NC1009: Metabolic Relationships in Supply of Nutrients for Lactating Cows (NC-185)
Statement of Issues and Justification
The US dairy industry is a major contributor to the diets of Americans and the economic viability of rural communities. Our long-term goal is to improve the efficiency of milk production and thus promote environmental and economic sustainability in the US dairy industry. Our approach to achieve this goal is to challenge and refine computer-based nutrition systems that will predict the relationship between feed inputs and milk outputs of cattle. To assess the accuracy of these systems, we need adequate quantitative data regarding the absorbed nutrients provided by different diets and the metabolic responses of cows to those nutrients and to regulatory molecules. Our committee is comprised of some of the preeminent dairy scientists in the US with a broad base of specialties that encompass feed analysis; feeding management; ruminal microbial metabolism; intestinal digestion; physiology and metabolism of splanchnic, adipose, muscle, and mammary tissues; molecular and cellular biology; mathematical modeling; and the role of nutrition in health and nutrient partitioning. Our first specific objective is to quantify properties of feeds that determine the availability of nutrients critical to milk production. Our second objective is to quantify metabolic interactions among nutrients that alter synthesis of milk. Our third objective is to use these quantitative relationships to challenge and refine computer-based nutrition systems for dairy cattle. Information from this committee will be disseminated to practicing dairy nutritionists, veterinarians, extension specialists, farmers, and other scientists through regional nutrition conferences, trade and extension publications, electronic media, a national symposium, and applied computer ration balancing programs. Our work will contribute to 1) improved accuracy of feeding standards for dairy cattle and future National Research Council publications on the nutrient requirements of dairy cattle, 2) standardization of analytical methods for feed evaluation, 3) reduced losses of nutrients to the environment from dairy cattle, 4) profitable and environmentally sustainable use of available feedstuffs, and 5) continued supply of affordable, nutritious products for human consumption.
JUSTIFICATION:
The need as indicated by stakeholders. Over 55% of the calcium, 17% of the protein, and 15% of the energy in the US diet are supplied by dairy products; thus, the US consumer is a major stakeholder for the NC-185 committee. Consumers want dairy products that are safe and inexpensive, but increasingly they also want a dairy industry that is environmentally-friendly and that promotes animal well-being. Other stakeholders include practicing nutritionists, veterinarians, and farmers. The needs of these stakeholders have been addressed by the Food Animal Integrated Research group in the FAIR 2002 document. The goals of FAIR 2002 are to strengthen global competitiveness, enhance human nutrition, protect animal health, improve food safety and public health, ensure environmental quality, and promote animal well-being. Because feed inputs are a major determinant of milk yield, cow health, feed efficiency, profitability, and waste output, the work of the NC-185 committee is critical for most of these goals.
The importance of our work. Natural resources are used efficiently when milk production per unit feed and per cow is high (VandeHaar, 1998). To efficiently produce milk, a cow must have a well-developed mammary gland and be able to supply the gland with the nutrients it needs. Nutrition in the first year of life affects mammary gland development, and nutrition around the time of calving and throughout lactation has a major effect on the health, productivity, and efficiency of cows. Feeding for optimal nutrient intake requires not only the provision of the necessary nutrients for milk production but also consideration to the effects of diet on mammary capacity and on appetite, health, and metabolic regulation of the cow. Because feed costs account for half of all costs on a dairy farm, nutrition also significantly impacts farm expenses. The NC-185 committee considers all of these factors for optimal feeding. For example, if we could maintain current milk production while feeding diets with 4 percentage units less total protein, we would decrease N losses to the environment in the US by 470,000 metric tons per year and save US dairy farmers $1 billion per year in feed costs. This type of progress only can be made if we have computer-based nutrition programs that more accurately predict metabolic and production responses of cow to different diets. Without further integrative, multi-faceted research, however, the accuracy of our feeding systems would not improve. Thus, we would not solve our current environmental problems, and we would increasingly rely on imports of dairy products from other countries.
Technical feasibility. The NC-185 committee has a proven track record of making significant impacts in our knowledge dairy cattle nutrition and metabolism and in the way that dairy cattle are fed and managed nationwide. We will continue to use the same general approach that has proven effective in the past-that is to continually challenge and refine our working models of dairy nutrition and metabolism. Computer-based, mechanistic, and quantitative metabolic models are useful in two ways: first, they help us determine critical needs in research and second they enable practical improvements in dairy cow feeding. Critical research needs are determined by using existing data from NC-185 members or conducting new experiments to test model predictions of physiological responses to experimental diets. Examples of such responses include blood urea, milk trans-fatty acids, rumen pH, and milk output. By challenging our working models in this way, we identify shortcomings that then become the basis for developing new testable hypotheses for further experimentation. Results from new experiments are incorporated into the models, and they are challenged again for further refinement. Thus, we continue to build our models so they are more mechanistic, quantitative, and accurate. These qualities enable us to improve practical feeding recommendations for dairy cattle in a variety of environmental and feeding conditions.
Need for Cooperative Work. Important and complex problems require coordinated effort of many personnel. Considerable progress has been made in dairy nutrition, but practical problems remain and no single research group has the skills and resources needed to solve them alone. Individual university programs can solve small aspects of the overall problem well; however, only through cooperation can State Experiment Stations begin to address the sophisticated and complex interactions among feed supply, nutrient use, genetic capability, and milk composition. Our committee is comprised of dairy scientists with a broad base of specialties that encompass feed analysis, feeding management, ruminal microbial metabolism, intestinal digestion, physiology and metabolism of splanchnic, adipose, muscle, and mammary tissues, molecular and cellular biology, mathematical modeling, and the role of nutrition in health and nutrient partitioning. Furthermore, in testing and refining nutrition models for the whole country, we must consider the variation in forages and environment that exist among regions. Thus, we have scientists from every dairy region in the country. This cooperation among stations will have a national impact in efforts to understand the complex interrelationships of nutrient digestion and metabolism in lactating dairy cows and to apply this knowledge to issues of national importance.
Impacts on Science and Other Impacts. This project exemplifies the proven effectiveness of the cooperative regional approach. As detailed in the "Related Current and Previous Work" section below, results of this cooperative effort have become benchmarks of scientific progress and have led to practical feeding recommendations used worldwide. Project Leaders for the NC-185 regional project have received numerous awards for research, both basic and practical, from the American Dairy Science Association, the American Society of Animal Sciences, and industry groups. Most of the Project Leaders are in continuous demand as speakers for scientific and industry conferences in nutrition. The impact on basic and practical nutrition from Project Leaders has been profound in the areas of starch and protein chemistry and nutrition, feed processing, nutrient metabolism, and lactation biology. Most recently, a major impact of our group was its contribution to the 2001 version of the National Research Councils (NRC's) Nutrient Requirements of Dairy Cattle. Four of the 10 scientists on the NRC panel were from the NC-185 committee, and a significant portion of the data used in the latest edition came from NC-185 committee members. Thus, the NC-185 committee has had a major impact on improving the biological, economical, and environmental efficiency of the US dairy industry.
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