NC2040: Metabolic Relationships in Supply of Nutrients for Lactating Cows

(Multistate Research Project)

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The US dairy industry is a major contributor to the diets of Americans and the economic viability of rural communities as well as many states. Our long-term goal is to improve the efficiency of milk production, cow health and longevity, and thus promote environmental and economic sustainability in the US dairy industry. Our approach to achieve this goal is to systematically identify those biological and nutritional management processes that will provide the greatest improvement and to concentrate our research efforts there. This is done partly through the construction, challenge and evaluation of computer-assisted bio-mathematical models that describe the metabolic relationships between feed inputs and milk outputs of cattle. We have chosen the term precision feeding systems in this revision to reflect the goal of being able to feed dairy cows that widely differ in genetics, environment and diets, not to reflect any particular methodology or feed delivery system. Although dairy producers, large and small, feed in a large variety of ways, a major goal is to be precise in meeting the needs of their cows.


Improvement in animal and resource efficiency is slowed by a lack of clear research priorities addressing the most critical areas. This is due to a combination of factors, including: lack of quantitative data regarding absorbed nutrients and the metabolic responses of cows to those nutrients; a lack of integration of existing data into bio-mathematical models that will point out areas of greatest need; and a lack of real and enthusiastic support in the research and funding communities for cooperative, large-scale, integrated research work. In addition, integration of recent discoveries concerning genetic regulation, animal genotypes and phenotypes (genomics, gene arrays, proteomics, metabolomics), into traditional nutritional science in animal agriculture has been slow. Recent technological advancements and an appreciation for the importance of genotype in nutrient use by dairy nutritionists are now increasing the pace of that integration. This holds great promise for quantum improvements in efficiency (10 to 15 % on a herd basis as opposed to the traditional incremental increases).


Our committee has addressed these lacks in knowledge steadfastly in the last 35 years, including the last 5, and the research and outreach done by this group continues to improve the understanding and efficiency of dairy production. The 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 major organ systems; molecular and cellular biology; mathematical modeling; and the role of nutrition in health and longevity of animals. In the revision beginning in 1987, a conscious effort was made to plan and conduct experiments to provide data to improve research and practical nutritional models. Research done since then has come a long way to do that, however much remains to be done. For reasons given in the previous paragraph, improvements in complex research design, conduct and interpretation, including integrating information into model systems, has been slow. Yet this committee has continued to do excellent scientific work in practical and basic dairy nutrition. New additions to the committee in the past 5 years have maintained our traditional strength in applied dairy nutrition while also enhancing expertise in rumen microbiology, molecular biology, and quantitative analysis. The committee is not dying off and wrapping up work, but rather changing and setting new goals, all under the umbrella of feeding and metabolism of dairy cattle.


We have retained our title and objectives as these are still closely reflect our collective mission. Our first specific objective is to quantify properties of feeds that determine the availability and utilization of nutrients critical to milk production. Our second specific objective is to quantify metabolic and molecular interactions that alter synthesis of milk components. Our final objective is to use this knowledge of feed properties and metabolic and molecular quantitative relationships to challenge and refine precision feeding systems for dairy cattle.


This committee has had a strong history in both basic biological research and practical application, and we intend to maintain that breadth. The overarching, ultimate goal is to do sound research directed toward finding out the most specific biological concepts and processes, and to apply that knowledge to the improvement of dairy cattle feeding in the practical work. Results from work done by 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, frequent national symposia, and applied computer ration balancing programs. Our work contributes 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, 5) continued expansion into new areas of genetics and nutrition and integrative biology and 6) continued supply of affordable, nutritious products for human consumption.


JUSTIFICATION:


The need as indicated by stakeholders. Approximately 50% of the calcium, 20% of the protein, and 10% of the energy in the US diet are supplied by dairy products; thus, the US consumer is a major stakeholder for the NC-2040 committee. Consumers want dairy products that are safe and inexpensive, but increasingly they also want an environmentally friendly dairy industry that promotes animal well-being. Recently, attention has been given to bioactive molecules in milk (in addition to Calcium) such as conjugated linoleic acids. Yet at its core the NC 2040 committee functions to do basic and applied research on the feeding and nutritional biology of dairy cattle. Major stakeholders include other scientists, 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-2040 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 (Baldwin, 1995; 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-2040 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 300,000 metric tons per year and save US dairy farmers $540 M per year in feed costs.  [This calculation assumes 1) dry matter intake is 20 kg/d, 2) US cow population is 9.2 M, 3) efficiency of milk protein production (milk protein/protein intake) is 0.3, and 4) cost of crude protein is $0.20/kg.]  This type of progress only can be made if we take an integrated approach, with the use of mechanistic bio-mathematical models that accurately describe metabolism and production of cows.


Technical feasibility. This committee has a record of making significant impacts in our knowledge of dairy cattle nutrition and metabolism and in the way that dairy cattle are fed and managed nationwide. We use the same approach that has proven effective in the past: that is to challenge and refine our 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-2040 members or conducting new experiments to test model predictions of physiological responses to experimental diets. Examples of such responses include, rumen pH, microbial growth and function; alterations in gene expression and hormonal release of organs such as the adipose tissue; and alterations in milk fatty acid compositions. 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. Only through cooperation can State Experiment Stations address the 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, endocrine regulation, molecular and cellular biology, and mathematical modeling. 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. In addition, the explosion of new information in genomics, gene expression, gene array work, metabolomics and proteomics requires that we integrate this knowledge into our understanding of metabolic efficiency. Cooperation among stations is required to deal with this information and to solve problems, and will have a national impact in understanding the complex interrelationships of nutrient digestion and metabolism in lactating dairy cows and to apply this knowledge.


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-2040 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. This group provided a major contribution to the 2001 version of the National Research Council’s (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-1009 committee members. In 2005, the group presented a symposium at ADSA/FASS on regulation of nutrient use in dairy cattle (references are in bibliography). Currently, a committee is revising the NRC Nutrient Requirements of Dairy Cattle, and 7 of the 13 members are current or former members of NC2040. Thus, this committee has had a major impact on improving the biological, economical, and environmental efficiency of the US dairy industry. We continue to recruit and support young scientists to keep the committee current and effective year to year.

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