The Blood Composition of Cows in Commercial Dairy Herds and its Relationships with Season and Lactation

Abstract

SUMMARY Blood samples were taken from groups of lactating and non-lactating cows in 24 dairy herds, which were sampled eight herds at a time, at six-weekly intervals during two consecutive years. The blood samples were analysed for packed cell volume, blood glucose and haemoglobin, and for serum concentrations of albumin, total protein, urea nitrogen, inorganic phosphate, Ca, Mg, K, Na, Cu, Fe and total iron binding capacity. Packed cell volumes and concentrations of urea nitrogen were highest during the summer months of both years. Concentrations of haemoglobin and Fe were significantly higher in the summer of the first but not the second year. Total iron binding capacity was higher in the summer of the second year, the one year in which it was measured. Changes with season in the concentrations of the other constituents were smaller and sometimes inconsistent between the two years. Packed cell volumes and haemoglobin concentrations were consistently higher and concentrations of Mg and Cu lower in the non-lactating cows than in the lactating cows. In summer and autumn Fe concentrations and total iron binding capacities in lactating cows were lower than in non-lactating cows. Inorganic phosphate and Ca concentrations in lactating cows were lower than in non-lactating cows in summer and autumn respectively. For several constituents there were, regardless of season, differences among herds; these were most statistically significant for Cu, albumin and K. The influences of season, lactation and herd are considered in relation to their possible incorporation in the definition of normal ranges of blood composition for use in metabolic profile testing, and the conclusion drawn is that one standard range is adequate for the interpretation of metabolic profile results throughout the year and, with the exception of Hb and PCV, for both lactating and non-lactating cows.