Factors affecting the hypocalca emic response to protamine. Acta vet. scand. 1975, 16, 51-62. -The hypocalcaemic response to protamine, as a measure of bone resorption rate, was studied in cattle and sheep. Three groups of calves were studied (1-3 days, 2-3 weeks and 4 months old) . The oldest calves showed the greatest response, indicating a more rapid skeletal turnover in these animals, probably related to a higher growing rate. A group of cows was tested at 2 occasions, near parturition and

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... -3 weeks after parturition. The decrease in plasma calcium was small near parturition, while a profound drop was obtained 2-3 weeks post partum, which supports earlier findings that bone resorption is more or less blocked in parturient cows. Young pregnant ewes showed the same degree of hypocalcaemia as adult pregnant ewes but the recovery was more rapid in the young animals. Young rams were given protamine before and after diethylstilboestrol treatment. No differences in calcium response were obtained. Varying plasma phosphate responses were obtained. A pronounced hyperpfiosphataemia was found in the adult pregnant ewes. Diethylstilboestrol caused hypermagnesaemia in the rams. protamine; hypocalcaemia; bone resorption; cat tl e; she e p.