only. The present study indicates that captive Asian elephants might be hypocalcaemic, and that, in captive Asian elephants, the normal plasma concentration of total calcium should actually be around 3.6 mmol/l and normal plasma concentration of ionised calcium around 1.25 mmol/l. Given the fact that elephants absorb dietary calcium mainly from the intestine, it could be concluded that elephants should be fed calcium-rich diets at all times, and particularly around parturition. In addition, normal values for ionised calcium in captive Asian elephants should be reassessed.     

Feline chronic renal failure: calcium homeostasis in 80 cases diagnosed between 1992 and 1995

Eighty cats with chronic renal failure (CRF) were evaluated in a prospective study to investigate the prevalence and aetiopathogenesis of renal secondary hyperparathyroidism (RHPTH), using routine plasma biochemistry and assays of parathyroid hormone (PTH), blood ionised calcium and 1,25 dihydroxycholecalciferol (1,25[OH]₂D₃). Hyperparathyroidism was a frequent sequela of CRF, affecting 84 per cent of cats with CRF, the severity and prevalence of RHPTH increasing with the degree of renal dysfunction. Compared with an age-matched control population, plasma concentrations of phosphate and PTH were significantly higher and 1,25(OH)₂D₃ concentrations were significantly lower in the two groups of cats presenting with clinical signs of CRF. Significant ionised hypocalcaemia was present only in cats with end-stage renal failure. However, a number of cats were hyperparathyroid in the absence of abnormalities in the parameters of calcium homeostasis measured in this study. There was a significant correlation between plasma phosphate and PTH concentrations.     

Assessment of the cardiotoxicity of tulathromycin in rabbits

The aim of this study was to determine the cardiotoxic potency of tulathromycin. Tulathromycin (10 mg/kg, SC) was administered to ten adult male rabbits, and blood samples were obtained before and after drug administration (0 and 6 hours). Serum cardiac damage markers (troponin I, creatine kinase-MB, myoglobin, lactate dehydrogenase, aspartate aminotransferase), routine serum biochemical values (alkaline phosphatase, alanine aminotransferase, gamma-glutamyltransferase, creatinine, blood urea nitrogen, cholesterol, triglyceride, high-density lipoprotein, amylase, total protein, albumin, glucose, calcium, ionised calcium, sodium, potassium), white blood cell (WBC) and red blood cell (RBC) counts, arterial blood gas parameters (pH, partial carbon dioxide pressure, partial oxygen pressure, actual bicarbonate, standard bicarbonate, total carbon dioxide, base excess in vivo, base excess in vitro, oxygen saturation, packed cell volume, haemoglobin) and serum oxidative status (malondialdehyde, nitric oxide, superoxide dismutase, retinol, β-carotene) were measured. Increased levels of troponin I, creatine kinase-MB and creatinine, and decreased WBC counts, ionised calcium and potassium levels were observed after drug administration. Tulathromycin treatment may cause cardiotoxicity, but its effects may be less dramatic than those of other macrolide antibiotics frequently used in veterinary medicine.     

Treatment of parturient paresis with high-dose calcium

The goal of the present study was to evaluate a calcium dose that was higher than the conventional dose for treatment of parturient paresis in cows. Thirty cows with parturient paresis received 1000 ml of 40 per cent calcium borogluconate solution supplemented with 6 per cent magnesium hypophosphite. Cows in group A received 200 ml of the solution intravenously over a 10-minute period, and the remaining 800 ml via a slow intravenous drip over a six-hour period. Cows in group B received 500 ml of the solution intravenously over a 20-minute period, and the remaining 500 ml via a slow intravenous drip over a six-hour period. Afterwards, the cows were monitored continuously and examined every hour for eight hours. Samples of blood were collected from all the cows before treatment and at 10, 20, 40, 60, 90, 120, 180, 240, 300, 360, 420 and 480 minutes and 24, 48 and 72 hours after treatment. The concentrations of total calcium, ionised calcium, inorganic phosphorus and magnesium were determined. Cows that did not stand within 12 hours of treatment received one or more additional treatments. There was no significant difference in the recovery rate between the two groups. Of the 30 cows, 14 (47 per cent) rised after one treatment and 15 others (50 per cent) were cured after two or more treatments. One cow did not respond to repeated treatments and was euthanased four days after the start of treatment. The results of electrolyte analyses before treatment did not differ significantly between the two groups. In 27 (90 per cent) cows, the concentrations of calcium and inorganic phosphorus were lower than normal and in 3 (10 per cent) cows, only the concentration of inorganic phosphorus was lower than normal.The concentration of total calcium increased markedly ten minutes after the start of treatment in both groups, and at eight hours, the mean concentration of calcium was within the normal range. At 24 and 48 hours, the mean concentration of calcium was below normal, but at 72 hours it was again within the normal range. The concentration of inorganic phosphorus increased slowly in both groups, although it was not within the normal range at eight hours. In both groups, it achieved normal values at 24, 48 and 72 hours.The mean electrolyte concentrations did not differ significantly at any measuring point between cows that stood within eight hours of treatment and those that did not. Our results indicate that increasing the dose of calcium administered does not improve the recovery rate of cows with parturient paresis.     

Effects of xylazine/ketamine on cardiac function and serum ionised calcium in horses

Haemodynamic variables, with emphasis on right ventricular (RV) contractility, were measured in horses prior to, during and following anaesthesia with xylazine/ketamine. In an attempt to elicit mechanisms of anaesthetic-induced alteration of myocardial function, serum ionised and total calcium concentrations were also measured. Xylazine caused decreased cardiac function, including RV contractility, that was not reversed immediately by ketamine but was insignificant from pre-anaesthetic baseline by recovery (45 min following induction). Serum ionised and total calcium concentrations did not change.     

The effect of dietary calcium upon growth rate, food utilisation and plasma constituents in lines of chickens selected for aspects of growth or body composition

1. The effect of increasing dietary calcium from 10.3 to 20 g/kg on 5- to 17-day growth performance and plasma minerals, electrolytes, total protein, albumin and glucose in chickens from 4 lines selected for: high 8-week body weight (W), low abdominal fat (L), high abdominal fat (F) or at random (C) was studied in two experiments. 2. High dietary calcium significantly reduced weight gain and plasma phosphate and potassium but increased food:gain ratio, plasma total calcium, glucose and albumin. 3. Significant correlations were found between plasma total calcium and plasma phosphate (r = -0.5, P less than 0.01), plasma total calcium and protein (r = 0.4, P less than 0.01) and between plasma total protein and albumin (r = 0.55, P less than 0.01). 4. Genotypes differed in their response to dietary calcium content. There was a substantial response in line F but little effect in line L. 5. In contrast to the three other lines, in line F high dietary calcium significantly increased plasma ionised calcium without altering plasma phosphate or total calcium concentration. 6. It was concluded that genetic selection has produced lines which vary in their tolerance to high dietary concentrations of calcium. Birds selected for increased fatness were less tolerant to high dietary calcium than their lean-selected counterparts.     

Long-term effects of dietary anion-cation balance on acid-base status and bone morphology in reproducing ewes

The beneficial effects of anionic salts on calcium metabolism have been shown by supplementing rations with such salts during the last 3 weeks of pre-partum. However, there are few reports on the effects of anionic salts supplementation for periods of 4 weeks or longer on acid-base status, mineral metabolism and bone morphology. This study was conducted to evaluate the effects of the long-term dietary supplementation of anionic salts on the acid-base status, plasma minerals concentrations and bone morphology in sheep. Twenty-seven twin-bearing sheep were assigned to two experimental groups and a control group, depending on dietary cation-anion difference (DCAD) (+272.6, -88.9 and + 164.5 mEq/kg DM, respectively). Sheep assigned to each dietary treatment received their respective rations beginning 6 weeks prepartum and continuing until 12 days post-partum. Diets containing anionic salts induced a mild metabolic hyperchloraemic acidosis from 1 week pre-partum to 2 days post-partum that was completely compensated by non-respiratory mechanisms. These changes on acid-base status were accompanied by an increase of plasma ionized calcium levels. Plasma total calcium, phosphorus and magnesium concentrations were not affected by dietary treatment. Parathyroid hormone concentrations were related to the concentration of ionized calcium of plasma and were higher in sheep fed the cationic diet. Plasma osteocalcin levels were increased in sheep fed the anionic diet and cortical bone remodelling occurred in all the animals during late pregnancy in light and electron microscopy observation, but was particularly evident in the sheep fed the anionic diet. Bone turnover might be stimulated because of the role of the bone in buffering systemic acidosis. The data suggest that anionic salts ameliorated calcium metabolism around parturition by increasing bone resorption and the concentration of ionised calcium in plasma, possibly mediated by a mild hyperchloraemic metabolic acidosis induced by the salts.     

Calcium homeostasis and intact plasma parathyroid hormone during exercise and training in young Standardbred horses

Physical exercise is known to affect calcium homeostasis in horses, but there is little information on the hormonal regulation of calcium metabolism during exercise. In order to evaluate the effects of exercise and training on calcium homeostasis and intact plasma parathyroid hormone, 7 untrained Standardbred horses were studied in a 6 week training programme. These horses were accustomed to running on the treadmill 3 weeks before onset of training and were exercised on a high-speed treadmill with an initial incremental standardised exercise test (SET 1: 6 incremental steps of 5 min duration each; first step 5 m/s, increase 1 m/s). SET 1 was followed by a lactate-guided training programme (6 weeks in total) with 2 types of exercise in alternating order with a day of rest after each work day: high-speed exercise (HSE) of 15 min duration, starting at VLa4, continuous increase in speed every 60 s by 0.3 m/s (14 incremental steps); and low-speed exercise (LSE) at a constant velocity at VLa2.5, duration approximately 60-90 min. The whole training programme consisted of 8 HSE and 8 LSE sessions. HSE and LSE were calculated to require the same energy expenditure. A final SET (SET 2) finished the training programme. Blood samples for lactate, plasma total calcium [Ca], blood ionised calcium [Ca2+], blood pH, plasma inorganic phosphorus [P(i)] and plasma intact parathyroid hormone [PTH] were collected before, during and after SETs 1 and 2, before and after the first and eighth HSE and LSE. During SETs 1 and 2, HSEs 1 and 8 there was a decrease in ionised Ca2+ and pH and a rise in lactate, intact PTH and P(i). LSEs 1 and 8 resulted in an increase in pH, whereas lactate, ionised Ca2+, total Ca, P(i) and intact PTH were not affected. No changes in calcium metabolism were detected during training. Results of this study suggest that intact PTH is a mediator in counter-regulation of exercise-induced hypocalcaemia.     

Effects of dietary acidity on calcium balance and mobilisation, bone morphology and 1,25 dihydroxyvitamin D in prepartal dairy cows

The effect of an acid or alkali diet was investigated in 14 mature dairy cows during the last 28 days of pregnancy. The acid diet reduced the incidence of parturient hypocalcaemia compared with the alkali diet and was associated with higher blood ionised calcium and plasma chloride concentrations and lower blood pH and acid-base excess before parturition. Plasma 1,25-dihydroxyvitamin D concentrations before parturition were increased by the acid diet but the concentrations of parathyroid hormone and intact 1–86 parathyroid-hormone-related peptide were unaffected. The estimated fractional calcium absorption and calcium mobilisation rate during an ethylenediamine tetraacetic acid infusion were increased by the acid diet 14 days before parturition. Cortical bone remodelling occurred in all the animals during late pregnancy but was particularly evident in the cows given the acid diet. The data suggest that an acid diet ameliorates parturient hypocalcaemia by enhancing calcium mobilisation before parturition by increasing calcium absorption and bone resorption, these increases possibly being mediated by increases in the plasma concentration of 1,25-dihydroxyvitamin D.     

The effect of oral calcium lactate in postpartum cows

The oral administration of calcium lactate for prophylaxis of bovine parturient paresis has been promoted for a number of years. The goal of the present study was to investigate the effect of this treatment on the serum concentrations of calcium, inorganic phosphorus and magnesium in parturient cows. Five fresh calved cows were given a drench containing calcium lactate and 5 control cows received the same drench but without calcium lactate. There were no significant differences in the serum concentrations of total and ionised calcium and magnesium between treated and control cows within 24 hours of treatment. Because the calcium lactate drench did not significantly affect calcium concentrations in the blood of fresh cows, it appears highly questionable whether the administration of calcium lactate decreases the risk of bovine parturient paresis. Based on our results, the oral administration of calcium lactate can not be recommended for prophylaxis of bovine parturient paresis.