Changes in some blood constituents associated with parturition in Hereford heifers fed solely on restricted amounts of sorghum grain

Abstract

Fifteen Hereford heifers fed solely on restricted quantities of sorghum grain were bled at intervals during the 24-hr period before and after parturition. Blood samples were analysed for glucose, inorganic phosphate, haemoglobin and packed cell volume. Calcium, magnesium, total protein, albumin and globulin were determined on serum.
There was a moderate decrease in blood glucose levels prior to parturition and a significant rise to peak values at or about parturition. Blood inorganic phosphate levels showed a significant decline. No significant changes were evident in blood haemoglobin, packed cell volume, serum calcium and magnesium levels. Total protein and globulin levels in serum decreased significantly when compared with the values obtained some weeks before and after parturition.
The diurnal variations in blood glucose, haemoglobin and packed cell volume were determined on three steers bled at 2-hr intervals throughout a 24-hr period. Two of these steers were fed solely on restricted amounts of sorghum grain; the other received a restricted amount of lucerne chaff. No regular pattern of diurnal variation was evident, although blood glucose levels tended to rise after feeding. The magnitude of changes due to the time of day at which calving took place was considered insufficient to affect conclusions with regard to changes in blood constituents associated with parturition.