Regression correlation analysis of relationships between blood constituents at various ages and growth rate of calves from birth to 15 months was conducted on 108 calves in Friesian, Jersey and Shorthorn herds. Various blood samples were taken from each calf at 2 weeks, 2 and 3 months of age and analyzed for glucose, potassium, sodium, inorganic phosphorus, calcium, magnesium, total protein, erythrocyte sodium, potassium and magnesium concentrations as well as hematocrit, hemoglobin, total leucocyte count and differential count. Calves were also weighed at birth, 3 and 15 months of age. There were significant correlations between some blood constituents at two weeks and two months of age and growth rates at three and from three to 15 months of age but the coefficients of determination (R2) were less than 0.21. Total leucocyte count, glucose, calcium and absolute monocyte count at three months of age were the best variables for predicting growth rates from three to 15 months of age (R2=0.32). It is concluded that some blood parameters at three months of age could be useful for predicting growth rates from three to 15 months of age.
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