Factors influencing the concentration of minerals and metabolites in the plasma of cattle

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Abstract
Summary: One hundred and seventy-seven female Ayrshire cattle from approximately 6 months to 6 years of age were sampled on one occasion to determine the concentrations in plasma of Cu, P, Ca, Mg, Na, K and glucose. Eighty-nine adults, either lactating or dry, were re-sampled 2 months later to estimate concentrations of ketone bodies and free fatty acids. The data were analysed to estimate the contributions of various factors to variation in the concentrations.The combination of age and stage of pregnancy or lactation significantly affected variation in all the constituents although some of this variation was accounted for by milk yield. The concentrations of Cu, Mg, glucose and ketones were significantly affected by milk yield. The presence of ketone bodies in milk (recorded in relation to the first occasion of bleeding only) was associated with a significant increase in the plasma concentrations of Na and Mg and a significant decrease of K and Ca.The herd comprised pairs of genetically related animals. However, the estimates of heritability had large standard errors and only those for P and Ca were significantly positive.