Effect of 1,25 dihydroxyvitamin D3 on the calcium and magnesium metabolism of lactating cows

Administration of 1,25 dihydroxyvitamin D3 (1,25(OH)2D3) to lactating dairy cows resulted in increased dietary calcium absorption and elevated concentrations of plasma calcium. Dietary magnesium absorption was unaffected by 1,25(OH)2D3 however, plasma magnesium concentration was depressed. Injections of 1,25(OH)2D3 were effective in elevating plasma calcium concentrations in both normal and hypomagnesaemic cows. This indicates a potential use for 1,25(OH)2D3 to prevent and treat hypocalcaemic cows with or without concurrent hypomagnesaemia.     

1,25 dihydroxyvitamin D3 increases plasma magnesium and calcium in sheep fed liquid diets low in calcium and magnesium

Sheep given a liquid diet low in calcium and magnesium by infusion directly into the abomasum developed concurrent hypocalcaemia and hypomagnesaemia, with plasma concentrations of calcium and magnesium decreasing to 2.0 and 0.4 mmol/l respectively. Treatment of these hypomagnesaemic sheep with 1,25 dihydroxyvitamin D3 (1,25(OH)2 D3) increased the plasma calcium, magnesium and phosphorus concentrations with plasma calcium increasing to 2.5 mmol/l and plasma magnesium to 0.6 mmol/l. Plasma magnesium increased despite a small but significant increase in the daily excretion of magnesium in the urine, and the amount of magnesium derived from either bone and/or intestine must have been greater than the amount lost in the urine. Since in other experiments we have demonstrated that plasma calcium remains within the normal range when a liquid diet adequate in magnesium but low in calcium is infused, these results imply that either synthesis of and/or end organ response to 1,25(OH2) D3 is impaired in magnesium deficient sheep.     

Postmortem biochemical markers of experimentally induced hypomagnesaemic tetany in cattle

Severe hypomagnesaemia and tetany were induced in 10 lactating cows by feeding them semi-synthetic low magnesium diets and the animals were used to study the stability of postmortem markers of hypomagnesaemic tetany. There were significant relationships between the concentrations of magnesium in either cerebrospinal fluid (CSF) or plasma and either aqueous or vitreous humour. The onset of hypomagnesamic tetany was also associated with low magnesium concentrations in plasma, CSF and aqueous and vitreous humour. Magnesium concentrations less than 0.25 mmol/litre in fresh aqueous humour may be indicative of severe hypomagnesaemia and possible tetany in lactating cows, but the concentration of magnesium in aqueous humour was unstable postmortem. The concentration of magnesium in vitreous humour was relatively stable and a concentration of less than 0.55 mmol/litre could be used as a diagnostic marker of tetany in cattle for up to at least 48 hours postmortem, at ambient temperatures typical of Northern Ireland.     

Hypomagnesaemia in beef cows wintered in Ontario.

A field experiment was undertaken in northern Ontario in order to assess the magnesium status of beef cattle raised in the area. Magnesium status was assessed using several criteria including blood and urine magnesium levels, and bone biopsy samples. Eighteen groups each containing four pregnant Shorthorn beef cows were used. Each of the following three mineral feeds were offered to six groups throughout the experiment: a mineral feed without magnesium, a mineral feed containing 8% magnesium in the form of magnesium oxide and the third containing sequestered magnesium with a magnesium level of about a tenth of that in the mineral feed containing magnesium oxide. During the winter, when the cows were housed indoors, they were fed grass silage. Six groups, two of each mineral feed, remained indoors throughout the summer. The other 12 groups were turned out to pasture on May 25 and continued receiving the appropriate mineral feed. There were no differences in serum magnesium owing to magnesium-supplementation treatments observed at any time during any experiment. Serum magnesium levels fell drastically in all groups before the cows were released to pasture, implying that the hypomagnesaemic condition was attributable to the stress of yarding. The rate of recovery from hypomagnesaemia was slower in the cows released to pasture than in those kept indoors. Urine samples from cows returned to the pasture were indicative of low magnesium status. At the end of the experiment, the magnesium levels in the bones of the housed animals were higher than for those on pasture. In spite of severe cases of hypomagnesaemia, no clinical signs of this metabolic condition were observed.     

Regional brain monoamine concentrations and their alterations in bovine hypomagnesaemic tetany experimentally induced by a magnesium-deficient diet

Monoamines are important brain neurotransmitters. An investigation was carried out to determine if hypomagnesaemic tetany was associated with alterations in regional brain monoamine concentrations in bovines. The results, established in cows with normal magnesium status, demonstrated that regional differences existed in the distribution and concentration of brain monoamines in the adult bovine, which were similar to those in other species. In magnesium-deficient cows, severe hypomagnesaemia and lowered cerebrospinal fluid (CSF) magnesium concentrations were associated with significant alterations in monoamine concentrations in some brain regions. Alterations in 3,4-dihydroxyphenylalanine (DOPA) and dihydroxyphenylacetic acid (DOPAC) concentrations in the corpus striatum, and dopamine (DA) in the cerebral cortex and cerebellum were recorded. These regions play an important role in both voluntary and involuntary motor function, and therefore these alterations may play a role in the aetiology of hypomagnesaemic tetany. However, there was no significant change in DA concentrations in the corpus striatum (the main dopaminergic region in the brain) associated with hypomagnesaemia. In addition, a significantly lower norepinephrine (NE) concentration in the corpus striatum of hypomagnesaemic animals was also recorded. Norephinephrine is generally excitatory and therefore lowered NE concentrations would be expected to result in depression rather than stimulation of motor function.     

Paresis and unusual electrocardiographic signs in a severely hypomagnesaemic, hypocalcaemic lactating bitch

A severely hypocalcaemic, hypomagnesaemic lactating bitch exhibited clinical signs of pulmonary oedema, paresis, dementia, gastrointestinal ileus and urinary bladder atony. The total calcium, ionised calcium and magnesium levels were extremely low. The clinical picture was very different from the one typically encountered in canine lactation tetany, and instead resembled bovine postparturient paresis. Muscle tremors, rigidity and seizures were not part of the acute clinical picture, but rather atony, weakness and paresis. General muscle dysfunction probably resulted from the extremely low ionised calcium levels in combination with very low levels of magnesium and possibly potassium. Heart failure and atony of the urinary bladder and intestines were probably a result of the severe hypocalcaemia. The alteration in calcium to magnesium ratio may have depressed neuromuscular transmission, leading to paresis and atony. The unusual electrocardiogram possibly also resulted from abnormal magnesium and calcium cation levels.     

Calcium, magnesium, phosphorus, chloride and glucose in the blood of cattle following intravenous infusion of solutions with various calcium and magnesium concentration aimed at improving the treatment of hypomagnesemia]

Recent findings on changes in the mineral content of tissues in bovine hypocalcaemia and hypomagnesaemia show the necessity of using different mineral solutions for the treatment and prevention of these conditions. Infusion of 2% CaCl2-6H2O with 10% MgCl2-6H2O and 5% glucose one after the other or in combination produced severe functional changes in cardiac activity and respiration. Recommended concentrations for treatment or prophylaxis of hypomagnesaemia were 10 g magnesium chloride and 2 g calcium chloride, or alternatively 12 g magnesium adipate and 5 g calcium gluconate, in 100 ml of distilled water (total dose 500 ml). This was well tolerated and it overcame the mineral deficiency in tissues.     

Iatrogenic hypocalcaemia during parenteral fluid therapy of diarrhoeic calves

Acid-base balance and electrolyte concentrations, including ionised calcium, were monitored during intravenous fluid therapy of 11 collapsed diarrhoeic suckler calves aged five to 10 days. Six healthy calves of similar age and type were used to provide control data. All the diarrhoeic calves were severely acidotic (TCO2<12 mmol/litre). Isotonic sodium bicarbonate (1-3 per cent) was administered until the metabolic acidosis was half corrected, as indicated by the TCO2 increasing to 17 to 24 mmol/litre when the infusion was changed to an extracellular volume replacement fluid containing 144 mmol/litre Na+, 35 mmol/litre HCO3-, 4 mmol/litre K+ and 113 mmol/litre Cl- which was administered until the calf was discharged. Milk feeding was started as soon as the calf had a suck reflex. The treatment was successful in 10 calves. At admission the diarrhoeic calves were hypocalcaemic compared with the control calves, but their ionised calcium was significantly higher, with significantly less calcium being protein bound. Treatment with isotonic sodium bicarbonate resulted in a significant improvement in acid-base balance, but both total and ionised calcium decreased significantly, the decrease in ionised calcium being proportionately greater owing partly to a significant increase in the protein binding of calcium. The mean total, bound and ionised calcium concentrations were all significantly lower in the treated calves after they had received isotonic sodium bicarbonate than in the control calves. Further treatment with replacement fluid had no significant effect on any of the parameters apart from pCO2 which increased significantly. Milk feeding had no significant effect on plasma calcium concentrations. The calves' mean ionised calcium concentration was significantly lower at the end of the treatment than before it, but there was no difference in the mean total and bound calcium concentrations. The calves' mean plasma potassium and magnesium concentrations decreased significantly during the course of the treatment.     

Magnesium metabolism in the laying fowl

Laying fowls were fed on synthetic diets containing 49, 118, 486, 655, 1242 and 2176 mg/kg magnesium. Magnesium intake and plasma concentration were significantly correlated: 49% of the plasma Mg was diffusible. The hens fed on magnesium‐deficient diets (49 to 118 mg/kg magnesium) were hypomagnesaemic while those receiving 2176 mg/kg were hypermagnesaemic. In the deficient hens the liver showed magnesium depletion, increased calcium content and decreased fresh weight. Skeletal muscle was unaffected by the dietary variations in Mg. The magnesium concentration in the femur was positively correlated with the plasma magnesium concentration. Femurs showed a loss of magnesium and increased mineralisation (especially of the medullary bone) in deficient hens, and a net gain of magnesium in the birds receiving 2176 mg/kg magnesium. The magnesium concentrations in egg shells, albumen and yolk were also positively correlated with the plasma magnesium concentration. The shells of eggs laid by magnesium‐deficient hens were thin, a reflection, apparently, of the reduced plasma calcium levels associated with the decreased bone mobilisation.     

Tetany associated with magnesium deficiency in suckling beef calves

Sudden death losses occurred in 4-month-old beef calves with clinical signs of muscular dysfunction, including tetanic spasms. Gross lesions were not diagnostic. Microscopic lesions consisted of deposition of calcium salts in the elastic fibers of the arteries in the heart, lungs, and spleen and in the trabeculae of the spleen. Focal areas of interstitial nephritis were characterized by infiltration of lymphocytes and plasma cells. Samples of hay and silage that the cattle were consuming were low in magnesium. Calves with spasms responded to magnesium salts given intravenously, and losses ceased after a magnesium-containing supplement was fed free choice to the calves and cows.     

Investigations of D-lactate metabolism and the clinical signs of D-lactataemia in calves

Five clinically healthy calves received an intravenous injection of 25 g sodium D-lactate (223 mmol) in 100 ml sterile water and five control calves were given the same volume of 0.9 per cent sodium chloride. Two clinical examiners who were blinded to the status (test or control) of the calves observed that between eight and 40 minutes after the injections the calves that had received sodium-D-lactate could be distinguished with certainty from the control calves on the basis of their clinical signs, for example, an impaired palpebral reflex, somnolence and a staggering gait. One-compartment and two-compartment analyses of the changes in the plasma concentration of D-lactate, and its renal clearance, indicated that the calves metabolised considerable amounts of D-lactate.     

Magnesium concentrations in the ventricular and lumbar cerebrospinal fluid of hypomagnesaemic cows

Samples of ventricular and lumbar cerebrospinal fluid (CSF) were taken at intervals from six lactating dairy cows, made hypomagnesaemic by feeding a magnesium-deficient diet. Initially the ventricular CSF had a higher magnesium concentration than lumbar CSF but as the cows became hypomagnesaemic the magnesium concentration in ventricular CSF decreased more rapidly than that in lumbar CSF. Tetany occurred when the concentration of magnesium in ventricular CSF fell below about 0.5 mmol litre-1. Intravenous infusion of magnesium into two hypomagnesaemic cows increased the concentration of magnesium in ventricular CSF before there was any change in the lumbar CSF. Newly formed CSF from the ventricles appeared to be more sensitive to changes in the concentration of magnesium in plasma than lumbar CSF which equilibrates with the diffusible magnesium of the central nervous system.     

Hemoconcentration in calves and its relation to the hematologic, protein, mineral and electrolyte profile

The dynamics of hematological, protein, mineral and electrolytic profile was examined clinically in nine calves when the hemoconcentration was induced experimentally. The hemoconcentration occurred after diarrhea caused by the per os application of 12 g saccharose per one kg of live weight. The hemoconcentration culminated six hours after application. The calves where the hemoconcentration did not exceed the critical value were included in the first group, and the calves with the extreme hemoconcentration values in the other group. In the first group (with the increasing hemoconcentration degree), a statistically significant increase was found in the values of hematocrit, erythrocytes, hemoglobin, total protein in blood serum and total immunoglobins and a statistically insignificant increase in the levels of leucocytes, inorganic phosphorus, serum calcium and sodium. Serum potassium and magnesium showed the inverse dynamics, i. e. the decrease. In the second group (with the extreme hemoconcentration), hyperkalemia and slight hypermagnesemia were identified, while the other parameters showed deviations similar to those observed in the first group. After the rehydration of animals by a preparation without any influence on the studied parameters, the hemoconcentration and the parameters under study stabilized, while in the second group the hemoconcentration was increasing even during the rehydration and the levels of serum potassium and magnesium showed different tendencies. As follows from the results, in the calves suffering from scours accompanied by hemoconcentration the correction of the parameters of metabolic profile is necessary.     

Biochemical changes induced by hypomagnesaemia in lactating cows and ewes

Severe hypomagnesaemia was induced in lactating cows and lactating sheep by feeding them magnesium-deficient diets for 17 and 14 days, respectively. Hypomagnesaemia in cows was associated with abnormally high rates of change in the numbers of leucocytes, neutrophils, monocytes and platelets. There were increases in the concentration of iron in the liver of the hypomagnesaemic ewes and in the heart of the hypomagnesaemic cows, which were not associated with a haemolytic process. The percentage of some of the peroxidisable fatty acids was lower in the heart tissue of hypomagnesaemic cows, but the reduction was not associated with significant lipid peroxidation.     

Enteral Fluid Therapy: Biochemical Profile of Horses Treated with Hypotonic Enteral Electrolyte Solutions Associated with Energy Sources

The present study evaluated the biochemical profile of horses that received hypotonic electrolyte solutions associated with energy sources by enteral route in continuous flow using a small caliber tube for naso-esophageal administration. Experimental design was a latin square 3 × 3 with two replicates and three periods. The assays were carried out with “six adult females horses”, divided into three groups submitted to the following treatments each: electrolyte solution containing dextrose (ESDext)—“5 g sodium chloride, 0.5 g potassium chloride”, 1 g of calcium gluconate, 200 mg of magnesium pidolate, and 15 g of dextrose diluted in 1,000 mL of water with measured osmolarity of 264 mOsmol/L; electrolyte solution containing maltodextrine (ESMalt)—5 g of sodium chloride, 0.5 g of potassium chloride, 1 g of calcium gluconate, 200 mg of magnesium pidolate, and 15 g of maltodextrin diluted in 1,000 mL of water with measured osmolarity of 203 mOsmol/L; and electrolyte solution containing sucrose (ESSucr)—“5 g sodium chloride, 0.5 g potassium chloride”, 1 g of calcium gluconate, 200 mg of magnesium pidolate, and 15 g of sugar diluted in 1,000 mL of water with measured osmolarity of 234 mOsmol/L. The electrolyte solutions were administered at the dosage 15 mL/kg/h during 12 hours. Hypotonic enteral electrolyte solutions that contain maltodextrin (ESMalt) and dextrose (ESDext) were effective to increase glycemia in horses without causing any adverse effects, whereas ESSucr presented slight effect on blood glucose, but without causing electrolyte imbalances.     

The effect of induced hypomagnesaemia and hypermagnesaemia on the erythrocyte magnesium concentration in cattle

Hypomagnesaemia was induced in ten yearling Friesian heifers by starving them for forty hours while hypermagnesaemia was induced in seven Friesian calves (about two and half months old) by intramuscular magnesium sulphate (MgSO₄) injection. The plasma magnesium (PMg) concentration decreased (P<0.05) during starvation and increased (P<0.05) following MgSO₄ administration. However the erythrocyte magnesium (EMg) concentration did not show any significant change either with starvation or following the MgSO₄ administration. These results show that sudden and significant changes in PMg concentration do not have any significant effect on EMg concentration. Accordingly EMg concentration may be a better indicator of long-term body Mg status and during hypomagnesaemic tetany could show whether the decrease in PMg concentration was sudden or gradual.     

Dietary magnesium and urolithiasis in growing calves

The effect of high levels of dietary magnesium (1.4%) alone or in combination with elevated calcium (1.8%) or phosphorus (1.6%) on growth and health of male calves was evaluated during a nine week feeding trial after weaning. Twenty calves were randomly divided into 4 feeding groups consisting of controls, high magnesium, high magnesium and calcium or high magnesium and phosphorus. Elevated dietary minerals caused decreased feed intake and growth rate. Blood urea nitrogen and serum creatinine levels were greatly elevated in calves fed high magnesium or magnesium and phosphorus and serum urea nitrogen was moderately elevated in calves fed high magnesium and calcium. These elevations suggested the occurrence of renal damage as a result of microcrystalline obstruction of renal tubules. Serum magnesium levels were three times normal in calves fed high magnesium or magnesium and phosphorus, but only twice normal in calves fed high magnesium and calcium. High dietary magnesium resulted in a significant depression in blood calcium level. This effect was somewhat overcome by additional dietary calcium Three calves fed the high magnesium diet and two calves fed the high magnesium and phosphorus diet developed urinary tract obstruction. The chemical composition of uroliths recovered from these calves was calcium apatite. Elevated dietary magnesium has been shown to be a cause of urolithiasis in growing male calves. Additional dietary calcium, but not phosphorus, appears to protect calves against urolithiasis induced by elevated dietary magnesium.     

Effects of Jatropha curcas on calves.

Jatropha curcas seed was fed to six calves at doses of 2.5, 1 and 0.25 g/kg once and to two other calves at 0.025 g/kg up to 14 days. The onset of toxic manifestations in the six calves was rapid and death occurred within 19 hours of administration. The two calves that received daily the lowest dose of J. curcas showed signs of poisoning and died within 10 to 14 days. The clinical signs of diarrhoea, dyspnoea, dehydration and loss of condition were well correlated with the pathological findings. There was an increase in aspartate aminotransferase, ammonia and potassium and a decrease in total protein and calcium in the serum of jatropha-poisoned calves.     

Clinicopathology of gout in growing layers induced by high calcium and high protein diets

1. An experiment was conducted to test the independent and combined effects of high dietary calcium and protein concentrations on the induction of visceral gout in growing birds of a layer strain. 2. One hundred and sixty healthy birds were randomly divided into 4 groups at 35 d of age. The different groups were given 4 diets containing normal or high concentrations of dietary calcium or crude protein in a 2 x 2 factorial experiment for 30 d. The diets contained normal calcium (Ca) and crude protein (CP) (NCNP, 8.5 g Ca/kg and 175g CP/kg), high calcium and normal protein (HC, 36.3 g Ca/kg and 175 g CP/kg), normal calcium and high protein (HP, 8.8 g Ca/kg and 245 g CP/kg) or high calcium and high protein (HCHP, 36.8 g Ca/kg and 242 g CP/kg), respectively. 3. Typical visceral gout was induced by the HCHP diet. The HCHP and HC diet caused severe kidney damage. The HP diet did not cause kidney damage, but significantly increased plasma uric acid and inorganic phosphorus concentrations. 4. The HC diet significantly increased plasma uric acid, calcium and sodium, but significantly decreased plasma inorganic phosphorus, potassium and magnesium concentrations. The HCHP diet significantly increased plasma uric acid, calcium and sodium. 5. Urine volumes were significantly higher on the HCHP and HC diets than on the control. The growers raised on HC and HCHP diets had significantly higher total quantity of 24 h urinary excretion of uric acid, calcium, magnesium, inorganic phosphorus and potassium and a significantly lower 24 h urinary excretion of sodium. The growers fed on the HP diet had a higher 24 h urinary excretion of uric acid and inorganic phosphorus than the control. 6. It is concluded that growing layer birds should not be fed on layer rations.     

Abdominal distension in collapsed diarrhoeic calves: biochemical findings and treatment.

Thirty-seven of 53 diarrhoeic calves hospitalised for intravenous fluid therapy were classified as very severely acidotic (total carbon dioxide less than 8 mmol/litre) by using a Harleco apparatus. All the calves were given intravenously 10 to 20 litres of electrolyte solution which contained 144 mmol/litre sodium, 4 mmol/litre potassium, 113 mmol/litre chloride and 35 mmol/litre bicarbonate, and in addition the 37 very severely acidotic calves received 400 ml of 1M sodium bicarbonate in the first 5 litres of fluid administered. Sixteen of the 37 very severely acidotic calves had a distended right flank, suggesting the presence of a dilated fluid-filled viscus. Neither their history nor other clinical signs were useful predictors of the distension. The distended calves had significantly higher plasma concentrations of sodium and chloride, and significantly lower plasma creatinine concentrations than the calves which were not distended. Treatment was successful in all the 21 non-distended calves but four of the distended calves died despite treatment. The resolution of the distension in the successfully treated calves, coincided with a significant increase in plasma bicarbonate concentration and the passage of large amounts of malodorous mucoid faeces.