Hypocalcaemia

It is also known as milk fever or parturient paresis. The disease occurs due to imbalance in input and output of calcium and is characterized by reduced ionic calcium level in blood and clinical sings of general muscular weakness, paresis, hypothermia and depression.

Etiology: The disease occurs due to deficiency of ionic calcium in blood during the parturition when the demand is increased about 3-fold more. Its deficiency may be caused due to (i) excess loss of calcium in colostrum than its absorption from intestine, (ii) defective absorption of calcium from intestine during parturition, and (iii) insufficient mobilization of calcium from its stores to meet out the demand. Insufficiency of parathyroid gland at parturition affects the calcium mobilization. The calcium and phosphorus ratio in the diet should be appropriate (2.3:1) for proper absorption from the intestinal tract. Excessive use of some antibiotics like neomycin, streptomycin and gentamycin also reduces calcium ionization. So, their use in late pregnancy should be done with care. Disease occurs commonly in high yielding dairy animals, mostly in third or fourth lactation as milk yield is higher in these lactations. It is seen in dairy animals within 72 h or just at the parturition but rarely, it occurs during third to eighth week of parturition.

Pathogenesis: This disease is caused due to (i) excess loss of calcium in colostrum after parturition, if such loss is beyond the capacity of absorption from intestine and mobilization from bone; (ii) impairment of calcium absorption from intestine at parturition; and (iii) the failure in mobilization of calcium from stores to meet the immediate demand. When parathyroid hormone or vitamin D is not present in sufficient amount, disease develops. Diets high in sodium and potassium also result in hypocalcaemia. Due to low calcium, muscular tone, cardiac output, arterial blood pressure and rumen, abomasal and intestinal motility are reduced which in turn cause hypothermia, muscular weakness, constipation and low consciousness.

Clinical signs: This disease occurs in bovines in 3 stages - stage of excitement, sternal recumbency and lateral recumbency. In stage of excitement and tetany, animals are off feed, hypersensitive and reveal muscle tremors, shaking of head, protrusion of tongue, ataxia, stiffness of hind legs, and grinding of teeth. They fall easily and usually have normal body temperature at this stage. In sternal recumbency stage, animal looks drowsy, unable to stand and has dry muzzle, cold extremities, subnormal temperature, low consciousness and the head is turned into flank. Intensity of heart sounds is reduced and pulse is weak. The animal shows the sings of ruminal stasis, constipation, relaxation of anus and dilatation of pupils. In lateral recumbency stage, coma, flacidity of muscles, marked depression, subnormal temperature, impalpable pulse, weak and inaudible heart sound and bloat are noticed. In sheep and goat, similar symptoms with sternal recumbency occur commonly.

Diagnosis: The disease is diagnosed with history of parturition, clinical symptoms and by seeing the absence of calcium in urine by Sulkowitch test. In the blood samples, levels of calcium and phosphorus are decreased while activities of AST and CPK enzymes are increased. High PCV, eosinopenia, neutrophilia and lymphopenia are also noticed.

Hypocalcaemia is differentiated from hypomagnesemia which is associated with excitement, loud heart rate and muscle tremors. Ephemeral fever is characterized by high rise in body temperature, watery nasal discharge, and has seasonal occurrence. Ketosis reveals ketotic smell from urine and milk, muscle tremors, and tetany. Coliform mastitis has excessive leukopenia and involvement of udder. Fat cow syndrome is associated with apathy, scanty soft faeces, ketonuria and involvement of liver. Downer's cows may have slightly elevated body temperature, audible heart rate, alertness and usually normal feeding, urination, defaecation and rumination.

Treatment: T he anima ls respond quickly with calcium therap y. Calcium borogluconate 25% solution is administered @ 400-800 ml in large animals and 40-60 ml in sheep or goat by intravenous route or subcutaneously. In affected animals, it is good to give half of the dose intravenously and remaining by subcutaneous route. The diet should be provided with proper calcium and phosphorus ratio of 2.3:1. Similarly, the sodium and potassium contents should be low while that of sulphur and chloride should be comparatively high as it helps in maintaining anion cation balance and reduces occurrence of disease. The cases which relapse after calcium therapy should be given dextrose, phosphorus and magnesium. A dose of 500 ml dextrose of 40% solution, 200 ml of 15% sodium acid phosphate and 250-350 ml of 15% magnesium sulphate should be used. Administration of vitamin D and its metabolites, or analogs are of value in preventing the disease.