Mineral balances, including in drinking water, estimated for Merced County dairy herds

Dairy producers must increasingly comply with environmental regula- tions at the federal, state and local levels. A key to many of the regula- tions is the development of manure management plans to protect air, water and soil quality. Information on complete nutrient balances and excretion is necessary to control or minimize the loss of nutrients to the environment. Data from 51 ran- domly selected dairy farms in Merced County, in California's Central Valley, was used to evaluate the impact of minerals in drinking water on nutri- ent balances and to characterize the mineral composition of manure from lactating dairy cows. We found that a lactating dairy cow producing ap- proximately 66 pounds of milk daily might excrete 750 ± 117 grams of minerals daily, while the proportion of these minerals attributed to water ranged from 0.3% to 20%. On some dairies, controlling these minerals could reduce manure production and subsequent land applications.