Bovine · Endocrine and metabolic · Production medicine
Periparturient hypocalcemia
Older high-producing dairy cow within 48 hours of calving: weak, recumbent, cool extremities, and bradycardia with rumen stasis. Treat with slow IV calcium borogluconate under cardiac auscultation.
Lactational calcium demand outpaces intestinal absorption and bone mobilization. Stage 1 is hypersensitivity and muscle fasciculation, stage 2 is sternal recumbency with an S-curved neck, stage 3 is lateral recumbency and coma. Cardiac effects are the danger: tachycardia with weak sounds, and calcium given too fast causes fatal arrhythmia. Prevention uses prepartum anionic salts to lower DCAD, controlled dietary calcium, and adequate magnesium, because hypomagnesemia blunts parathyroid hormone response. Downer cows that fail to rise after two calcium treatments need evaluation for hypophosphatemia, hypokalemia, toxic mastitis or metritis, and secondary compressive myopathy.