NC2040: Metabolic Relationships in Supply of Nutrients for Lactating Cows (NC-1009)
(Multistate Research Project)
NC2040: Metabolic Relationships in Supply of Nutrients for Lactating Cows (NC-1009)
Duration: 10/01/2013 to 09/30/2018
Statement of Issues and Justification
The US dairy industry continues to be major contributor to the diets of Americans and the economic viability of rural communities as well as for many states. Our long-term goal is to improve the efficiency of milk production, cow health and longevity, and thus promote continued food sufficiency, environmental sustainability, and economic sustainability in the US dairy industry. Although we have made progress in improving efficiency and sustainability of the dairy industry, there is still much knowledge that could be gained that will lead to further progress. One major lack is in the integration of disciplinary knowledge, including new methods and knowledge from genomic research, in order to make better recommendations on nutritional, reproductive and genetic management of dairy cattle.
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 through the generation of new basic and applied knowledge and the integration of that knowledge by construction, challenge and evaluation of computer-assisted bio-mathematical models that describe the metabolic relationships between feed inputs and milk outputs of cattle. This approach leads directly to new and updated field application tools such as the NRC nutrient requirement models. Future tools will encompass interconnections between nutrition, housing, animal welfare, genetics, reproduction, environmental sustainability and milk production and quality.
This revision reflects the goal of being able to feed dairy cows that widely differ in genetics and are exposed to a wide range of management and environment conditions using a wide range of ingredients subject to volatile and increasing input costs and milk returns. Although dairy producers, large and small, feed in a variety of ways, a major research and application goal is to be more precise in meeting the needs of their cows. This is especially important given the continued increase in volatility and variation in supply and prices of feedstuffs and the long-term needs to double food production in the next 40 years. Although much progress has been made in defining nutrient availability and metabolism, there is still a lack of quantitative data regarding absorbed nutrients and the metabolic responses of cows to those nutrients, and a lack of integration of existing data into bio-mathematical models that will point out areas of greatest need. An added challenge for the future is the need to consider genetics when designing nutritional programs to more precisely reflect an animals true nutritional needs. Existing models of nutrient availability and absorption are fitted to large data sets that reflect the average cow. Thus they will not precisely reflect nutritional needs of individual animals when they deviate genetically from the average animal. The use of genomics in the industry will offer opportunities to take advantage of the interaction between genetics and the environment where the latter includes nutrition, management, facilities, and climate. 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 a variety of knowledge gaps over the last 30 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, and re-invigorated in 2007; 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. For a few examples, work done in VA, MD and CA has resulted in an improved model of mammary function relevant to high producing cows; work in OH has leadled to better understanding of the role of rumen protozoa in digestive efficiency; work in WA and IL has used transcriptomic information in adipose and mammary tissue to identify key control points in efficiency; and work in MI, WA, WI, and OH has led to awarding of a large scale NIFA grant on dairy cattle efficiency.
Notably, in the last few years has added several new young scientists with modern molecular biology skills as well as an appreciation for and experience in integrative biology and bio-mathematics.
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. Although these objectives remain unchanged, we are definitely working at a more advanced and complex level than when we began. Research conducted by members of this group has been held in high regard by peers, attracted continued research funding, and perhaps most importantly, found continued application in the industry.
This committee continues its 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 controlling efficiency, 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 (this committee has sponsored 3 at FASS meetings in the last 7 years, and many of our members are routinely invited to regional, national and internationals conferences), 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.
The use of milk and dairy products continue to provide high quality food to the US population, provide employment for millions of people, economic viability to rural areas and maintains environmental sustainability by using a number of by-products of crops and food processing industries. More than 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 this 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. Major stakeholders include other scientists, practicing nutritionists, veterinarians, and farmers. Because feed inputs are a major determinant of milk yield, cow health, feed efficiency, profitability, and waste output, the work of the NC-1040 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. 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. Nutritional management is now far more than balancing and delivering high quality rations. We must account for and support not only milk production, but component production, reproduction, housing and productive life. Research and application in the traditional disciplines of genetics, reproduction, nutrition, health and management must be fully integrated to meet the needs of the dairy industry and society. The supply and demand of feed ingredients is leading to increased costs and volatility of availability and cost, and that is not likely to change. We need to have research and application that can rapidly and precisely respond to that volatility. Continued pressure to use resources wisely and protect the environment dictate an integrated approach, including the use of mechanistic bio-mathematical models that accurately describe genotype, phenotype and metabolism and production of cows.
Technical feasibility. This committee continues our long-term goal of making significant impacts in 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 in the context of our increasing complex knowledge and second they enable practical improvements in dairy cow feeding. Critical research needs are determined by using existing data from committee members and others 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 liver the adipose tissue; integration of the latest genomic knowledge, and alterations in milk 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. The recent changes in funding mechanisms requiring integrated multi-station projects is a clear indication of the validity of this approach. 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. Members of this committee continue to receive 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 has been profound in the areas of starch and protein chemistry and nutrition, feed processing, nutrient metabolism, lactation biology, metabolic control, systems biology and modeling. We have sponsored symposia at the FASS meetings in 2005, 2008 and 2011, and members routinely provide invited talks at this meeting in other sessions. 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.
Related, Current and Previous Work
Since the initiation of the last project in 2007, research in dairy cattle nutrition has moved forward on two major fronts: 1) evaluation of a growing number of co-products, primarily from the fermentation extraction industries and practical balancing and feeding of diets which replace grains and protein supplements of increasing cost with less costly forages or co-products; and 2) integration of genetics and nutrition to (finally) obtain quantitative information.
Meta-analysis technique was used to assess the effects of dietary sugar on DMI and milk production and composition responses in lactating dairy cows. Supplemental sugar tended to increase DMI by 0.38 kg/d, with a 95% likelihood that the true mean response lies somewhere between a decrease of 0.04 kg/d and an increase of 0.80 kg/d. Despite the finding that DMI tends to increase with sugar supplementation, there was no evidence that dietary sugar increased milk production, protein content, or ECM production. However, the meta-analysis did identify a tendency for supplemental sugar to increase milk fat content by 0.085 percentage units. This finding is consistent with recent reports suggesting that sugar can help to mitigate milk fat depression (Bradford and Mullins, 2012; Titgemeyer et al. 2011).
Use of alternative feedstuffs continues to be a major priority for the dairy industry. Perhaps lactating dairy cows fed 35% brown midrib (BMR) corn silage and 25% alfalfa hay (DM basis) would consume more DM around peak lactation compared to those fed convention corn silage (CS), resulting in longer peak milk production. DM intake was not different between dietary treatments, Cows fed the BMR diet tended to lose less body weight through peak lactation compared with those fed the CCS diet. While milk yield was not different between dietary treatments through peak lactation, milk yield post peak lactation increased by feeding the BMR diet compared with the CCS diet. Milk protein concentration was similar between dietary treatments (Holt et al 2012). Another experiment was conducted to determine the effects of corn silage (CS) hybrids and quality of alfalfa hay (AH) in high forage dairy diets on N metabolism and ruminal fermentation by early lactating dairy cows. While feeding BMRCS-based diets decreased urinary N output , it did not affect fecal N output. Feeding high quality AH decreased urinary N output , but increased fecal N output. Nitrogen efficiency (milk N /intake N )) was similar across treatments. Significantly decreased MUN by feeding BMRCS or high quality AH suggests improved whole-body N utilization efficiency.
Part of ruminal efficiency is in the activity of protozoal species. Isotrichid protozoa display chemotaxis toward glucose and peptides. By manipulating these species, we may be able to improve efficiency of digestion. Use of wortmannin to block phosphoinositede signaling was tested in continuous cultures. Isotrichids increased chemotaxis to glucose, but wortmannin decreased this response. Peptides were strongly chemorepellent to isotrichids, even in the presence of glucose and especially when preloaded with genistein or SNP. GTP had no effect on peptide repellence, although it reduced chemoattraction to glucose. For entodiniomorphids, U73122 increased random swimming into saline controls. Wortmannin decreased or did not affect swimming into saline but enhanced chemotaxis by entodiniomorphids to glucose. Wortmannins opposite results for entodiniomorphids versus isotrichids appear to be mediated through differences in vacuolization or receptor signaling mechanisms. For entodiniomorphids, motility toward chemoattractants appears to be sensitized by energy deprivation (wortmannin). Turning toward gradients is mediated through PKG; however, we could not support a direct PLC role (Firkins et al 2012, work in progress).
Feeding different co-products can result in different ruminal environments. Increasing particle length or decreasing fragility should increase the density of the rumen mat, rumination time, and the retention time of particles in the rumen in part by trapping smaller particles. There were no effects of a novel corn wet milling product on production of milk or milk components, but DMI tended to increase when 20% CMP was included with CS and with reciprocal effects on fat-corrected milk/DMI. Feed efficiency improved in AH diets compared to GH diets. For CS only, DMI decreased when CMP was increased from 20 to 30% CMP; in contrast, rumen DM pool increased. Grass hay increased total and liquid pool size of rumen contents compared with AH. Total time spent chewing increased in cows fed GH over cows fed AH by 35 min, partially due to a trend for increased minutes spent ruminating. Total tract digestibility of NDF, nitrogen, and organic matter were not affected by treatment. In situ digestion kinetics of NDF in CMP and forage and nitrogen in CMP were not affected by treatment. In diets containing low starch (with 4% corn grain), increasing CMP from 20 to 30% we need to consider interactions among forages on fill, digestion, and passage of fiber.
Expansion in the ethanol and biodiesel industry has led to an increased amount of by-products, such as glycerol, condensed distillers solubles (CDS), and dried distillers grains (DDG) available as potential alternative feeds. Diets containing either corn silage (no glycerol, 10% food-grade glycerol, or 10% biodiesel glycerol) or a CDS-stover (ensiled mix, fresh mix, and CaO treated) blend as the primary forage were fed, and CDS-stover blend diets replaced high moisture corn with biodiesel glycerol. Milk yield did not differ between treatments. Control and ensiled mix groups ate the most and cows on the CaO-blend ate the least. Also a difference in change of body weight was observed, where cows fed the CaO mix lost weight. Treated stover, biodiesel glycerol, and other biofuels products can be included in mid-lactation dairy cattle diets to partially replace corn silage and corn without an effect on milk yield or DMI (Donkin, 2012-NC-1040 report)
The cation-anion difference in dairy diets remains an important way to improve production and reduce disease. In a principal components analysis of earlier work with DCAD, both Na and K were positively associated with milk fat percent, FCM, and FE. However, Na was positively associated with DMI while K had no effect, suggesting a greater FE response to K supplementation. There was no effect of DCAD on DMI and milk production; DCAD had a significant linear effect on milk fat percentage and fat yield. Milk fat percentage was very low (2.58%) in the 250 DCAD group and increased up to 2.89% in the 400 DCAD treatment. Corresponding fat yield increased from 987 to 1,108 g/d. As expected the greatest response fat percent and yields came with the first two increments of DCAD (300 and 350) with a smaller increment in the 400 meq/kg DCAD treatment. Surprisingly, DCAD had a negative effect on milk protein concentration but no effect on protein yield. Diets needed to contain at least 406 meq/kg DCAD (K+Na-Cl equation; Erdman, 2012, NC1040 report)
Primarily under Objective 2
Work under Objective 2 hopes to improve our understanding of the metabolic mechanisms controlling efficiency. Major findings over the last 5 years include a better understanding of the regulation of gluconeogenesis in the liver (IN), adipose tissue gene transcription (WA, IL), gene transcription control in the mammary gland (VA, MD), regulation of milk fat synthesis (MD, NY) and in patterns of metabolism in the most efficient cows (WA). Work at MI has determined changes in residual feed intake and body condition score related to efficiency and that has led to a new NIFA large grant to study genetics of feed efficiency. We have learned more about specific control of adipose tissue lipid synthesis and lipolysis and the genes that control it such as fibroblast growth factor 2 (NY, PA) and the peroxisome receptor controlled cascade for fat synthesis (WA, IL) and hormone sensitive lipase and adipose triacylglycerol lipase (WA, IL). This work will allow us to focus into the large scale genome project to identify specific genotypes and phenotypes that control efficiency. Some recent work details are provided below.
A retrospective analysis was conducted of two experiments that induced milk fat depression while milking cows at equal intervals, three times per day. There was a significant effect of treatment and milking for milk fat concentration and yield, but no interaction of milking time and treatment.There was a treatment, but no milking time or treatment by milking time interaction on milk fat yield. Milk fat percent was lower at the morning milking, and a daily rhythm of milk fat concentration and yield can be observed in cows milked three times a day. However, diet-induced milk fat depression decreases milk fat yield equally over the day.
The variation in milk composition within a milking was studied in high producing cows. A milk-sampling device was designed to allow collection of multiple samples during a milking without loss of vacuum or interruption of milk subsampling. The average milk yield of the previous 7 milkings was used to determine 5 equal weight sampling intervals. If milk yield exceed expected by >25% of the interval weight a sixth sample was collected. Milk was collected during consecutive morning and afternoon milkings for all cows and was replicated one week later. There was an effect of milking (AM vs. PM) on total milk yield and milk protein, lactose, and fat concentration. There also was an interaction of milking time (AM vs. PM) and milking fraction, and a quadratic effect of milking fraction on milk fat, protein and lactose concentration. Milk fat content increased quadratically over the course of milk let down in high producing dairy cows, while much smaller changes were observed in protein and lactose. This pattern is consistent with previous results in lower producing dairy cows and reflects the dynamic nature of milk fat secretion from the mammary gland.
Switching to adipose tissue, a novel hormone known as Fibroblast Growth Factor-21 (FGF21) was shown to regulate lipid mobilization in laboratory animals but nothing is known about its regulation and role in lactating dairy cattle. We developed polyclonal and monoclonal antibodies for a homologous bovine assay. We have raised 4 independent rabbit polyclonal antibodies against bovine FGF21. These antibodies have been evaluated in 2 independent fashions. First, all 4 recognized bovine FGF21 when diluted between 1:5000 and 1:20000 in a modified enzyme-linked immunoassay format setting where bovine FGF21 is captured with an anti human FGF21 monoclonal antibody. These antibodies adequately recognize bovine FGF21. We have obtained over 1 gram of recombinantly produced bovine FGF21 to allow infusion in early lactating dairy cows. After refolding and purification, we have analyzed the protein on polyacrylamide-sodium dodecyl sulfate gels and established that it is over 99% pure. Finally, we have documented that it has a minimum level of endotoxins and that it is biologically active in two different bioassays (ability to stimulate glucose uptake and ability to stimulate ERK signaling in adipocytes). This material is therefore ready and suitable for infusion in dairy cows (PA).
Primarily under Objective 3
Under this project, we have been assembling a database to assess feed efficiency in lactating cows. To date, about 1600 Holstein cows from the US (WI and ISU are main contributors, along with MSU cows, as well as some from VT and FL) and another 3000 from Europe (Scotland and Netherlands) are included. The following data is based on 840 cows at UW, ISU, and MSU. On average, as cows eat more as a multiple of maintenance (MM) and produce more milk, feed energy is captured more efficiently. However, the marginal increase in efficiency is expected to decrease with increasing MM, especially with the decrease in digestibility predicted by NRC. The current data support this diminishing return and suggest a digestibility discount that is intermediate as illustrated. We suggest that once cows are above 3X maintenance on a lifetime basis, further increases in MM from more milk or smaller BW will return little gain in gross efficiency. Our best estimate at predicting DMI accounted for 77% of the variation in observed DMI across this dataset. Considerable variation in RFI exists for use in selection if it is heritable. Metabolic BW is assumed to be linearly related to maintenance requirement. Metabolic BW, BCS, and their interaction influenced NE captured. Efficiency decreased for fat cows, but not thin cows, as mBW increased. NE captured was not correlated with BCS and BW (R2<0.02). Across all BCS, heavier cows, especially those with mBW >140 (750 kg BW), were less efficient; this is reflected in greater RFI if mBW is not included in the RFI calculation. The increase in RFI matches the increase in DMI expected with increased mBW in NRC predictions. Including mBW in the RFI calculation removes any benefit to smaller BW, and therefore a penalty of 0.1 kg feed DM /mBW for mBW >140 (750 kg BW) should be considered. Accurate information on BW change may not be needed for identifying efficient cows.
Specifically within the rumen, fermentation in the rumen is a complex process involving microbial activities and degradable dietary components. The objectives were to evaluate extant volatile fatty acid (VFA) stoichiometric models for their capacity to predict VFA molar proportion and CH4 using independent data sources. Two data sets were organized from published literature. The first contained 141 treatments of rumen digestion studies with lactating dairy cows collected from 43 published experiments. The second data set contained 18 treatments from 8 studies. Model comparison was based on mean square prediction error (MSPE), concordance correlation coefficient and regression analysis. In general, models showed different prediction performance with respect to the type of VFA in rumen fluid with root MSPE (RMSPE, % observed mean) values from 5.2 to 43.2. Among the 4 models evaluated, that of Murphy et al. (1982, MUR) had the highest RMSPE value for propionate (25.7%) with 19.6% MSPE being random error. The model of Bannink et al. (2006, BAN) had the lowest RMSPE (10.7%) for butyrate with 97.8% MSPE being random error. Similarly, the model of Nozière et al. (2010, NOZ) had the lowest RMSPE (5.2%) for acetate with 83.0% MSPE being random error. The variation among stoichiometric models in predicting VFA production will have a major influence on the accuracy of estimated enteric CH4 production. There may be a need for more mechanistic approaches that consider nutritional and microbial factors rather than empirical models that relate VFA molar proportions to nutritional factors.
Specifically, within the mammary gland 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. Recent advances include update of the Molly model digestive and hormonal parameters (Hanigan et al., 2009; 2010). The newer models do a better job of predicting VFA and methane responses to dietary change (Hanigan et al., 2012; Gregorini et al 2013). A model of ruminal volatile fatty acid absorption and rumen epithelial blood flow was constructed to better describe observed effects of ruminal volatile fatty acid concentration and ammonia on absorption rates (Storm et al., 2012).
Model efforts have also looked at more traditional systems to improve our ration balancing models. Current energy evaluation systems for lactating dairy cows utilize key parameters such as the net and metabolizable energy (ME) at maintenance (NEM, MEM, respectively), efficiency of utilization of ME intake for milk production (kl), growth (kg), and efficiency of utilization of body stores for milk production (kt). A database containing energy balance observations on 600 individual dairy cows was assembled from 35 calorimetry studies conducted in the UK. A meta-analytical approach based on Bayesian methods was used to analyze the data as the conclusion reached is valid across studies. The data contained information on cows fed a wide range of forage proportions from 0.31 to 1.00. The primary covariates considered in the analysis were ME intake, tissue energy gain, tissue energy loss and forage to concentrate ratio (F:C as a continuous variable). The model was developed in the general purpose software for Bayesian modeling: OpenBugs. There was a significant effect of forage proportion on parameters for NEM. However, kg and kt were not significantly different in cows fed various proportions of forage. Net energy for maintenance was estimated to be 0.25 MJ/(kg0.75 d) (SD=0.024), where SD is the standard deviation. The results agreed with Strathe et al. (2011) who reported that kl was linearly related to metabolizability (i.e. ME/gross energy) of the diet, and predicted a 0.012 change in efficiency per 0.1 unit change in metabolizability. However, the magnitude of change in kl was higher when the analysis was conducted based on forage proportion compared to metabolizability. This may be because the calculated metabolizability had a narrow range in the dataset (0.42 and 0.76) compared to a wider range in forage proportions because of the nature of diet formulation to meet energy requirements.
The representation of mammary cells and cell activity in Molly was updated to better represent the loss of cells as lactation progresses and the shuttling of cells from active to quiescent pools in response to metabolite supply, hormonal state, and milking frequency (Hanigan et al., 2007). Work was also completed to assess the sensitivity of milk yield predictions by Molly, Cornell Net Carbohydrate and Protein System and the NRC model to changes in nutrient inputs (Bateman et al., 2008; Johnson et al., 2007) , and more recently to statistically derive ruminal and post-ruminal digestion coefficients including interactions among nutrients (Hanigan et al., 2012a) and to update the representation of hormones and gestational metabolism (Hanigan et al., 2009b) in Molly. Work was also completed to update the representation of N cycling across the rumen wall and improve the representation of N excretion in urine (Arriola Apelo et al., 2011) . Having assessed the validity of the representation of ruminal digestion, the focus of recent work has shifted to evaluating and improving the representation of volatile fatty acid production so that predictions of methane production can be improved (Hanigan et al., 2012b).
In the liver, glucose-6-phosphatase (G6Pase) is a rate-limiting enzyme in gluconeogenesis and catalyzes the release of glucose from liver. We determined the effects of cyclic AMP (cAMP) and dexamethasone (Dex) on G6Pase promoter activity. Basal luciferase activities of G6Pase promoter constructs were not different from pGL3-Basic, but were induced with exposure to cAMP as well as the combined cAMP and Dex. Dex alone had no effect on promoter activity. The responsiveness of G6P promoter to cAMP was decreased as the 5 end was truncated. The induction of promoter activity by cAMP or cAMP and Dex was eliminated by mutations of CRE2 in the proximal promoter . The data demonstrate a synergistic role of cAMP and Dex in regulating bovine G6Pase expression through promoter activation. Furthermore, the data indicate the sequence TTACGTAA located from -161 to -154 bp upstream of the TSS is essential for the induction of G6Pase promoter activity by cAMP or the combination of cAMP and Dex.
There has been significant new work on the changes in gene transcription during lactation and differences among animals of different genetic background and diet. Genes which regulate gluconeogenesis are expressed at higher amounts in early lactation animals, and are different among cows of different milk production (Hazelton et al. 2008; White et al. 2011). In continued work with the objective of identifying the patterns of metabolic flux in the most efficient dairy cattle, an existing mechanistic metabolic model (Molly, UC Davis) was used, a model that explicitly includes elements of genetic pedigree, including not only milk component production but metabolic interactions in the viscera and body. Efficiency of milk synthesis varied in a narrow range (81 to 84 %), while visceral energy use averaged 37 % of intake energy (range 33 to 46 %) and 68 % of maintenance (range 63 to 73 %). The variation in maintenance energy accounted for 37.6 % of the variation in milk energy efficiency (milk energy/absorbed energy). Expression of several genes coding for metabolic enzymes in adipose tissue were also related to efficiency of milk production. The model identified visceral energy and body energy (muscle protein turnover) as the two major contributors to variation in milk production efficiency. The amount of gene transcripts that control lipolysis including the ADRB2 and LIPE, accounted for 10 to 15 % of variation in efficiency. Transcripts of genes controlling lipogenesis, including SREBP, TSHSP14, LPL, and ACACA accounted for 15 to 18 % of the variation in efficiency. These results confirm some key metabolic control points that can be targeted for further research to define the genotypic and phenotypic control of metabolic efficiency in dairy animals (Sumner and McNamara, 2007; Kahn et al. 2013; Rocco et al 2013)
In related work, the selection herd at MN was used to determine differences in the serum metabolome between genetic lines. Effects of selection for milk yield on serum metabolome were assessed by comparing metabolite profiles of the University of Minnesota unselected (stable milk yield since 1964) control (CL) and contemporary, select (SL) lines of Holsteins. Milk yield per lactation between these CL and SL cows exceeded 4,500 kg. Serum samples from 5 CL and 6 SL cows collected at -14, -7, 3, 14, 28 and 38 DIM were separated by ultra-performance liquid chromatography and ionized chemical components detected by a time-of-flight mass spectrometer. Mass, retention time, and intensity of serum ions was extracted from chromatograms and spectra and used to construct a multivariate model by principal components analysis. Chemical structures of serum ions were determined by accurate mass measurement and MS/MS fragmentation. Differences in lipid species between genotype were detected and expression of genes involved in the metabolism of these lipids is being evaluated.
At the whole farm level, work was completed to assess the rates of ammonia loss from the barn floor (Hollmann et al., 2008), the economics and improvements in efficiency associated with reducing dietary protein (Stewart et al., 2012), and the potential influence of cow variance in milk urea N on protein feeding decisions at the farm level and the relation to ammonia emission (Aguilar et al., 2012; Burgos et al., 2010; Burgos et al., 2007; Johnson and Baldwin, 2008).
In the last 5 years, we have determined more specific information on feed analysis that allows nutritionist to balance rations using a variety of feedstuffs more effectively. There has been increased understanding of the phenotypic control of efficiency and we have made great improvement in the core metabolic model, Molly to improve its precision and use as the primary systems biology model in the dairy cow.
To quantify supply, availability, and interaction of nutrients and bioactive compounds utilized for efficient milk production while reducing environmental impact.
To identify and quantify molecular, cellular, and organismal signals that regulate partitioning and efficient conversion of nutrients to milk.
To use this knowledge of feed properties and metabolic and molecular quantitative relationships to challenge and refine nutrient requirement models leading to more precise feeding systems for dairy cattle.
MethodsThe work plan will be organized around the 3 objectives: 1) To quantify supply, availability, and interaction of nutrients and bioactive compounds utilized for efficient milk production while reducing environmental impact; 2) To identify and quantify molecular, cellular, and organismal signals that regulate partitioning and efficient conversion of nutrients to milk and 3) To integrate nutrient flow, regulation, and genomic information using a systems approach to improve dairy herd efficiency and sustainability. 1) To quantify supply, availability, and interaction of nutrients and bioactive compounds utilized for efficient milk production while reducing environmental impact.
Work will define the value of biofuels crop residues for lactating dairy cattle, including the upper limit in the ration to maintain efficiency. At SD, work will identify and evaluate methods to improve feed efficiency through traditional and new forage hybrids. Higher forage diets will be studied at SD for the maximum effective use in dairy cows diets to help offset the rising costs of grain. Work will include testing of new forage hybrids that can be used more efficiently. Methods will include not only feeding, but in vitro continuous culture systems in order to more rapidly test possible use. Work will also include determination of the feeding value of new forage hybrids.
At UT, work complementary to that at SD will focus on developing optimal forage feeding programs with focus on corn silage (CS) and alfalfa hay (AH) on dairy diets. Combined in vitro and in vivo research experiments will provide optimal feeding program to maximize use of CS and AH in dairy rations to significantly improve feed efficiency. Also, the impact of alternative feeds and additives such as feed enzymes, direct fed microbials, oils, and oilseeds on ruminal fermentation characteristics and animal performance will be evaluated. An efficient combination of in vitro and in vivo experiments will be carried out to identify viable ruminal fermentation modifiers. At IA, work on probiotics in dairy diets to improve feed efficiency will complement the work at UT and SD. At PA, members will study to refine our use of higher fat diets to partially replace energy lost from grains. Care must be taken as to the form, fatty acid profile and unsaturation level. Work will determine safe types and amounts of fats to maintain efficiency without negative effects on milk fat synthesis. This will be coordinated with studies at WI which aim to study the effects of low linoleic acids fats in order to get the benefits of fat without negatively affecting milk fat composition or the partitioning of nutrients to milk.
Coordinated with these efforts above to utilize lower grain diets and potential additives to improve performance, work at MN will evaluate effects of dried bacterial cells on amino acid flow and microbial fermentation, using dual flow continuous culture fermenters, in order to determine if we can improve efficiency of ruminal efficiency. At MN, members will study the effectiveness of bismuth subsalicylate (BSS) on microbial fermentation and gas production. The role of protein nutrition in practical diets and efficient support of milk production will be studied at PA. Members will further investigate the possibility of maintaining high milk production and milk composition in dairy cows fed metabolizable protein (MP)-deficient diets. They will investigate specific amino acids which may limit milk production in these diets; determine the relative role of digestible Lys, Met, and His for maintaining milk and milk protein yields in cows fed MP-deficient diets, in which ruminally-degradable protein (RDP) is not limiting. Work will also determine the role of ruminal microbial protein composition on amino acids supply and limiting amino acids in MP-deficient diets and determine the relative roles of RDP vs. individual amino acids deficiencies as regulators of feed intake and milk production in dairy cows fed MP-deficient diets. This work is critical for this project as not only are grain sources under tremendous demand and price increases, but so are protein supplements. In related work, WA will study the effect of using a fermented whey product (Lactowhey, Packerland Whey Products) for replacing higher cost protein supplements such as soybean meal and canola meal. Mechanisms of rumen microbial stimulation by this product will be determined.
This project does not only focus on lactating dairy cattle, but in improving calf and heifer growth to supply efficient dairy cattle. At PROVIMI, work will focus on improving digestibility of diets for calves, refining the amino acid needs and fatty acid requirements of neonatal calves, especially focusing on improving immune function.
Work under Objective one directly contributes to work on Objectives 2 and 3, to connect the practical dietary management of the cow with the underlying metabolism and then integrating all of this into models for research and application. Work at CA will help integrate the work done under Objective 1 by quantifying variability in nutrients supplied through on-farm feeding management systems and measuring the variability in cows response through milk production and milk components, blood nutrient supply, and rumen pH. This work will help integrate the practical effects of feed variation with the genetic and phenotypic variation among cows to make better practical decisions on farm and for research.
2) To identify and quantify molecular, cellular, and organismal signals that regulate partitioning and efficient conversion of nutrients to milk Work under Objective 2 aims to help explain the practical effects of dietary composition and feeding management work under Objective one by exploring the digestive, physiological and metabolic mechanisms of response to diet, as well as to explore the mechanistic reasons for variability among animals. Integrating research from the practical to basic levels has always provided a highly efficient research model for faster improvement in understanding and application. This project has always had a strong basic research component, and many members are funded by competitive grants to explore the underlying mechanisms which dictate dairy cattle efficiency.
One such success story has been the work headed at MI which was awarded a NIFA grant on genetics of feed efficiency. Several members of this group (WI, KS, VT) are formal collaborators and almost all members are informal collaborators. The work plan under this project is to 1) Develop a large database of cow inputs and outputs; 2) Determine the heritability of feed efficiency; 3) Characterize the genomic architecture of feed efficiency and related traits and develop genomic selection techniques for feed efficiency; 4) Determine if feed efficiency is repeatable across diets varying in fiber and protein concentrations; 5) Determine if there is an optimal level of milk production for efficient production of milk and 6) Examine existing models for feed energy supply and determine if changes are needed. Clearly this work is an umbrella project linking all aspects of dairy cattle feed efficiency, over all three objectives of this NC project. This work promises to make great leaps in our understanding and practical application of feed efficiency management in dairy cattle by 2018.
To help meet Objective 2, members at OH and VT will assess the effects of nutrient supply and the thermodynamic effects of volatile fatty acid (VFA) and hydrogen concentrations on VFA production rates, interconversions among VFA, and net hydrogen production in a continuous fermenter system. These observations will be extended to the in vivo state using stable isotope infusions to assess de novo VFA production rates and interconversions among VFA using 3 or 4 of the treatments tested in vitro. The resulting production and interconversion data will be used with literature data to improve existing models of VFA production (Obj. 3).
In addition, the effects of individual essential AA (EAA) on milk protein synthesis rates and post absorptive efficiency will be determined in a protein limiting environment. Stable isotope infusions will be used to assess post absorptive efficiency. Treatments will include a positive high protein and negative low protein control plus each of 3 EAA provided individually and in combination. The 3 EAA used will be determined based on tissue slice work which has already been completed. If positive milk protein responses are observed, mammary biopsies will be taken to assess the relationship between milk protein synthesis and cell signaling state.
Related to the broad objectives under the large grant managed at MI, members at WA will use an existing data set of mRNA transcription arrays in liver (n = 24) and adipose tissue (n = 72) of cattle in late pregnancy and early lactation to determine the key phenotypic differences among cows of varying feed efficiency. Using a data set on more than 60 cows built up under the auspices of this NC project since 1987, WA will integrate the gene transcripts, adipose tissue metabolism and practical on-farm efficiency measures to determine the patterns of metabolism in the most efficient cows. This data set will be used under Objective three to build more sophisticated models asking specific questions about metabolic efficiency.
In related work, members at Cornell (NY) have shown that plasma FGF21 is abruptly increased in early lactation. These data were obtained using an assay with limited availability. Accordingly, the team will complete its effort to develop a bovine specific assay to measure plasma and tissue FGF21. This assay will be used to identify the primary factors regulating FGF21 production in lactation, such as other metabolic hormones (e.g., glucagon, growth hormone, etc), supplemental dietary lipids, and metabolic fuels such as nonesterified fatty acid. They will determine the regulatory elements for critical metabolic processes in liver that support milk production and cow health including gluconeogenesis, ketogenesis and amino acid metabolism. Liver and adipose tissue are primary FGF21 target tissues in dairy cattle, but specific FGF21 effects in each tissue remain unknown. Accordingly, the Cornell team will study the effects of FGF21 on bovine cell culture systems, starting with pre-adipocytes and mature adipocytes. The focus of these studies will included intracellular FGF21 signaling and effects on metabolic endpoints of interest in the context of lactation such as expression of genes encoding lipogenic and lipolytic enzymes, rates of lipogenesis and lipolysis. This work will specifically dovetail with that ongoing at WA.
At PA, related experiments will be conducted to investigate the mechanism of bioactive fatty acids in adipose and mammary tissue. The results will provide insight into the functionally important lipogenic regulatory mechanism in the cow and identify candidate systems to improve the efficiency of milk fat synthesis. This work will be coordinated with that at NY and WA to identify the key controllers regulating lipid synthesis and overall efficiency. At CA, work will help determine the relationship between mitochondrial efficiency and feed efficiency for cows in different stages in lactation and different diets as a tool to select for more energy efficiency cows.
Thus, work under Objective 2 will provide a very detailed understanding of the genotypic and phenotypic control of efficiency in high producing dairy cattle. This body of knowledge will be essential in improving our research and practical application models under Objective 3.
Objective 3: To integrate nutrient flow, regulation, and genomic information using a systems approach to improve dairy herd efficiency and sustainability. The core of this project is to integrate research and practical application in a specific systems approach at multiple levels of biological organization, from the subcellular to the herd level. This project has a rich history of integrative research, long pre-dating the new (and welcome) focus at NIFA on systems research. Our goal is to construct and refine integrative research and practical models that can be used in focused research programs connecting genetic, physiological and metabolic control of efficiency.
To that end, work under this objective will integrate new knowledge and data from the research experiments of project members and the rest of the scientific community using statistical and mechanistic modeling approaches to better define nutrient digestion and metabolism, animal performance, and excretion and emissions from dairy cattle. Major improvements in the descriptions of nutrient digestion; energy use for maintenance functions; metabolism of amino acids, and hormonal regulation of metabolism have been made during the present project activity (2007-2012). Further improvements will continue to center around these critical areas, and expand to include a better representation of volatile fatty acid production and metabolism and the generation of methane. Stations including CA, WA, MI, WI and VA will collaborate on this model expansion and also investigate other modeling techniques that will provide information for the development of Molly and evaluation of other precision feeding systems. The digestive and performance database used by the NRC 2001 committee has been expanded to include trials from the last 10 years and will be used along with feed efficiency observations from 8000 cows to be enrolled in the MI led genomic feed efficiency effort to further evaluate the 2001 NRC and Molly cow models (VA). These evaluations will be used to guide further model development work. VA , MD, and OH will collaborate to assess the impact of thermodynamic control on volatile fatty acid production. This will be achieved by introducing thermodynamic elements into the Molly cow model, updating the representation of volatile fatty acid absorption to reflect new knowledge, rederiving the coefficients relating de novo volatile fatty acid production rates to fermented nutrients, and comparing predictions from the revised model to the former model to determine if accuracy and precision are improved. VA will complete the integration of cell signaling components into an existing mammary tissue model and test that model against all available literature data to assess the relative impact of amino acid regulation of milk protein synthesis. Should the approach prove valuable, an aggregated representation of it will be introduced into the Molly cow model and a further round of evaluation against literature feed efficiency data will be undertaken. VA will also collaborate with Guelph to refine, evaluate, and aggregate an existing representation of post-absorptive amino acid metabolism for use in ration balancing systems including the NRC 2001 model. This model will address the problem associated with the assumption of fixed post-absorption protein efficiency by introducing a variable efficiency concept, and it will more accurately represent use of essential amino acids for maintenance and productive functions.
It is also our intention to begin a construction of a map of dairy cattle metabolism including at the gene expression, proteome and metabolomic levels. This will be achieved by development of lower level models to integrate the high density data. These models will provide functional descriptions of the transcriptome, the proteome, and the metabolome. Once validated, these models will then be used to derive aggregated representations of the interaction of nutrients with genes and gene products. Key equations derived from this work will be integrated into the Molly model to test the impact of consideration of such elements on predictive performance and to provide quantitative integration of that knowledge with the historical knowledge captured in that simulation program. Although initial efforts in this area will be clearly for research purposes, long term application goals would include, for example, identifying the patterns of gene expression leading to the most efficient use of nutrients; or to identify specific dams and sires with desirable gene expression patterns to use in an advanced selection strategy. The present work on mapping the control of expression of gluconeogenic control enzymes in liver (IN, WA), modeling the cell signaling pathways controlling milk protein synthesis (VT), and gene expression analysis of lipogenic and lipolytic control enzymes in adipose tissue (WA, MI) are examples of the beginning of this long term process.
Researchers at California will collaborate with VA, WA and PROVIMI (Provimi is a private company, formerly AKEY, from which Dr. Gale Bateman is collaborating with the committee) in Molly model development and better partitioning of maintenance using new ATP yields. New maintenance estimates along with the newer ATP yields should provide better models relative to energy utilization. The revised model will be evaluated using a broad range of literature data and the USDA Beltsville chamber data to determine accuracy and precision of nutrient partitioning. The Molly model and manure emissions models will also be evaluated using literature and USDA data from experiments using varying dietary N levels and N flux chamber work from CA to determine the accuracy and precision of urinary and fecal N excretion and ammonia emission predictions. Workers at CA, WA, VA and PROVIMI will continue to work on modeling structures to improve optimization of metabolic and nutrient requirement models. This is important because it will allow faster and more thorough testing of the effects of feeding practices, nutrient content of the feed and genetic efficiency. This will speed the outreach efforts to get research results, validated by thorough analyses, out to the industry clientele. Workers at WA, CA and VA will continue, update and expand several efforts to improve the model, integration of information, and outreach to the industry. The goal is to expand the past efforts of this group into a useful scientific description of the interactions of nutrient absorption, gene transcription and ultimate efficiency of dairy cows and improved precision of feeding them.
Some specific efforts under this objective include work at VA in which the Molly cow model will be modified to include consideration of thermodynamic effects on VFA interconversions, and the VFA stoichiometric coefficients rederived by fitting to a large set of VFA concentration data and a smaller set of VFA production (in vivo and in vitro) and interconversion data including those data collected in Obj. 2. Parameters defining VFA absorption will be rederived to remove existing bias and bring VFA production and concentration predictions in line thus allowing VFA production information to be derived from the concentration data.
We will use previously collected cell signaling and casein synthesis data to complete and parameterize a mammary tissue model. The revised model will be compared to the base model using a large set of mammary arteriovenous difference data from the literature. Key concepts from that model will be leveraged to improve the representation of the regulation of milk protein synthesis in the Molly cow model, and the model will be tested with a large literature data set. Finally, a set of EAA requirement equations will be derived in collaboration with Guelph based on the concepts of independent and additive responses to individual EAA as observed in our work. These equations will be constructed for use in ration balancer equations and will be tested against a large observed dataset constructed from literature observations.
Work coordinated between VA, MI and WI will to evaluate the 2001 Dairy NRC using a large dataset of literature observations and individual cow data collected on a feed efficiency project to identify limitations in the model. Alternative representations of prediction equations put forth by committee members will be incorporated into the model and tested for validity and improvements in accuracy. Similar evaluations of the Molly cow model will be conducted using the same data sets to identify deficiencies and subsequently to test hypothesis.
At PROVIMI, members will design and implement an on farm nutrition model for growing calf and heifer (empirical model); and will continue to refine a proprietary nutrition model for feeding dairy cows, including describing greenhouse gases, digestibility depression with increasing intake, feed descriptions and impact of additives on nutrient flow. This work has the goal to design and implement on farm tools to assist in monitoring feeding management to reduce environmental impact.
At CA, specifics will include extending the development and solution of a linear programming model including more variability in pricing and other input which will allow more realistic examination of changes in CH4 emissions and mineral excretion in dairy cattle and which will be able to jointly optimize reductions in CH4 emissions (or any GHG) with diet costs; to evaluate in intro models for fermentation using a simulation approach to determine the limitations of the most widely used models; to investigate analyzing energy partitioning using a multivariate approach using metabolizable energy intake, milk energy and tissue energy and to develop new methane prediction equations using key variables for prediction and estimate variance components and uncertainty of methane emissions from dairy cattle and compare these estimates with current models.
Measurement of Progress and Results
- Updated and validated model integrating the newest data on feed chemistry and physical factors into our nutritional models.
- Development and dissemination of specific guidelines on inclusion rates for co-products in dairy diets
- Development and dissemination of a next-generation research model of gene expression control of efficiency
Outcomes or Projected Impacts
- Continued improved natural resource use efficiency, including co-product use and higher forage diets.
- Improved environmental impact, better utilization of N and less N waste
- Improved use of decision support tools in ration balancing
- Publication of a metabolic gene map integrating transcriptome, metabolomic and practical dairy outputs
Projected ParticipationView Appendix E: Participation
The outreach plan continues to have two related goals: dissemination of novel research findings to a broader scientific audience, that encompasses many scientific disciplines; and dissemination of research findings of a more practical nature to audiences of producers, consultants, specialists and other allied industry leaders. This committee covers a broad range of dairy research, and as such has many stakeholder groups.
The outreach plan continues to have two related goals: dissemination of novel research findings to a broader scientific audience, that encompasses many scientific disciplines; and dissemination of research findings of a more practical nature to audiences of producers, consultants, specialists and other allied industry leaders. This committee covers a broad range of dairy research, and as such has many stakeholder groups.
For the first goal, our scientists conducting novel, fundamental basic research related to dairy cattle metabolism and nutrition all disseminate our research results at the American Dairy Science (FASS) meetings to other scientists and specialists. We also, as individuals, are invited to many national and international scientific conferences to present our research. Most committee members have given multiple talks at international symposium in energy and protein metabolism and in modeling. Many have given talks at Animal Nutrition Conferences across the US.
In part, our education and outreach success can be measured by continual invitations to present at scientific meetings; the group collectively has given several dozen invited talks at meetings for since 2007; published in highly regarded scientific journals in biochemistry, physiology and genomics (Am J Physiology; Physiological Genomics; System & Applied Microbiology), metabolism (Endocrinology; J. Interferon Cytokine Research), nutrition (Journal of Nutrition; Animal Nutrition) and dairy and animal science (J. Dairy Science, J. Dairy Research, J. Anim. Sci, Anim. Feed Sci. Tech.). We have had continued success in obtaining research funding from private and public institutes. Six members of this committee have earned extramural support just from the USDA/CSREES (now NIFA) National Research Initiative in Growth and Development (Project 42), a very competitive program. Several committee members (MI, WI, VT, IA) are funded by a NIFA large grant on genetics of feed efficiency.
For the extension goal (dissemination of research findings of a more practical nature to audiences of producers, consultants, specialists and other allied industry leaders); each one of the collaborators on this project works in a state with extension faculty (the list includes ALL collaborators), and several collaborators also have an extension appointment (PA, MI, WI). Information from this committee has been and will continue to 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. Every major animal nutrition conference (Cornell, Minnesota, California, Southwest, Pacific Northwest, Intermountain) routinely has committee members presenting information to consultants, nutritionists and industry people.
The members of this committee continually discuss with our producers and allied industries to move forward in effective and meaningful research and application programs. At the aforementioned national, regional and local conferences, we will meet in groups and individually with producers, veterinarians, nutritional consultants and private industry scientists to discuss research results and plans. Producers and nutritionists will receive up to the minute information on the latest in practical nutritional management, through the use of extension bulletins, local and regional producer meetings, regional and national conferences, trade publications and personal conversations and correspondence.
Although the outreach and extension program is an important part of the project, the primary activity of most collaborators is in basic and systems research. The stated outcome of this basic research however includes one specific objective to improve and expand the development, refinement and use of nutritional decision support systems, or models, such as the National Research Council Nutrient requirements of Dairy Cattle, the CPM Dairy model, or the research model, Molly. This is truly the ultimate goal, that our research lead to specific, definable bio-mathematical equations that apply to the nutrition, metabolism, and thus efficiency and production of dairy cattle. Five members (Hall, Hanigan, Hristov, McNamara and VandeHaar) are members of the new NRSP-9 National Animal Nutrition Program to help coordinate new research in models and publishing nutritional models.
We will measure impacts of our outreach, education and extension program, not only in numbers and dollars of extramural funds and numbers of papers published and talks given, but in continued improvement and use of nutritional decision support systems that integrate our research findings. Some examples include applied research into use of co-products, better balancing of forage and concentrate ingredients through use of the NRC and CPM Dairy models, and better information on feeding transition cows to reduce metabolic diseases. Basic research centers on genotypic and phenotypic control of efficiency. Findings from this group continue to save dairy producers money and increase overall efficiency of milk production.
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. 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. The committee has hadded 10 new or replacement members since the last revision.
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