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Ctr. for Animal Health and Productivity, School of Veterinary Medicine, Univ. of Pennsylvania, New Bolton Center, Kennett Square, PA 19348
Dep. of Agron., Pennsylvania State Univ., University Park, PA 16802
Ctr. for Animal Health and Productivity, School of Veterinary Medicine, Univ. of Pennsylvania, New Bolton Center, Kennett Square, PA 19348
Dep. of Animal and Avian Sci., Univ. of Maryland, College Park, MD 20742
Ctr. for Animal Health and Productivity, School of Veterinary Medicine, Univ. of Pennsylvania, New Bolton Center, Kennett Square, PA 19348
* Corresponding author (dou{at}cahp.nbc.upenn.edu).
Nutrient flow in dairy farming involves animal and field components that are linked by transfers of crops and manure. Connections of the farm to the surrounding environment are created by inputs and outputs of feed, fertilizer, biological N2 fixation, animals and animal products, and nutrient losses to air and water. Because of these linkages among farm components and connections to the environment, an integrated system-level approach would be useful to evaluate farm performance in terms of production efficiency and environmental protection goals. The purpose of this study was to evaluate dairy farm N flow and management by comparing farm performance data with reference values from the Dairy Nitrogen Planner (DNP), an integrated animal and field spreadsheet planning and evaluation tool. Performance data were from two Pennsylvania dairies: Farm 1,109 lactating Holstein cows (Bos taurus), with forages produced on 92-ha crop land and supplemental feeds purchased as directed by nutritional services; Farm 2, 65 lactating cows, with nearly all feeds produced on the lll-ha crop land and no forage quality analysis or ration formulation assistance. Farm performances on Farm 1 and 2, respectively, were (with the difference relative to the DNP projection): annual N input, 17 450 kg (–5%) and 10 670 kg (–10%); milk-N output, 3880 kg (–8%) and 2790 kg (–0.4%); feed-N intake, 20 200 kg (–2%) and 18 820 kg (+1%); and manure N for application, 8550 kg (–14%) and 10 200 kg (+11%). The differences between farm performance and DNP projections identified overall farm organization and crop management opportunities for improved farm system performance on Farm 1. Animal ration balancing was identified as a priority area for enhancement on Farm 2, with subsequent action to adopt the services of a professional nutritionist increasing milk production by 20% and decreasing manure N by 10%.
Received for publication August 11, 1997.
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