ISSUES

The US dairy industry is a major contributor to the diets of Americans and the economic viability of rural communities. With current dietary patterns in the US, dairy products supply about 11% of the calories, 17% of the protein, 52% of the calcium, 51% of the vitamin D, 29% of the vitamin A, 28% of the vitamin B12, and 17% of the zinc in diets of Americans over the age of 2 (among other essential nutrients). The industry provides 3.3 million jobs and total economic activity of more than $750 billion annually in the US. Despite these important contributions, there are also significant challenges to the sustainability of the industry, including concerns about the environmental footprint of dairy production, animal well-being, and rising input costs.

Our long-term goal is to improve the efficiency of milk production as well as cow health and longevity, and thus promote environmental and economic sustainability of the US dairy industry. Our approach to achieve this goal is to systematically identify biological and nutritional management processes that will provide the greatest improvement and to concentrate our collaborative research efforts there. This is done partly through the construction, evaluation, and refinement of computer-assisted bio-mathematical models that describe the metabolic relationships between feed inputs and milk outputs of cattle. We use the terminology “precision feeding systems” to reflect the goal of being able to efficiently feed dairy cows that widely differ in genetics, environment and diets. Although dairy producers large and small feed dairy cattle in a wide variety of ways, a major goal is to be precise in meeting the needs of their cows across those diverse systems.

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 and animal genotypes and phenotypes (genomics, transcriptomics, proteomics, metabolomics) into traditional livestock nutritional science 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. Likewise, increasing knowledge of how nutrition impacts animal health opens an avenue for dairy nutritionists to address sustainability challenges linked to the short productive life of US dairy cattle. These developments hold 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 gaps in knowledge steadfastly in the last 40 years, including the last 5, and the research and outreach done by this group continues to improve the understanding and efficiency of dairy production. A cornerstone of the recent achievements is the 2021 publication of the NASEM Nutrient Requirements of Dairy Cattle that was written by a committee with more than half of members who are current or retired NC-2040 members. This publication is the go-to resource for definitive information on dairy cattle nutrition, and the contributions of this committee in shaping that resource are among our greatest impacts. 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. The outcomes of this work were essential in the 2021 NASEM publication; however, much remains to be done. For reasons given in the previous paragraph, improvements in designing, conducting and interpretating complex research, 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. With these changes, the committee has identified new approaches and set new goals, all under the umbrella of feeding and metabolism of dairy cattle.

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

The overarching goal is to do sound, collaborative research directed toward identifying specific biological concepts and processes that can be applied to improve dairy cattle feeding. Our work contributes to 1) improved accuracy of feeding standards and nutrient requirement predictions for dairy cattle, 2) standardization of analytical methods for feed evaluation, 3) reduced losses of nutrients and greenhouse gasses to the environment from dairy cattle, 4) profitable and environmentally sustainable use of available feedstuffs, 5) continued expansion into new areas of  integrative biology involving nutrition and 6) continued supply of affordable, nutritious products for human consumption.

JUSTIFICATION:

The Need as Indicated by Stakeholders. Approximately 52% of the calcium, 17% of the protein, and 11% 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 such as conjugated linoleic acids, and the expertise of the NC-2040 committee is well aligned with objectives to increase delivery of bioactive compounds into milk. Primary direct stakeholders include other scientists, practicing nutritionists, veterinarians, and farmers. Feed inputs are a major determinant of milk yield, cow health, feed efficiency, profitability, and waste output, and the work of the NC-2040 committee is critical to meet stakeholder needs.

Importance of the Work. Natural resources are used most efficiently when milk production per unit feed and per cow is high. 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 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. Computer-based, mechanistic, and quantitative metabolic models are useful in two ways: first, they help us determine critical needs in research and secondly, 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 collaborative 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.

Advantages for Doing the Work as a Multistate Effort.  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 environment, feed supply, nutrient use, microbial ecosystems, animal genetics, 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, 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 and managing the complex interrelationships of nutrient digestion and metabolism in lactating dairy cows.

Likely 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 in our discipline and have led to practical feeding recommendations used worldwide. As noted above, this group provided a major contribution to the 2021 version of the National Academies of Sciences, Engineering, and Medicine’s (NASEM's) Nutrient Requirements of Dairy Cattle. Eight of the 12 scientists on the NASEM panel were current or former NC-2040 committee members, and a significant portion of the data used in the latest edition was generated through the collaborative work of NC-2040 committee members. 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.