Understanding the soil-plant-animal interaction for minerals in grazing lactating cows for sustainable dairy production in high-altitude Amazonian tropics smallholders.

Smallholder dairy systems in the high-altitude Amazonian tropics of Colombia are characterized by soil and forage conditions with mineral limitations, particularly for calcium (Ca) and phosphorus (P), and ionic antagonisms for potassium (K), magnesium (Mg), and Ca, which compromise mineral homeostasis in grazing cows and limit productivity and sustainability. Despite the importance of these interactions, the soil-plant-animal (SPA) relationship for minerals has not been systematically evaluated in smallholder high-altitude systems in the region. This study aimed to evaluate the soil-plant relationship for minerals and the soil-plant-animal relationship for Ca, P, and Mg in smallholder dairy herds of the indigenous communities located in the High-Putumayo region, Colombia. A cross-sectional study was conducted in 16 smallholder dairy farms (54 lactating cows). Soil samples were characterized for macro- and micronutrients; forage samples were analyzed for mineral composition; and serum Ca, P, and Mg were quantified. All mineral values were standardized to mmol·kg⁻¹ to allow integration across SPA. Principal component analysis (PCA) was used to assess mineral transfer dynamics between soil, forage, and cow serum. Soils across all orders (Andisol, Entisol, Histosol, Inceptisol) showed structural limitations for K and B and low bioavailable Ca and P. Forages exhibited consistently low Ca and P and excessive K and Mg, generating unfavorable Ca/P ratios and strong K-Mg-Ca antagonisms. Soil-plant correlations were weak and inconsistent for most minerals, except for Ca in Entisols. Serum results indicated normal Ca, elevated Mg, and borderline-low P concentrations in cows. SPA correlations revealed a significant positive continuum for Mg (soil-plant r = 0.52; plant-animal r = 0.56) and a significant negative relationship between soil P and serum P (r=-0.64), consistent with P fixation in volcanic soils. PCA suggests that mineral transfer efficiency was strongly dependent on soil order, with forage being the primary mineral source for cows. Mineral imbalances in these high-altitude systems are explained by poor forage mineral absorption and ionic antagonisms rather than absolute soil mineral concentrations. Nutritional mineral management requires a soil-plant-animal perspective, as soil mineral content alone does not reliably predict forage composition or animal mineral status.