Duration: 10/01/2002 to 09/30/2007

Administrative Advisor(s):

NIFA Reps:

Non-Technical Summary

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.

Related, Current and Previous Work

The amount and profile of absorbed nutrients in dairy cattle are primarily a function of rumen fermentation and intestinal digestion. Rumen fermentation enables ruminants to effectively digest fiber, make microbial protein, and produce volatile fatty acids for absorption. Feed particles and microbes that escape the rumen can be digested in the small intestine to produce amino acids, monosaccharides, and lipids for absorption.

The chemical and physical properties of feeds determine the availability of nutrients critical to the production of milk and milk components in a variety of ways. For example, the chemical composition (including total protein, nonprotein nitrogen, amino acid balance, organic acids, lipids, fiber, and non-fiber carbohydrate) dictates directly the availability of nutrients to support rumen microbial growth and the absorbed nutrients available to the animal to support milk synthesis. The physical properties of feeds, either inherent in the plant structure or altered by various processing methods, alters degradability in the rumen, and thus determines the proportion of feed fermented and used for rumen microbial growth and the proportion that passes to the small intestine. The goal in feeding cattle is to find the optimal combination of chemical and physical properties that provides the proper amount and balance of absorbed nutrients from ruminal fermentation and postruminal digestion. This goal is a major challenge because of the tremendous variety of feedstuffs available, their associative effects, and the rapidly changing nutrient requirements of a cow around the time of parturition.

Dietary carbohydrate fractions differ in the profiles of glucogenic and lipogenic metabolites they yield from ruminal and intestinal digestion (Marounek et al., 1985; Strobel and Russell, 1986). The amount and types of carbohydrates also impact rumen pH, which, in turn, alters fermentation and can alter the yield of nutrients for absorption (Strobel and Russell, 1986). Rapidly fermenting carbohydrates will likely have a greater yield of fermentation products because of a greater extent of ruminal fermentation than slowly fermenting materials, given similar rates of passage. Thus the various carbohydrate fractions have differential effects on the yield and composition of milk (Broderick et al., 2000; Leiva et al., 2000; Mansfield et al., 1994; Solomon et al., 2000). Study of the effects of specific non-fiber carbohydrates on animal performance has been difficult because feasible methods for feed analysis are lacking. Recent improvements in methods will allow more accurate prediction of optimal amounts and ruminal availability of non-fiber carbohydrates for efficient production of milk and milk components (Hall et al., 1999).

The amount and balance of absorbed amino acids is a prime determinant of milk protein synthesis. This availability of amino acids, in turn, is a function of the amount of feed protein which passes undegraded through the rumen to the small intestine and the amount of ruminally synthesized microbial protein that reaches the small intestine. Microbial protein typically has a better amino acid profile than many feed proteins relative to milk protein. Microbial protein yield is a function of the amount of rumen degraded protein and the amount of organic matter fermented (Firkins, 1996). Thus, microbial protein yield varies by source of carbohydrate and protein (Hall and Herejk, 2002), and rate of fermentation (Nocek and Russell, 1988).

Research summarized from over 90 studies, of which >70 were done by cooperators of the NC-185 project, has shown little benefit of replacing soybean meal with protein sources higher in rumen undegradable protein (RUP) (Baldwin, 1995; Santos et al., 1998). This result was not entirely unexpected because absorbed protein is a function of not only RUP, but also its amino acid profile and the flow of microbial protein to the duodenum. In some of these studies, control cows were fed sufficient total protein so that additional RUP had no benefit. In some, the RUP source was lacking in the two most limiting amino acids-methionine and lysine. Finally, the types and amounts of carbohydrate in the diet also impact the benefit of high RUP feeds (Mertens et al., 1994). Thus, in some cases, the increased milk yield with increased RUP may be related to the feeding of more slowly fermented starch, or of sugars and soluble fiber (notably pectin).

Synthesis of milk and milk components is a function of both the synthetic potential of the mammary gland and the supply of metabolites to the mammary gland. Supply of metabolites comes from dietary components, some of which are modified in other tissues, and from mobilization of body lipids and amino acids. There is an interaction between mobilization of body tissues, the supply of dietary nutrients and the milk production potential of the cow (Baldwin, 1995) such that increased dietary supply of nutrients alters mobilization of body tissues. Metabolic intermediates may even interact with different classes of nutrients and milk components. Several stations have been studying these interactions by examining the interaction of prepartum and postpartum diets (KS, PA, WA, MI, IN). Data from PA collected as part of this project indicates that tissue amino acids are mobilized for use as gluconeogenic precursors, and thus the fate of mobilized body protein can be lactose in milk (Vallimont et al, in press). This mobilized protein may be mostly myofibrillar protein, and increases in dietary glucogenic precursors may have little effect on altering body protein mobilization (Plaizier et al 2000). This finding is consistent with recent data showing that feeding increased dietary protein prepartum increased milk production postpartum, but did not alter mobilization of body protein (McNamara et al., 2001). Work at KS also shows that feeding more protein may benefit milk production. Recent data from WA showed that improving the amino acid balance of cows prepartum with methionine seemed to decrease the loss of body muscle postpartum (Citron et al., 2000).

Protein nutrition during lactation also has dramatic effects on milk production, as has long been known. In the past 5 years, major advances have been understanding amino acid nutrition of dairy cows. In particular, work at NH, WI, and IL has shown that methionine is generally the most limiting absorbed amino acid in lactating cows and that supplemental methionine can significantly increase milk protein production and efficiency of dietary protein use (NRC, 2001). However, even when we expected protein to be limiting for milk production, the response to additional protein or additional methionine is not as high as expected. In other words, the efficiency of capturing additional protein is often only 20% or less-perhaps because it is being used as a glucogenic substrate (Hanigan et al., 1998).

Major advancements have occurred in our knowledge of the interaction of metabolism and the endocrine system. Studies at AL, IN, and MI, in collaboration with other NC-185 members, have illustrated the role of nutrition in the IGF-I system of dairy cattle. Studies at IA have illustrated the role of glucagon in lipid metabolism and shown its potential benefit as a treatment for fatty liver (Hippen et al., 1999).

If we are to improve the accuracy and precision of predicting nutrient use, we must continue to improve mechanistic, dynamic models of metabolism. Publications of work of NC-185 committee members individually and in collaboration served as a major source of the new information used in developing the latest version of the Nutrient Requirements of Dairy Cattle by the National Research Council (NRC, 2001). This version document introduced many more mechanistic elements to provide a better description of nutrient use in dairy cattle. However, the document also pointed out many of the shortcomings in our current knowledge base. The new version is limited especially in predicting dietary nutrient interactions, which consequently hamper our ability to predict rumen microbial metabolism and microbial protein yield and therefore responses to rumen-undegraded protein, carbohydrate, and fat supplements. Other significant limitations are the ability to predict short term versus long-term nutritional responses and changes in body fat and protein use. Modeling of the metabolism of the lactating dairy cow will allow for evaluation of these interactions.

The most comprehensive mechanistic and dynamic model of metabolism in the dairy cow is called 'Molly', developed at CA with inputs from most NC-185 members (Baldwin, 1995). Members of this project also have been instrumental in developing the new NRC model (NRC, 2001), which serves as the standard for dairy ration formulation and evaluation in the US. Members of NC-185 also have developed more applied models, such as the widely-used "Spartan" computer program from MI. These different computer nutrition programs are currently in use for predicting nutrient requirements and productivity of lactating dairy cows. While all of these systems are soundly based on available data, all have weaknesses in the areas defined by Objectives 1 and 2. The rate of degradation of feedstuffs, the effect of various dietary carbohydrates on rumen fermentation and microbial protein synthesis, and quantitative data on metabolic interchanges among nutrients and body tissues limit the accuracy of these systems (Baldwin, 1995). New collaborative efforts by the NC-185 project are needed to remove these inaccuracies.

An evaluation of the current working version of Molly indicated that, while it is quite impressive in describing milk component output on standard diets, it lacked sensitivity to predict body protein and fat mobilization or deposition during early lactation. (Sage et al., 2000; Citron et al., 2000). Molly seems especially limited in its ability to describe the rapid changes in nutrient use that occur in early lactation and in predicting physiological responses to very high feed intakes or diets with atypical amino acid, fiber, or starch contents. Thus, quantitative data are still needed on the supply of milk component precursors available under these different metabolic and nutritional conditions, such as early lactation. Data also are needed on the metabolic interconversions of nutrients, such as the use of amino acids for gluconeogenis and thus milk lactose synthesis, and the partitioning of body fat and fat derived from the diet or lipogenesis for milk fat synthesis. These data will enable further refinement of current nutrition recommendations and aid in interpretation of feeding experiments.

A search of the CRIS database found 1580 research projects related to dairy production. Of these, 87 were associated with members of the NC-185 project. Most of the remainder of the projects are outside of the scope of the NC-185 effort, and deal with topics such as genetics, disease, hormones, vitamin and mineral nutrition, heifer management, and other management systems. There are five multistate projects that are closely related to the NC-185 project. They are:

1. NE-148 "Regulation of nutrient use in food-producing animals", which addresses hormonal regulation of nutrient use in growth and lactation for dairy and other livestock.
   
2. W-181 "Modifying milkfat composition for enhanced manufacturing qualities and consumer acceptability", which focuses on milkfat production and processing.
   
3. NE-132 "Environmental and economic impacts of nutrient management of dairy forage systems", which focuses on strategies for managing and feeding forages to optimize their use on dairy farms.
   
4. S-299 "Enhancing production and reproductive performance of heat-stressed dairy cattle", which focuses on nutritional and environmental strategies to overcome heat stress.
   
5. NC-119 "Management systems for improved decision making and profitability of dairy herds", which focuses on management systems for the entire dairy farm but especially on young stock.

All of these projects have some overlap with the NC-185 project, and there are some cooperators who contribute to more than one of these projects. These various areas cannot and should not be fully separated, but each in itself encompasses a major scientific challenge. Joining the efforts of the NC-185 committee with these other efforts would not be feasible or beneficial. As a result of the CRIS search, we have identified one new potential cooperator (NY) who will be asked to join the committee, pending its approval.

Objectives

1. To quantify properties of feeds that determine the availability of nutrients critical to milk production. 1a) To quantify effects of feed carbohydrates, proteins, and lipids on rumen microbes and subsequent effects on nutrient supply to the animal.; 1b) To improve and standardize methods for evaluating the nutritional quality of feeds.
   
2. To quantify metabolic interactions among nutrients that alter synthesis of milk. 2a) To quantify relationships in partitioning of nutrients between body tissues and milk synthesis. 2b) To quantify metabolic responses in cows of differing milk production potential.
   
3. To use these quantitative relationships to challenge and refine computer-based nutrition systems for dairy cattle.
   
4. 
   

Methods

Objective 1. To quantify properties of feeds that determine the availability of nutrients critical to milk production.

The quantitative relationships among non-fiber carbohydrate degradability and type, protein degradability and type, and milk and milk component production will be explored. The effects of N source, carbohydrate source, and pH on yields of microbial protein, a-glucan, and volatile fatty acids and on the extent of fiber fermentation will be quantified in in vitro fermentation studies using purified substrates (sucrose, corn starch, and isolated bermudagrass NDF) and mixed ruminal microbes (FL, MO). These relationships will be verified in continuous culture systems and in feeding studies with lactating cows measuring milk production as well as rumen and plasma metabolites (FL, PA). Working together, NH and MN will quantify nitrogen fractions, ruminal digestion rates of the B nitrogen fraction, and intestinal digestibility of rumen-undigested protein in a variety of feedstuffs, with particular emphasis on those feeds on which there is limited data. Data on carbohydrate and protein degradability is needed not only to increase the utility of the current models in predicting nutrient supply, but also to benefit the next NRC publication.

Sorting of feeds by cows has the potential to greatly alter the nutrients available to support milk production. Sorting in free-stall and tie-stall environments will be compared (WI) using a switchback design and marker techniques to measure sorting for cows in free-stalls. The effects of amount and source of protein (solvent-extracted soybean meal vs animal protein and protected soybean meals) on passage of nutrients (microbial protein, feed protein, amino acids, nonstructural carbohydrate, starch, fiber, lipid) to the small intestine and on milk production will be determined (IL). Improved measurement of ruminal passage rate (OH) should help in the integration of these data into kinetic models used in several computer systems.

The combined analysis of fecal purines, volatile fatty acids, and pH will be examined as a method for measuring large intestinal fermentation in lactating cows (WI). Combining these quantitative estimates with rRNA-sequence based population descriptions will give an indication of the types of substrates (starch vs. fiber) being fermented in the large intestine. Measuring large intestinal fermentation is a good indicator of the completeness of rumen fermentation as well as determining the ability of the large intestine to contribute to animal energy needs and to modify the volatility of excreted nitrogen. Such measures should be useful as diagnostics in practical dietary management.

The effects of pH during grain extrusion on starch and protein availability will be studied using in vitro (MN) and in vivo (UT) methods. The long-term impact of this research will be to develop a technique to increase utilization of protein from soybeans in dairy cows and minimize the nitrogen excretion in the environment. Ohio researchers are working on improved marker systems for the measurement of microbial protein flow to the duodenum and recycling within the rumen, with the ultimate goal of reducing ruminal losses of ammonia-nitrogen.

Objective 2: To quantify metabolic interactions among nutrients that alter synthesis of milk.

The proposed experiments will focus on enhancing our knowledge of body tissue mobilization and the metabolic interchange between nutrient classes. The effects of dietary protein and amino acid supply on body protein mobilization will be determined. Use of tissue amino acids for glucose synthesis in response to both onset of lactation and altered gluconeogenic precursor supply will be quantified. The role of dietary fat, both level and source, and metabolic responses to specific fatty acids, also will be evaluated in relation to both milk fat content and metabolic and regulatory responses at both the genomic and endocrine level.

Experiments will be done at PA with analytical cooperation from AL on altering supply of propionate, a glucose precursor, and its effects on amino acid and body protein mobilization by using indirect methods of assessing body protein use. These experiments will use stable isotope labeled metabolic intermediates to provide quantitative data on metabolic interchanges. Experiments on amino acid and energy balance in early lactation will be done by WA and NH, providing quantitative data to further refine the models currently in use. Milk production will be measured, so that partitioning of nutrients between body tissues, in this case protein, and milk can be measured quantitatively. In addition, interconversions of butyrate, and acetate will be determined. Glucose kinetics will be measured concurrently with the VFA isotope infusion to determine propionate uptake by the liver. Modeling of liver and rumen function will be done. These experiments will be done from two weeks prepartum to two weeks postpartum at PA.

Nutrient gene interactions that enhance milk production and animal health and quantitative relationships between expression of genes controlling liver metabolism and milk production and optimal animal health in lactating dairy cattle will be investigated with the cooperation with IN and PA. Liver biopsy samples collected at IA, PA, and IN will be processed and analyzed at IN for expression of candidate genes and genes clusters that respond to nutritional regimens, physiological state, and metabolic disease state. At AL, experiments will be conducted evaluating gene expression associated with skeletal muscle protein degradation in the transition period in cows fed varying levels of dietary nitrogen. Gene expression in liver and mammary gland of heifers fed high or low energy diets will be assessed at MI.

With the cooperation of MN, ND is planning to conduct experiments on the effect of linoleic acid-containing oilseeds on production response parameters in lactating dairy cows. Similar experiments will be conducted by SD, who also will measure transport of fatty acids in the blood. These experiments will evaluate plasma fatty acid content and source and the effect of dietary linoleic acid on mobilization of body fat.

The effect of glucagon on fat metabolism in the liver of dairy cows will be evaluated at IA, with the cooperation of SD and IN. Emphasis will be placed on dosage and timing of glucagon administration. The potential of ultrasound to evaluate fatty livers will be further refined and evaluated as well. Glucagon administration will be evaluated as to its effects on body fat mobilization as indicated by hepatic fat content and on milk production

Genetic potential of cows for milk production will be included in the data analysis from most experiments to account for this effect on responses to dietary alterations. At NH, with the cooperation of WA, experiments will be conducted using graded and defined infusions of essential amino acids, while maintaining other amino acids at adequate amounts, to evaluate optimal amounts of essential amino acids absorbed per day in relation to potential milk production. These experiments will be designed so as to ensure that the data collected will be useful in the Molly model.

South Dakota (SD), with the cooperation of MN, UT, and WA, will evaluate the effects of different long-chain fatty acids (different proportions of conjugated-linoleic acid, transvaccenic acid, and omega-3 fatty acids) added to the diet on fatty acid metabolism and milk fat production of dairy cattle. Milk production and transport and partitioning of nutrients also will be measured, which contributes to Objective 2a. The effects of these fatty acids added to the diets of periparturient dairy cows on hepatic metabolism, gluconeogenesis, and endocrine regulation of hepatic metabolism will also be measured in experiments conducted at SD. Cooperating stations will be IA and IN.

Experiments evaluating the effect of pre-pubertal growth rate on subsequent milk production, and the interaction of growth rate and genetics on their effects on milk production potential will be conducted at MI.

Objective 3: To use these quantitative relationships to challenge and refine computer-based nutrition systems for dairy cattle.

Several different computer-based nutrition systems are currently in use for predicting nutrient requirements and productivity of lactating dairy cows. Members of the NC-185 project have been instrumental in developing both the "Molly" model in CA (Baldwin, 1995) and new NRC model (National Research Council, 2001), as well as the "Spartan" model from MI. All of these systems are based soundly on available data, but all have weaknesses in the areas defined by Objectives 1 and 2.

Experiments conducted under Objectives 1 and 2 will address deficiencies in the database. These experiments will use common feedstuffs, designs, and response variables when possible. Dietary analyses also will be coordinated so as to provide accurate descriptions of nutrient supply for absorption. The resulting data will be used to both challenge and refine the systems, especially Molly. The objective is to both refine the models and maintain an active group of scientists with expertise in the area of model development. Using models properly allows for more precise experimental design, speeds up the rate of progress and allows for production applications of research results to make an impact more quickly. Three stations, CA, WA, and MI, will be involved in efforts to systematically challenge each of the models widely in use in the U.S. to ascertain their strengths and weaknesses. If the NC-185 project is approved, we plan to add a member from NY to also include the Cornell model in this effort. Approaches from one model then may be used to strengthen another model. This "cross-fertilization" will benefit all of the models currently in use.

Measurement of Progress and Results

Outputs

• Quantitative data will be generated to allow for refinement of current models of dairy cow metabolism and to provide data on areas where none currently exists. Specific dietary conditions that alter gene expression associated with metabolic alterations will also be identified, as will the effect of the genetic potential of the dairy cow. The refinement of metabolic models will directly lead to new technologies (such as computer programs) or new management practices for use on commercial farms.

Outcomes or Projected Impacts

• Refinement of the current nutrition programs will allow more exact formulation of diets for lactating dairy cattle. Feed costs and environmental impacts from excess dietary nutrients will be reduced for dairy farmers. Consumers will benefit from both reduced environmental impacts of food production and lower prices due to increased supply and lower input costs. Consumers will also benefit from possible alteration of the fatty acid content and composition of milk fat, resulting in a healthier diet.

Milestones

(0):three years of approval of this project, sufficient quantitative data should be developed to allow for incorporation into the current metabolic models. By year 5, refined models should be available and information on dietary alteration of milk fat composition and content and on dietary effects on gene expression will be disseminated.

(0):0

Projected Participation

View Appendix E: Participation

Outreach Plan

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, and applied computer ration balancing programs. We also are planning a national symposium on the latest findings of our committee in conjunction with the American Dairy Science Association for 2004.

Organization/Governance

The technical committee will have a chair, secretary, and regional administrative advisor. The executive committee will consist of these three persons and the previous chair and will be the official nominating body. The chair and secretary will be elected by the voting members from within their ranks. The chair is responsible for planning and conducting the annual meeting, for submission of the project annual report, and for facilitating and ensuring effective communication and cooperation among participants. The secretary is responsible for recording minutes and distributing them prior to the chair preparing the annual report. Individual station members are responsible for preparing brief annual reports and distributing them to other participants two weeks prior to the annual meeting. Individual station members are to share data directly with CA, WA, and MI in a format suitable for incorporation into the appropriate computer systems. Additional committees, composed of voting and non-voting members, may be appointed as needed to solve particular technical problems, to assist in communication within the project, or to report project findings to other interested parties.

Literature Cited

Baldwin, R. L. 1995. Modeling Ruminant Digestion and Metabolism. Chapman & Hall, New York.

Broderick, G. A., N. D. Luchini, W. J. Smith, S. Reynal, G. A. Varga, and V. A. Ishler. 2000. Effect of replacing dietary starch with sucrose on milk production in lactating dairy cows. J. Dairy Sci. 83(Suppl. 1):248 (Abstr.).

Citron, T. L., J. J. Sage, J. G. Phillips, and J. P. McNamara.2000. Indirect measurement of muscle protein degradation in lactating dairy cattle to challenge a metabolic models ability to describe body protein usage. J. Dairy Sci. 83 (Suppl. 1):13.

Firkins, J. L. 1996. Maximizing microbial protein synthesis in the rumen. J. Nutr. 1 26:1347S-1354S.

Hall, M. B. and C. Herejk. 2001. Differences among carbohydrates in yields of crude protein from in vitro fermentation with mixed ruminal microbes. J. Dairy Sci. Accepted.

Hall, M. B., W. H. Hoover, J. P. Jennings, and T. K. Miller Webster. 1999. A method for partitioning neutral detergent-soluble carbohydrates. J. Sci. Food Agric. 79:2079-2086.

Hanigan, M. D., J. P. Cant, D. C. Weakley, and J. J. Beckett. 1998. An evaluation of postabsorptive protein and amino acid metabolism in the lactating dairy cow. J. Dairy Sci. 81:3385-3401.

Hippen, A. R., P. She, J. W. Young, D. C. Beitz, G. L. Lindberg, L. F. Richardson, and R. W. Tucker. 1999. Alleviation of fatty liver in dairy cows with 14-day intravenous infusions of glucagon. J. Dairy Sci. 82:1139-1152.

Leiva, E., M. B. Hall, and H. H. Van Horn. 2000. Performance of dairy cattle fed citrus pulp or corn products as sources of neutral detergent-soluble carbohydrates. J. Dairy Sci. 83:2866-2875.

Mansfield, H. R., M. D. Stern, and D. E. Otterby. 1994. Effects of beet pulp and animal by-products on milk yield and in vitro fermentation by rumen microorganisms. J. Dairy Sci. 77:205-216.

Marounek, M., S. Bartos, and P. Brezina. 1985. Factors influencing the production of volatile fatty acids from hemicellulose, pectin and starch by mixed culture of rumen microorganisms. Z. Tierphysiol. Tierernahg. u. Futtermittelkde. 53:50-58.

McNamara, J. P., J. J. Sage, T. L. Citron, and G. J. Phillips. 2001. Adaptations in amino acid concentrations, body fat, and body protein in dairy cattle fed varying amounts of protein in the transition period. J. Dairy Sci. 84 (Suppl.1): 294.

Mertens, D. R., G. A. Broderick, and R. Simons. 1994. Efficacy of carbohydrate sources for improving utilization of N in alfalfa silage. J. Dairy Sci. 77(Suppl. 1):240 (Abstr.).

National Research Council. 2001. Nutrient requirements of dairy cattle, 7^th edition. National Academy Press, Washington, DC.

Nocek, J. E., and J. B. Russell. 1988. Protein and energy as an integrated system. Relationship of ruminal protein and carbohydrate availability to microbial synthesis and milk production. J. Dairy Sci. 71:2070-2107.

Plaizier, J. C., J. P. Walton, A. Martin, T. Duffield, R. Bragg, P. Dick, and B. W. McBride. 2000. Short Communication: Effects of monensin on 3-methylhistidine excretion in transition dairy cows. J. Dairy Sci. 83:2810.

Sage, J., J. Phillips, T. Citron, and J. McNamara. 2000. Challenging a mechanistic model of dairy cattle metabolism to describe changes in body fat of high producing dairy cattle fed various diets during early lactation. J. Dairy Sci. 83 (Suppl. 1):13.

Santos, F.A.P., J.E.P. Santos, C. B. Theurer,C.B., and J. T. Huber. 1998. Effects of rumen-undegradable protein on dairy cow performance: A 12-year literature review. J. Dairy Sci. 81:3182-3213.

Solomon, R., L. E. Chase, D. Ben-Ghedalia, and D. E. Bauman. 2000. The effect of nonstructural carbohydrate and addition of full fat extruded soybeans on the concentration of conjugated linoleic acid in the milk fat of dairy cows. J. Dairy Sci. 83:1322-1329.

Strobel, H. J., and J. B. Russell. 1986. Effect of pH and energy spilling on bacterial protein synthesis by carbohydrate-limited cultures of mixed rumen bacteria. J. Dairy Sci. 69:2941-2947.

Vallimont, J.E., G.A. Varga, A. Arieli, T. W. Cassidy, and K. A. Cummins. 2001. Effects of prepartum somatotropin and monensin on metabolism and production of periparturient Holstein dairy cows. J. Dairy Sci. (in press)

VandeHaar, M.J. 1998. Efficiency of nutrient use and relationship to profitability on dairy farms. J Dairy Sci 81:272-282.

Attachments

Land Grant Participating States/Institutions

AL, AZ, CA, IA, IL, KY, MD, MI, MN, MO, ND, OH, OR, PA, SD, VA, WA, WI

Non Land Grant Participating States/Institutions

J.D. Heiskell & Co., other, USDA-ARS/Wisconsin