Blood samples were taken each week from 30 individually-reared heifer calves between 1 and 13 weeks of age and analysed for packed cell volume, blood glucose and Hb; and serum albumin, urea-nitrogen, total protein, inorganic phosphate, Ca, Mg, K, Na, Fe and total iron-binding capacity. All calves were weaned by 6 weeks of age, and were fed ad libitum.
There were significant changes (P < 0·001) in blood concentrations with age for most constituents. Concentrations of albumin and Fe increased and of K decreased steadily over the whole of the period. Glucose and total iron-binding capacity concentrations decreased until about the 6th week of life and then increased.
There were significant correlations (P < 0·05) for both the calves' weight gain and their feed intake from 6 to 13 weeks with the mean concentrations of glucose, inorganic phosphate, Na, albumin and total iron-binding capacity over the same period. Weight gain during this period was also correlated with serum Fe concentration. When weight gains were adjusted for the feed intake, the correlations between weight gain and the concentrations of all blood constituents became insignificant.
There was a significant correlation (P < 0·05) between weight gain after 6 weeks of age and Hb concentration before 6 weeks. However, when weight gain was adjusted for birth weight, this correlation became insignificant.