In terms of nutrient balances, modern dairy systems are more complex than ever before. Feed is the primary nutrient input on the average California dairy farm. Whole-farm nutrient balances are an important tool for evaluating the economic and physical viability of each dairy farm, improving nitrogen imbalances and complying with environmental regulations. This article discusses the concept of nutrient balances and variables affecting the improvement of nitrogen imbalances in California dairy systems.

Dairy producers must increasingly comply with environmental regulations at the federal, state and local levels. A key to many of the regulations 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 randomly selected dairy farms in Merced County, in California’s Central Valley, was used to evaluate the impact of minerals in drinking water on nutrient balances and to characterize the mineral composition of manure from lactating dairy cows. We found that a lactating dairy cow producing approximately 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.

Dairy producers seldom test or examine incoming cattle, although these important biosecurity practices are recommended. This pilot project examined risk management decisions that producers make when faced with test-positive animals in purchased groups of dairy cattle, in order to provide information on disease risks and conditions that could affect animal health and performance. New arrivals to seven herds at dairy farms in four California counties were examined and tested for a range of conditions. The most common findings were bovine leukosis virus (33% of cattle purchased) and male reproductive abnormalities (16% of bulls purchased). Once testing results were known, producers made a variety of risk management decisions. Although testing costs for some conditions outweigh the benefits of finding an infected animal, an individual producer’s decision to test new animals most likely depends on their knowledge of the pros and cons as well as their risk tolerance.