Plasma Total Calcium, Inorganic Phosphate and Magnesium in Cows around Calving in Morogoro, Tanzania

Abstract

This investigation was conducted in 115 cows of second and above parity to provide baseline information on plasma levels for total calcium, inorganic phosphate and magnesium around parturition in the tropical environment. Breeds studied were Tanzania Shorthorn Zebu (TSZ), crosses of TSZ with exotic dairy breeds, and Ayrshire cattle. All animals were kept under traditional pastoral management system. Prepartal blood samples were randomly collected within the last week prior to expected calving and the postpartal blood samples were collected from the same herds within 24 hours after calving. About 51% of the indigenous TSZ and their crosses with dairy breeds had less than 2.00 mmol/1 prepartal plasma calcium concentrations compared to 14.3% of Ayrshires which had 2.48 ± 0.51 mmol/1. Postpartal plasma calcium concentration was less than 2.00 mmol/1 in about 65% of TSZ and their crosses, as opposed to 50% of in Ayrshires. In TSZ and their crosses plasma calcium did not drop postpartum. This drop in Ayrshires was probably due to colostral draw of calcium linked to the relatively high milk production reported in dairy cows (14 liters/cow per day), as compared to 0.5-3 and 4-6 liters/cow/day for TSZ or their crosses, respectively. Mean prepartal plasma inorganic phosphate concentration in all breeds was relatively low compared to normal, varying from 1.11 ± 0.33 to 1.44 ± 0.34 mmol/ I, between farms. An insignificant change was observed postpartum in TSZ and their crosses whereas an unexplained increase postpartum was observed in the Ayrshires. Mean prepartal plasma magnesium was significantly (P<0.01) higher than normal in all breeds, with farm variation ranging from 1.15 ± 0.33 to 1.35 ± 0.56 mmol/1, and with an insignificant change postpartum. This study supports the view that zebu cows and their crosses, are at minimum risk of developing milk fever. In contrast, Ayrshire breed kept in the same area might experience a drop in total plasma calcium at calving and could be prone to periparturient hypocalcaemia like cows of dairy breeds elsewhere.