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Abstract

Objective

To explore diurnal variation in blood ionized calcium, sodium, potassium, and chloride concentrations and pH in pregnant dairy cows.

Animals

14 dairy cows in their third or later pregnancy approximately 6 weeks before expected parturition.

Procedure

Throughout a 24-hour period, blood samples were taken at 2-hour intervals and analyzed for ionized calcium (iCa2+), potassium (K+), sodium (Na+), and chloride (Cl) concentrations and pH. Paired t-tests were used to compare initial and final values. Circadian changes were tested by use of repeated-measures ANOVA. Additionally, a nonparametric analysis was performed for each animal to determine minimal and maximal values for the variables.

Results

Significant differences were not detected between initial and final values of any variable. Repeated-measures ANOVA indicated significant diurnal fluctuations in all variables. With the exception of Cl concentration, nonparametric analysis of individual values also revealed significant changes over time.

Conclusions and Clinical Relevance

The magnitude of daily fluctuations does not make it necessary to standardize time of sample collection for routine diagnostic examination of blood iCa2+, Na+, K+, and Cl concentrations and pH. However, it may be important to standardize time of sample collection in comparative studies in which more discrete differences may be identified. (Am J Vet Res 1999;60:945-948)

Free access
in American Journal of Veterinary Research

Summary

Stability of ionized calcium (Ca2+) concentrations and pH values in equine venous samples (n = 12 in each group) stored at 4 C for 3, 9, 24, and 48 hours (blood, plasma, and serum) or for 240 hours (plasma and serum), and at −20 C for 240 hours (plasma and serum), was studied. Storage of equine blood, plasma, and serum samples at 4 C for up to 48 hours and of serum samples at 4 C for up to 240 hours, despite appreciable pH changes, was associated with < 1.5% change in blood, plasma, and serum Ca2+ concentrations. Therefore, Ca2+ concentration in equine blood, plasma, and serum samples stored up to 48 hours and in serum samples stored up to 240 hours at 4 C is of diagnostic use.

Free access
in Journal of the American Veterinary Medical Association

SUMMARY

The stability of ionized calcium (CaI) concentration and pH in sera (n = 14) stored at 23 or 4 C for 6, 9, 12, 24, 48, or 72 hours, or −10 C for 1, 3, 7, 14, or 30 days was evaluated. Also studied were the effects of oxygen exposure, cold handling, and feeding on CaI and pH values. Results indicated that serum CaI concentration was stable throughout 72 hours of storage at 23 or 4 C, and for 7 days at −10 C. Serum CaI concentration significantly (P < 0.05) decreased by 14 days of storage at −10 C. Serum pH was stable for 6 hours at 23 or 4 C, and for 24 hours at −10 C, but significantly (P < 0.05) increased by 9 hours of storage at 23 or 4 C and by 3 days at −10 C. Exposure of the surface of the serum to air immediately before measurement had no effect on CaI or pH values, but mixing serum with air resulted in significantly (P < 0.05) decreased CaI concentration and increased pH. Handling of blood on ice resulted in significantly (P < 0.05) higher serum pH, compared with blood handled at 23 C, but serum CaI concentration was unaffected. Serum obtained at 2 hours after feeding did not have any significant changes in CaI total calcium, or pH values. It appears that if canine serum is obtained, handled, and stored anaerobically, CaI concentration can be accurately measured after 72 hours at 23 or 4 C, or after 7 days at −10 C.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate changes in plasma ionized calcium (Ca2+) and parathyroid hormone (PTH) concentrations in horses competing in endurance rides.

Design—Longitudinal clinical study.

Animals—28 horses.

Procedure—Venous blood samples were obtained from horses before and after racing 80 km. Plasma pH and concentrations of Ca2+, PTH, inorganic phosphorus, albumin, lactate, and magnesium were measured.

Results—Overall, a significant decrease in mean (± SD) plasma Ca2+ concentration (from 6.44 ± 0.42 to 5.64 ± 0.42 mg/dl) and a significant increase in plasma PTH concentration (from 49.9 ± 30.1 to 148.1 ± 183.0 pg/ml) were found after exercise. Exercise also resulted in significant increases in plasma inorganic phosphorus, albumin, and lactate concentrations. No changes in plasma magnesium concentration or pH were detected after exercise. Plasma PTH concentration was not increased after exercise in 8 horses; in these horses, plasma PTH concentration decreased from 58.2 ± 26.3 to 27.4 ± 22.4 pg/ml, although plasma Ca2+ concentration was also decreased.

Conclusions and Clinical Relevance—Plasma Ca2+ concentration was decreased after racing for 80 km, compared with values obtained before racing. In most horses, an increase in plasma PTH concentration that was commensurate with the decrease in plasma Ca2+ was detected; however, some horses had decreased plasma PTH concentrations. (J Am Vet Med Assoc 2001;219:488–490)

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective

To determine effects of exercise on blood ionized calcium (Ca2+) and plasma parathyroid hormone (PTH) concentrations in horses and to compare the effects of exercise-induced and EDTA-induced hypocalcemia on PTH secretion.

Animals

17 horses entered in a show jumping competition and 5 horses given EDTA.

Procedure

Blood Ca2+ and plasma PTH concentrations were measured before and after exercise in the 17 horses entered in the jumping competition. In the other 5 horses, concentrations were measured during infusion of EDTA IV.

Results

Exercise resulted in a significant decrease in blood Ca2+ concentration and a significant increase in plasma PTH concentration, and blood Ca2+ concentration was correlated with plasma PTH concentration. Administration of EDTA resulted in hypocalcemia and an increase in PTH concentration. For the same decrease in Ca2+ concentration, magnitude of the exercise-induced increase in PTH concentration was similar to magnitude of the EDTA-induced increase.

Conclusions and Clinical Relevance

Results suggest that the increase in plasma PTH concentration in horses after exercise is secondary to hypocalcemia and that the increase in PTH concentration seems to be commensurate with the decrease in Ca2+ concentration. (Am J Vet Res 1998;59:1605-1607)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To evaluate coagulation variables in 2 groups of dogs after tromethamine administration.

Animals

13 Beagles.

Procedures

Both groups of dogs received a 30-minute IV infusion of 10 ml of 0.3M tromethamine/kg of body weight. In unsedated dogs (group 1, n = 8), prothrombin time, activated partial thromboplastin time, normalized ionized calcium concentration, platelet numbers, and platelet function were measured prior to treatment, at the end of the infusion, and 1 hour after the infusion. In xylazine-sedated dogs (group 2, n = 5), buccal mucosal bleeding time and plasma percentage of von Willebrand factor antigen were measured before and 1 hour after infusion, and fibrin degradation products concentration was measured 1 hour after infusion. Platelet function was assessed by determining platelet aggregation and by measuring ATP release from the aggregating platelets over 6 minutes, using a whole blood aggregometer, with 20, 10, and 5 μM ADP and 5 and 10 μg of collagen/ml as platelet activation agonists.

Results

There was no significant change in any of the variables measured in either group of dogs, compared with baseline values.

Conclusions and Clinical Relevance

When administered to healthy dogs, tromethamine does not change the coagulation indices measured. (Am J Vet Res 1997;58:777–780)

Free access
in American Journal of Veterinary Research

SUMMARY

Blood ionized calcium (Ca2+) and pH; plasma lactate concentrations; and total protein, total calcium (CaT), albumin, and phosphorus concentrations in serum were determined in 40 healthy horses before (T1), at the finish line (T2), and 10 minutes after the finish (T3) of the cross-country phase of a 3-day-event competition. Mean (± sem) Ca2+ concentrations decreased from 6.22 ± 0.04 mg/dl at T1 to 5.04 ± 0.07 mg/dl at T2 (P ≤ 0.05). This decrease was accompanied by a nonsignificant increase in CaT between T1 and T2. The mean (± sem) percent ionization of calcium decreased significantly (P ≤ 0.05), from 50.9 ± 2.75% at T1 to 40.3 ± 3.58% at T2. Significant increases in mean albumin, total protein, phosphorus, and lactate concentrations and a significant decrease in mean pH were observed at T2 (P ≤ 0.05). At T3, mean Ca2+ and percent ionization had increased, but remained significantly less than resting values. Mean CaT was significantly decreased at T3, compared with values at T1 and T2. Correlation of mean Ca2+ concentration with all other measured variables at each time was evaluated; correlation coefficients between mean Ca2+ and all other variables were low (r 2 ≤ 0.38), indicating low biological significance.

Free access
in American Journal of Veterinary Research

Summary

Mean phosphorus (P) content in bovine rib bone was 102.9, 108.3, and 182.7 mg/g of bone on fresh, dry, and ash weight bases, respectively. Values for calcium (Ca) were 194.3, 203.7, and 344.6 mg/g, respectively, and for magnesium (Mg) were 5.3, 5.5, and 9.4 mg/g, respectively. Mean percentage of ash in rib bone was 59.12%. Expected concentrations of Ca, P, and Mg were determined on fresh, dry, and ash weight bases and for 3 age groups, 3 breeds, and bulls, females, and steers. On an ash weight basis, cattle 6 to 18 months old had 185.74 mg of P/g, 372.52 mg of Ca/g, and 12.37 mg of Mg/g. Those 19 to 36 months old had 182.02 mg of P/g, 322.35 mg of P/g, and 8.09 mg of Mg/g. Those > 36 months old had 174.80 mg of P/g, 340.36 mg of Ca/g, and 6.62 mg of Mg/g. Steers had 183.93 mg of P/g, 352.73 mg of Ca/g, and 10.15 mg of Mg/g. Females had 178.47 mg of P/g, 320.28 mg of Ca/g, and 6.5 mg of Mg/g. Males had 176.15 mg of P/g, all on an ash weight basis. Dairy breeds were found to have 186.08 mg of P/g, 351.25 mg of Ca/g, and 10.47 mg of Mg/g. Cattle of mixed breeding had 177.42 mg of P/g, 341.28 mg of Ca/g, and 6.54 mg of Mg/g. The Africander breed of beef cattle had 167.07 mg of P/g, all on an ash weight basis.

Free access
in American Journal of Veterinary Research

SUMMARY

Hydrated sodium calcium aluminosilicate (hscas), an anticaking agent for mixed feed, was added to the diets of growing wethers (mean body weight, 34.0 kg) and was evaluated for its ability to diminish the clinical signs of aflatoxicosis. The experimental design consisted of 4 treatment groups of 5 wethers each, consuming concentrations of 0 g of hscas and 0 g of aflatoxin (af)/kg of feed (control; group 1); 20 g of hscas/kg (2.0%; group 2), 2.6 mg of af/kg (group 3); or 20 g of hscas (2.0%) plus 2.6 mg of af/kg (group 4). Wethers were maintained in indoor pens, with feed and water available ad libitum for 42 days. Lambs were observed twice daily and weighed weekly, and blood samples were obtained every 2 weeks for hematologic and serum biochemical analyses and for measurement of mitogen-induced lymphocyte-stimulation index. At the termination of the study, wethers were euthanatized and necropsied. Body weight gain was diminished significantly (P < 0.05) by consumption of 2.6 mg of af/kg of feed, whereas body weight of lambs consuming hscas plus af did not differ from that of control wethers. The af-alone treatment increased serum aspartate transaminase and γ-glutamyltransferase activities, prothrombin time, and cholesterol, uric acid, and triglyceride values and decreased albumin, glucose, and urea nitrogen values, and urea-to-creatine ratio. A 27% decrease in lymphocyte stimulation index, increased spleen weight (as a percentage of body weight), and decreased liver weight were induced by af-alone treatment. Results indicate that hscas may be a high-affinity sorbent for af, that 2.6 mg of af/kg of feed induces signs of aflatoxicosis in growing wethers, that lambs may not be as resistant to the effects of af as previously thought, that 2.0% hscas can substantially reduce the toxic effects of 2.6 mg of af/kg, and that sorbent compounds may offer a novel approach to the preventive management of aflatoxicosis in livestock.

Free access
in American Journal of Veterinary Research

SUMMARY

Plasma and milk concentrations of parathyroid hormone-related protein (PTHrP) at various stages of pregnancy and lactation were determined in thirtynine 3- to 16-year-old Brown Swiss and Red Holstein × Simmental dairy cows originating from 4 herds. Eighteen of the cows were separated into 2 groups: low-parity (lp, n = 8) cows if they were in their first or second pregnancy and high-parity (hp, n = 10) cows if they were in their third or greater pregnancy. Blood samples were collected from each cow on 1 occasion, 15 to 5 days before calving, and blood and milk samples were collected daily during 6 days after calving. Serum total and ionized calcium (Catot and Ca2+, respectively) and milk Catot concentrations were also quantified.

A transient postpartum decrease of serum Catot and Ca2+ concentrations was observed, whereas milk Catot concentration was constant. Plasma concentration of PTHrP was detected in 11 of 21 cows by use of an immunoradiometric assay (range, 0.45 to 1.82 pmol/L). Daily mean (± sd) colostrum and milk PTHrP concentrations ranged from 3.25 (± 3.23) to 4.69 (± 1.36) nmol/L in lp cows and 2.74 (± 0.5) to 5.95 (± 0.33) nmol/L in hp cows. In all cows of the hp group and most cows of the lp group, milk PTHrP concentration was highest in the day-1 sample. Milk PTHrP concentration correlated positively with milk Catot concentration in hp cows (r = 0.5959, P < 0.0001). In contrast, there was a negative relation between milk PTHrP and milk Catot concentrations in lp cows (r = −0.3285, P < 0.02). Milk PTHrP concentration was not correlated with serum Ca2+ concentration at postpartum days 5 and 6, when serum Catot and Ca2+ concentrations had returned to prepartum values. Because correlation did not exist between the lowest serum Ca2+ values and milk PTHrP concentration of the corresponding day, milk PTHrP concentration most likely is not a major determinant of Ca transport into milk and the PTHrP released into the blood stream is most likely not a major determinant of the endocrine regulation of serum Catot and Ca2+.

Thus, although it is involved, PTHrP is not a major factor in the integrative endocrine, paracrine, and autocrine regulation of Ca homeostasis in lactating cows. It is hypothesized that Ca may be actively transported from blood into milk with a process modulated by PTHrP. These data suggest that PTHrP produced by the mammary gland is most likely not involved in the pathogenesis of parturient paresis (milk fever) in dairy cows.

Free access
in American Journal of Veterinary Research