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Contact Region 9

Pacific Southwest, Region 9

Serving: Arizona, California, Hawaii, Nevada, Pacific Islands, Tribal Nations

Dairy Manure Management

Technologies for Treating Dairy Manure

Dairy Inputs

Crop Nutrient Management Removal of Nutrients & Salts Anaerobic Digestion/ Thermal Conversion Composting Solid-Liquid Separation
Blue boxes indicate processes. Green boxes indicate products with economic value. *Current practice on
California dairies or pilot project in place. Flow Diagram, PDF (1 pg, 12K) About PDF

Preventing pollution is often more cost-effective than addressing pollution after it enters the environment. In the case of dairies, reducing the amount of nutrients and salts going into the system may reduce the potential for air and water contamination coming out of the system. Nutrients in feed and water in excess of animal requirements add to the nutrient content of the excreted manure, so input management is the first control point to reduce excretion of nutrients from dairy cattle. For example, in one study, when dietary phosphorus for lactating cows fed above the National Research Council-recommended level was reduced by 36%, phosphorus excretion was reduced by the same amount (Reference 1). Another study showed that the nitrogen content of dry matter intake predicts the level of nitrogen excretion (Reference 2). Dietary manipulation can alter the form of nitrogen as well as reduce the amount excreted.

Input management includes the use of dietary additives to enhance cows' milk production. The additives may be yeasts, enzymes, microbials, ionophores, or proprietary materials. Some additives are well researched, and their mode of action is well defined. Some of these are effective as long as the animal is consuming them; others are effective only during the first weeks or months and become less effective over time. For some of the additives there has been research to evaluate effects on manure that is applied to land. Other additives have undergone less rigorous research and little is known of their efficacy in the animal or their subsequent impact on the environment. References

Another way to reduce pollution from dairies is to increase the efficiency of milk production. Replacement animals produce manure and gaseous emissions but no milk. Keeping cows healthy, bred, and lactating for a longer time reduces the number of replacement animals a dairy needs, which reduces the amount of pollution released per unit of milk produced.


  1. Morse, D., H.H. Head, C.J. Wilcox, H.H. VanHorn, C.D. Hissem, and B. Harris, Jr, 1992, "Effects of concentration of dietary phosphorus on amount and route of excretion", J. Dairy Sci. 75:3039-3049.
  2. Tomlinson, A.P., W.J. Powers, H.H. VanHorn, R.A. Nordstedt, and C.J. Wilcox, 1996 , "Dietary protein effects on nitrogen excretion and manure characteristics of lactating cows", Trans. ASAE 39:1441-1448.

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