Scientific Advances in Animal Nutrition: Promise for the New Century: Proceedings of a Symposium (2001)

DANNY G. FOX

Cornell University

North Americans have become increasingly concerned about water and air quality. In an attempt to address this problem, the U.S. Department of Agriculture (USDA) and the Environmental Protection Agency (EPA) have released a strategy for comprehensive nutrient management planning on farms for protecting water quality. This strategy sets the direction for how nutrients will be managed and how water quality is protected. This program proposes that every livestock farm have a nutrient management plan within the next 10 years. Large farms with over 1,000 animal units are being required to develop plans now. Records that document how nutrients are managed will be required. A monitoring program will also be instituted to verify that federal and state standards are met.

The amount of nitrogen and phosphorus used per unit of milk or meat sold must be decreased. Amount of nitrogen and phosphorus applied per acre will be critical because, if the nutrients are not recycled, they will accumulate and become a potential risk for leakage into ground or surface water. Therefore, viable alternatives for moving excess manure off the farm, and alternatives for processing it for that purpose are being developed and evaluated.

The USDA/EPA proposal focuses on crop and manure nutrient management more than animal feeding. I agree with this approach to address the immediate problem of keeping the manure nutrients from leaking into the surface and ground water. However, we have found there are great opportunities for reducing excess nutrients on the farm while reducing feed costs on the animal

feeding side. In a case study on one farm, instituting a crop nutrient plan that focuses on efficient use of manure nutrients increased profits by $3,000. Use of a computer model, the Cornell Net Carbohydrate and Protein System (CNCPS), to accurately predict animal requirements and feed nutrients available to meet requirements while improving feeding management resulted in an additional annual increase in returns over feed costs of $42,000, while reducing nitrogen and phosphorus excretion by 25 to 33 percent.

Equations and coefficients in CNCPS and similar computer models are derived from the Committee of Animal Nutrition (CAN) reports and supplements, as well as published data. So, current summaries about nutrient requirements are important for modelers to accurately predict independent effects of variables that influence requirements and feed nutrient availability and utilization.

We have conducted studies on a range of dairy and beef cattle feeding farms (the smallest was a 40-cow pasture-based dairy and the largest were a 500-cow dairy and a 1000-head beef feedlot) to determine if there were problems with excess nutrients. Measurements revealed that 59 to 85 percent of the nitrogen from nitrogen fixation and the phosphorus and potassium from feeds was retained on the farm and not exported as milk or meat, regardless of type or size. Volatilization of nitrogen contributed to a 67 to 75 percent loss of excess nitrogen. On one farm, a leaching model, based on soil type characteristics and rainfall, predicted that 10 percent of excess nitrogen enters ground water. This was validated when we measured levels of nitrogen and phosphorus above federal water quality guidelines during the growing season in a stream containing only surface and groundwater from that farm’s cropland.

Our conclusion is yes; we in agriculture have a problem with excess nutrients and we must assume ownership of its potential for impacting water quality. It will be of increasing concern, because everyone desires clean water and air. But producers must recognize that they may have problems with excess nutrients. A survey of 25 dairy farmers in 1995 revealed they believed that farms did not create environmental problems; instead, they believed the problems were created by people who talked about the environment. They also stated that they planned to continue to make decisions based on economics, and not the environment, until regulated to do so. In our state, we are working to create an awareness that there is a problem and to encourage farmers to become proactive to address the problem voluntarily.

To better understand the problem of excess nutrients and their impact on water quality, we conducted a study at Cornell’s Animal Science Teaching and Research Farm. Our data revealed a 50 percent increase in milk production with no increase in cow numbers over the 15-year period studied and with no change in crop acres or yields. As a result, this increase in milk production was

supported by increased importation of feed nutrients on the farm, which increased soil phosphorus from 7 to 30 pounds per acre. One farm that applied the same amount of nutrients to the cropland as the Cornell farm did (170 lb. of nitrogen and 32 lb. of phosphorus per acre), had stream levels of 14.4 ppm of nitrogen and 0.41 ppm of phosphorus, which are above EPA standards. Four wells in corn fields sampled over the 15 years had a 54 percent increase in nitrate content. Some of the wells beginning with nitrogen levels at about half of the EPA standard now exceed it. Nitrogen in wells in the unfarmed hillsides remained low (less than 0.6 ppm, compared to the EPA standard of 10 ppm). Obviously nutrients on most farms are diluted by water from other sources and from hillsides, so they will not reach these levels. However, this study demonstrates that livestock farms do have potential to impact water quality and that producers should be concerned.

We have been conducting studies on dairy and beef farms in the state of New York to develop a process for whole farm nutrient management planning to address the problem of excess nutrients. The first step was to develop computer software for herd, manure, crop, and soil nutrient management planning. We call this family of computer programs the Cornell University Nutrient Management Planning System (CUNMPS). The CUNMPS integrates research and experience about livestock nutrition, crop requirements, and manure management. In four dairy farm case studies, use of the herd nutrition computer program along with improved feeding management indicated nitrogen and phosphorus in manure can be reduced by up to one third, while feed costs can be reduced by $50 to $130 per cow annually. The manure, crops, and soils computer program determines the amount of manure nutrients that can be recycled by the crops, and where and when to apply them to protect water quality. Each of these programs is being used separately by herd feeding advisors and crop advisors.

Several whole farm plans have been developed with the complete CUNMPS on case study farms and are being evaluated as they are implemented. On one 500-cow dairy, intensively managed grass was substituted for corn and alfalfa on wet, erodable hillsides, with corn and alfalfa grown in the flat valley land. The grass provides a sink for excess manure nitrogen, while reducing nutrient runoff and soil erosion. In the new plan, annual cost of milk production is predicted to decrease by $40,000. With changes in herd and crop nutrient planning, the percentage of nitrogen and phosphorus feed nutrients that are purchased are expected to decline 44 and 48 percent, respectively.

On a 350-cow dairy, changing four management practices (grouping and feeding cows by amount of milk production, improving forage quality, and maximizing crop yield to the potential for the soil resource and climate) is

expected to decrease the excess nitrogen and phosphorus on the farm by 44 and 51 percent, respectively, while reducing annual feed costs by over $96,000.

Our studies show that increasing milk income to overcome rising costs by using improved feeding, genetics, and management technologies to increase milk production per cow versus increasing cow numbers is better for both the environment and farm profits. In the 350-cow dairy case study, increasing milk production 10 percent by increasing milk production per cow versus increasing cow numbers was projected by the CNCPS to result in 10 percent less nitrogen and 12 percent less phosphorus, with a $34,000 reduction in annual feed cost.

Improving farm sustainability involves improving economic viability on each farm while protecting the environment. These improvements require feeding recommendations that are based on predicting animal requirements and nutrients available from feeds accurately in each unique production setting. This requires the ability to use farm specific inputs to account for variables such as animal type and level of production, feed composition, and environmental conditions. Farm plans will need to integrate all the components of that particular farm, such as animals, soils, crops, manure management, and farm business records. Complex computer models can be used for this task, given the availability of powerful computers at low cost and increased availability of information on farms such as feed intake and feed analyses, crop yields, soil tests, and information from the satellite-based Global Information System (GIS). In many situations, we now have more information than we are capable of translating into recommendations for feeding and cropping. So, CAN reports will become even more important, as there is increased need for recommendations in the form of equations and coefficients developed from published studies, which can be converted into prediction equations for use in computer models that allow for farm specific feeding recommendations.

Our experience indicates whole farm nutrient managment plans developed must be farm-specific and cost-effective, or they will not be implemented. The animal nutritionists and crop specialists now advising farmers must work more as a team to create an integrated whole-farm nutrient management plan. To provide the science-based tools needed, scientists at academic institutions must work more as a team so that the scientific information can be integrated for application rather than presented to the farmer as a series of independent best management practices. This collaboration poses a challenge to our land grant institutions because our reward system favors individual accomplishment more than team contributions and the development of new science over the integration and application of accumulated knowledge.

The time to address the problem of excess nutrients on farms is now, not sometime in the future. An example is the New York City (NYC) watershed. The city of New York obtains its water supply from one of the largest surface storage and supply systems in the world: 19 reservoirs and 3 controlled lakes in 8 counties north and northwest of NYC. This system provides on average 1.34 billion gallons of high-quality unfiltered water daily to the over 9 million people living in the NYC metropolitan area through a 6000-mile grid of water mains. Recently, the EPA mandated that the city build a water filtration plant that would filter all of this water, which would cost over $6 billion to build, or take steps to protect the water quality in these reservoirs, which store over 550 billion gallons of water. A Watershed Agricultural Council (WAC) was formed to develop a partnership with farms in the NYC watershed area to protect water quality. Partnerships were developed with Cornell Cooperative Extension and University Scientists, Soil and Water Conservation Districts, and the USDA Natural Resources Conservation Service to provide technical support and tools for developing whole farm nutrient management plans. The goal of these plans is to minimize nutrients, pathogens, and sediments leaving the farm in surface and ground water. The NYC Department of Environmental Protection provides funds for developing whole farm plans to meet water quality goals, scientific support for managing on farm pollution sources, and implementation of all structural changes and management of the plan as approved by the WAC. Participation is voluntary. However, because of the commitment of NYC to share the cost, a large number of farms in the NYC Watershed now have nutrient management plans in place. Similar programs have been and are being developed in other watersheds in the state.

Nutrient management planning can be a win-win for agriculture, the environment, and the U.S. population. A key component of protecting water quality is reducing nutrient loading through more accurate prediction of nutrient requirements. CAN’s continual independent and objective advice is increasingly important for development of computer models that provide the biologic basis for predicting farm specific nutrient requirements, which allows economics and excretion rates with alternatives to be accurately predicted. When combined with whole farm planning, nutrient losses into the environment can be reduced.

Fox, D.G., T.P. Tylutki, M.E. Van Amburgh, L.E. Chase, A.N. Pell, T.R. Overton, L.O. Tedeschi, C.N. Rasmussen, and V.M. Durbal. 2000. The Net Carbohydrate and Protein System for evaluating herd nutrition and nutrient excretion. Animal Science Mimeo 213. Department of Animal Science, Cornell University, 130 Morrison Hall, Ithaca, New York 14853-4801.

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Wang, S.J., D.G. Fox, D.J. R. Cherney, L.E. Chase, and L.O. Tedeschi. 2000. Whole herd optimization with the Cornell Net Carbohydrate and Protein Sytem. III. Application of an optimization model to evaluate alternatives to reduce nitrogen and phosphorus mass balance. J. Dairy Sci. 83:2160-2169.