Mixed mineral deficiencies in a dairy herd with subclinical production disorders

An interventional study was performed for a period of 210 days in a dairy farm in Fars province, southern Iran with a history of both poor production and reproduction. Trace mineral deficiencies were suspected as the underlying causes because trace mineral supplements had been dropped from the rations. Serum concentrations of Co, Cu, Fe, Mn, Zn, and also those of Ca, P, Na, Cl, K, and Mg were measured in all lactating and dry cows. The results were compared with the midpoints of the reference values. With the exception of zinc, all studied minerals were significantly low (P < 0.01). The interventions were directed towards the correction of chronic under nutrition with emphasis on trace minerals. The same cows were sampled twice more at days 90 and 210 after the initial sampling, measuring for the same minerals. All minerals increased significantly during the period of the study (P < 0.01). Body condition score, stage of lactation, pregnancy status, and parity did not affect the results of various steps of sampling (P > 0.05). Diets deficient in one or more trace minerals may induce mixed mineral deficiencies involving both categories of major and trace minerals. Such conditions may cause long standing problems in the performance of the herd without clinical signs of deficiency diseases; such problems may not be possible to correct rapidly. In herds suspected of trace mineral deficiencies, measuring serum minerals may be a helpful screening tool.