Seasonal and Spatial Variation in Selected Mineral Concentrations of Dairy Cows in the Rift Valley of Ethiopia: A Case Study of Bishoftu and Wonji Shewa

Mineral nutrition is a key determinant of dairy cow productivity and health in Ethiopia’s Rift Valley, where seasonal fluctuations and location-specific feeding systems influence mineral availability. Despite its importance, evidence on seasonal and spatial variations in the mineral status of lactating dairy cows in Ethiopia’s major dairy-producing areas remains limited. This knowledge gap constrains the development of effective, location-specific mineral supplementation strategies. This study assessed seasonal and spatial variations in calcium, phosphorus, magnesium, copper, iron, zinc, and cobalt in lactating dairy cows and their feeds in the dairy production areas of Bishoftu and Wonji. A total of 80 blood and 78 feed samples collected during the dry and wet seasons were analyzed using standard laboratory procedures. Significant location × season interactions were observed for Ca and Fe (p < 0.05). Calcium was marginally adequate, phosphorus remained close to deficiency thresholds, and magnesium and zinc were generally adequate, particularly during the dry season. Copper concentrations were below critical levels and were likely worsened by elevated iron concentrations. Mineral deficiencies were more prevalent in Wonji Shewa (72.5%) than Bishoftu (60%) and were associated with season and physiological status. Lactating cows sampled during the dry season showed the highest deficiency rates. In addition, farmers had limited awareness of mineral deficiency symptoms, especially subclinical reproductive effects. Overall, mineral status varied significantly across locations and seasons, with copper deficiency emerging as the major nutritional constraint. Region- and season-specific mineral supplementation programs, along with farmer education on mineral nutrition and deficiency recognition, should be implemented to improve dairy productivity and cow health.