From Soil to Milk: A Critical Review of Mineral Nutrition, Deficiency, and Supplementation in Ruminants and Dairy Cattle

Abstract

Mineral nutrition determines much of the health, fertility, and productive efficiency of dairy cattle, yet the pathway linking soil mineral status to milk mineral output remains fragmented across agronomic, physiological, and nutritional literatures. This critical narrative review synthesises evidence on macromineral and trace mineral metabolism in ruminants, with particular attention to the transition period, mineral–mineral antagonisms, and the comparative merits of inorganic, organic, and hydroxy supplemental sources. Evidence for dietary cation–anion difference (DCAD) manipulation as a strategy against periparturient hypocalcaemia is strong and consistent across meta-analytic and mechanistic studies, whereas evidence for the superiority of organic over inorganic trace mineral sources remains heterogeneous and frequently confounded by digestibility methodology, species, and physiological state. The copper–molybdenum–sulfur antagonism illustrates how soil and forage geochemistry can precipitate both deficiency and toxicity syndromes within the same population, underscoring the inadequacy of fixed dietary recommendations divorced from regional geochemical context. Selenium and vitamin E interact closely in antioxidant defence during the periparturient period, but causal attribution of health outcomes to either nutrient alone is complicated by their biological interdependence. Phosphorus feeding practices on many commercial farms continue to exceed physiological requirement, with direct consequences for manure phosphorus loading and aquatic eutrophication, despite two decades of evidence that reduced dietary phosphorus does not compromise production. Across mineral categories, the review identifies a recurring methodological weakness: reliance on single-herd, short-duration trials with liver or serum mineral concentrations as proxy endpoints rather than validated production, health, or longevity outcomes. Confidence is highest for calcium–DCAD relationships and phosphorus–environment relationships, and lowest for claims regarding organic trace mineral superiority and optimal cobalt supplementation targets. The review concludes that mineral nutrition in ruminants cannot be reduced to fixed dietary concentrations, and that regionally calibrated, interaction-aware, and geochemically informed approaches are required to reconcile animal health, farm economics, and environmental sustainability.