Differences in the concentrations of certain blood constituents among cows in a dairy herd

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Abstract
SUMMARY: Blood samples were taken on six occasions from a herd of 172 Friesian, Ayrshire and Friesian × Ayrshire dairy cows, and analysed for packed cell volume, blood glucose, haemoglobin and serum albumin, total protein, urea nitrogen, inorganic phosphate, Ca, Mg, K and Na. Differences in blood composition among cows, adjusted for differences in stage of lactation, were demonstrated for all blood constituents (P < 0·001) with the variation among cows proportionally largest for globulin and total protein and smallest for Na. Correlations between blood constituents were for the most part small.Globulin and total protein concentrations increased with age (P < 0·001) and concentrations of inorganic phosphate, albumin, Mg, Na and urea decreased with increasing age (P < 0·001 for inorganic phosphate and Mg, P < 0·01 for albumin, Na and urea). Frequency distributions of the concentrations of the blood constituents adjusted for age and breed showed significant deviations from normality for globulin (P < 0·05) and Hb (P < 0·01).There were significant relationships between the concentrations of globulin and total protein of 43 dams and their daughters (P < 0·01 for globulin, P < 0·05 for total protein). There were also significant differences in groups of daughters of different sires for concentrations of urea, globulin, total protein, albumin, Mg, Ca, K and PCV (P < 0·01 for urea and globulin, P < 0·05 for the other constituents).