NC2040: Metabolic Relationships in Supply of Nutrients for Lactating Cows
(Multistate Research Project)
NC2040: Metabolic Relationships in Supply of Nutrients for Lactating Cows
Duration: 10/01/2018 to 09/30/2023
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 as well as many states. Our long-term goal is to improve the efficiency of milk production, cow health and longevity, and thus promote environmental and economic sustainability in the US dairy industry. Our approach to achieve this goal is to systematically identify those biological and nutritional management processes that will provide the greatest improvement and to concentrate our research efforts there. This is done partly through the construction, challenge and evaluation of computer-assisted bio-mathematical models that describe the metabolic relationships between feed inputs and milk outputs of cattle. We have chosen the term precision feeding systems in this revision to reflect the goal of being able to feed dairy cows that widely differ in genetics, environment and diets, not to reflect any particular methodology or feed delivery system. Although dairy producers, large and small, feed in a large variety of ways, a major goal is to be precise in meeting the needs of their cows.
Improvement in animal and resource efficiency is slowed by a lack of clear research priorities addressing the most critical areas. This is due to a combination of factors, including: lack of quantitative data regarding absorbed nutrients and the metabolic responses of cows to those nutrients; a lack of integration of existing data into bio-mathematical models that will point out areas of greatest need; and a lack of real and enthusiastic support in the research and funding communities for cooperative, large-scale, integrated research work. In addition, integration of recent discoveries concerning genetic regulation, animal genotypes and phenotypes (genomics, gene arrays, proteomics, metabolomics), into traditional nutritional science in animal agriculture has been slow. Recent technological advancements and an appreciation for the importance of genotype in nutrient use by dairy nutritionists are now increasing the pace of that integration. This holds great promise for quantum improvements in efficiency (10 to 15 % on a herd basis as opposed to the traditional incremental increases).
Our committee has addressed these lacks in knowledge steadfastly in the last 35 years, including the last 5, and the research and outreach done by this group continues to improve the understanding and efficiency of dairy production. The committee is comprised of some of the preeminent dairy scientists in the US with a broad base of specialties that encompass feed analysis; feeding management; ruminal microbial metabolism; intestinal digestion; physiology and metabolism of major organ systems; molecular and cellular biology; mathematical modeling; and the role of nutrition in health and longevity of animals. In the revision beginning in 1987, a conscious effort was made to plan and conduct experiments to provide data to improve research and practical nutritional models. Research done since then has come a long way to do that, however much remains to be done. For reasons given in the previous paragraph, improvements in complex research design, conduct and interpretation, including integrating information into model systems, has been slow. Yet this committee has continued to do excellent scientific work in practical and basic dairy nutrition. New additions to the committee in the past 5 years have maintained our traditional strength in applied dairy nutrition while also enhancing expertise in rumen microbiology, molecular biology, and quantitative analysis. The committee is not dying off and wrapping up work, but rather changing and setting new goals, all under the umbrella of feeding and metabolism of dairy cattle.
We have retained our title and objectives as these are still closely reflect our collective mission. Our first specific objective is to quantify properties of feeds that determine the availability and utilization of nutrients critical to milk production. Our second specific objective is to quantify metabolic and molecular interactions that alter synthesis of milk components. Our final objective is to use this knowledge of feed properties and metabolic and molecular quantitative relationships to challenge and refine precision feeding systems for dairy cattle.
This committee has had a strong history in both basic biological research and practical application, and we intend to maintain that breadth. The overarching, ultimate goal is to do sound research directed toward finding out the most specific biological concepts and processes, and to apply that knowledge to the improvement of dairy cattle feeding in the practical work. Results from work done by this committee will be disseminated to practicing dairy nutritionists, veterinarians, extension specialists, farmers, and other scientists through regional nutrition conferences, trade and extension publications, electronic media, frequent national symposia, and applied computer ration balancing programs. Our work contributes to 1) improved accuracy of feeding standards for dairy cattle and future National Research Council publications on the nutrient requirements of dairy cattle, 2) standardization of analytical methods for feed evaluation, 3) reduced losses of nutrients to the environment from dairy cattle, 4) profitable and environmentally sustainable use of available feedstuffs, 5) continued expansion into new areas of genetics and nutrition and integrative biology and 6) continued supply of affordable, nutritious products for human consumption.
The need as indicated by stakeholders. Approximately 50% of the calcium, 20% of the protein, and 10% of the energy in the US diet are supplied by dairy products; thus, the US consumer is a major stakeholder for the NC-2040 committee. Consumers want dairy products that are safe and inexpensive, but increasingly they also want an environmentally friendly dairy industry that promotes animal well-being. Recently, attention has been given to bioactive molecules in milk (in addition to Calcium) such as conjugated linoleic acids. Yet at its core the NC 2040 committee functions to do basic and applied research on the feeding and nutritional biology of dairy cattle. Major stakeholders include other scientists, practicing nutritionists, veterinarians, and farmers. The needs of these stakeholders have been addressed by the Food Animal Integrated Research group in the FAIR 2002 document. The goals of FAIR 2002 are to strengthen global competitiveness, enhance human nutrition, protect animal health, improve food safety and public health, ensure environmental quality, and promote animal well-being. Because feed inputs are a major determinant of milk yield, cow health, feed efficiency, profitability, and waste output, the work of the NC-2040 committee is critical for most of these goals.
The importance of our work. Natural resources are used efficiently when milk production per unit feed and per cow is high (Baldwin, 1995; VandeHaar, 1998). To efficiently produce milk, a cow must have a well-developed mammary gland and be able to supply the gland with the nutrients it needs. Nutrition in the first year of life affects mammary gland development, and nutrition around the time of calving and throughout lactation has a major effect on the health, productivity, and efficiency of cows. Feeding for optimal nutrient intake requires not only the provision of the necessary nutrients for milk production but also consideration to the effects of diet on mammary capacity and on appetite, health, and metabolic regulation of the cow. Because feed costs account for half of all costs on a dairy farm, nutrition also significantly impacts farm expenses. The NC-2040 committee considers all of these factors for optimal feeding. For example, if we could maintain current milk production while feeding diets with 4 percentage units less total protein, we would decrease N losses to the environment in the US by 300,000 metric tons per year and save US dairy farmers $540 M per year in feed costs. [This calculation assumes 1) dry matter intake is 20 kg/d, 2) US cow population is 9.2 M, 3) efficiency of milk protein production (milk protein/protein intake) is 0.3, and 4) cost of crude protein is $0.20/kg.] This type of progress only can be made if we take an integrated approach, with the use of mechanistic bio-mathematical models that accurately describe metabolism and production of cows.
Technical feasibility. This committee has a record of making significant impacts in our knowledge of dairy cattle nutrition and metabolism and in the way that dairy cattle are fed and managed nationwide. We use the same approach that has proven effective in the past: that is to challenge and refine our models of dairy nutrition and metabolism. Computer-based, mechanistic, and quantitative metabolic models are useful in two ways: first, they help us determine critical needs in research and second they enable practical improvements in dairy cow feeding. Critical research needs are determined by using existing data from NC-2040 members or conducting new experiments to test model predictions of physiological responses to experimental diets. Examples of such responses include, rumen pH, microbial growth and function; alterations in gene expression and hormonal release of organs such as the adipose tissue; and alterations in milk fatty acid compositions. By challenging our working models in this way, we identify shortcomings that then become the basis for developing new testable hypotheses for further experimentation. Results from new experiments are incorporated into the models, and they are challenged again for further refinement. Thus, we continue to build our models so they are more mechanistic, quantitative, and accurate. These qualities enable us to improve practical feeding recommendations for dairy cattle in a variety of environmental and feeding conditions.
Need for Cooperative Work. Important and complex problems require coordinated effort of many personnel. Considerable progress has been made in dairy nutrition, but practical problems remain and no single research group has the skills and resources needed to solve them alone. Only through cooperation can State Experiment Stations address the complex interactions among feed supply, nutrient use, genetic capability, and milk composition. Our committee is comprised of dairy scientists with a broad base of specialties that encompass feed analysis, feeding management, ruminal microbial metabolism, intestinal digestion, physiology and metabolism of splanchnic, adipose, muscle, and mammary tissues, endocrine regulation, molecular and cellular biology, and mathematical modeling. Furthermore, in testing and refining nutrition models for the whole country, we must consider the variation in forages and environment that exist among regions. Thus, we have scientists from every dairy region in the country. In addition, the explosion of new information in genomics, gene expression, gene array work, metabolomics and proteomics requires that we integrate this knowledge into our understanding of metabolic efficiency. Cooperation among stations is required to deal with this information and to solve problems, and will have a national impact in understanding the complex interrelationships of nutrient digestion and metabolism in lactating dairy cows and to apply this knowledge.
Impacts on Science and Other Impacts. This project exemplifies the proven effectiveness of the cooperative regional approach. As detailed in the "Related Current and Previous Work" section below, results of this cooperative effort have become benchmarks of scientific progress and have led to practical feeding recommendations used worldwide. Project Leaders for the NC-2040 regional project have received numerous awards for research, both basic and practical, from the American Dairy Science Association, the American Society of Animal Sciences, and industry groups. Most of the Project Leaders are in continuous demand as speakers for scientific and industry conferences in nutrition. The impact on basic and practical nutrition from Project Leaders has been profound in the areas of starch and protein chemistry and nutrition, feed processing, nutrient metabolism, and lactation biology. This group provided a major contribution to the 2001 version of the National Research Council’s (NRC's) Nutrient Requirements of Dairy Cattle. Four of the 10 scientists on the NRC panel were from the NC-185 committee, and a significant portion of the data used in the latest edition came from NC-1009 committee members. In 2005, the group presented a symposium at ADSA/FASS on regulation of nutrient use in dairy cattle (references are in bibliography). Currently, a committee is revising the NRC Nutrient Requirements of Dairy Cattle, and 7 of the 13 members are current or former members of NC2040. Thus, this committee has had a major impact on improving the biological, economical, and environmental efficiency of the US dairy industry. We continue to recruit and support young scientists to keep the committee current and effective year to year.
Related, Current and Previous Work
Cattle can be extremely efficient producers of quality human food. A major goal in feeding cattle is to find the optimal combination of chemical and physical properties of feeds that provides the proper amount and balance of absorbed nutrients to match the genotype of the cow or herd. This is a challenge because of the tremendous variety of feedstuffs available, the complexity of interactions among feed particles, nutrients and organisms in the rumen, genetic variance within and among herds, and the rapidly changing nutrient requirements of a cow around the time of parturition. The amount and profile of absorbed nutrients in dairy cattle are a function of rumen fermentation and intestinal digestion. What follows is a brief summary of advancements since the last revision in 2013 and plans for continued work.
Primarily under Objective 1
Over the past 5 years, research under Objective 1 has returned to an emphasis on understanding nutrient/microbe/gut interactions that affect dairy cow nutrition and health. Although this has been of interest dating to the earliest work of this committee, new discoveries and tools from our colleagues in the biomedical world have re-energized efforts in this space. A second area of emphasis is the evaluation of novel feed products (including specialty fats and bypass amino acids) to provide unbiased information on how they impact cows. Finally, impacts of animal genetics and diet on feed intake are being explored.
Understanding constraints to microbial efficiency (OH and FL stations)
With batch culture experiments, work by committee members showed that microbes direct ATP energy away from growth and towards energy sinks, such as glycogen synthesis and energy spilling. It showed that glycogen synthesis was an especially important sink for protozoa when dosed with moderate excesses of carbohydrate. Other work from these stations suggested that genomes of rumen bacteria encode ion pumps and other enzymes that should increase ATP generated from carbohydrate fermentation. Some models predict production of microbial protein using ATP yield from fermentation, and these models may need to be revised.
Further optimization of the efficiency of microbial protein synthesis (EMPS) to more efficiently convert dietary nutrients into milk components requires a better understanding of microbial metabolism. The branched-chain amino acids (BCAA) are rapidly decarboxylated from their respective volatile fatty acids (BCVFA) by bacteria (probably through an enzyme complex linked to electron-transport phosphorylation to generate ATP). As shown in pure cultures, BCAA can be limiting for fibrolytic bacteria that lack expression of a critical enzyme needed in de novo BCAA synthesis (from glucose). For those bacteria, reductive carboxylation of BCVFA to BCAA is important for growth and therefore to maintain ruminal fiber digestibility. The BCVFA (particularly 2-methyl butyrate) increase fluidity of bacterial membranes as needed during varying dietary conditions. With the discovery of up to 1/3 of ATP production/glucose from electron transport phosphorylation (Hackmann and Firkins, 2015), differences in bacterial membrane integrity resulting from feeding unsaturated fat should explain variation in EMPS. The role of supplemental fat on EMPS has been suggested to be a result of inhibition of protozoa and sparing energy (really the carbon that could make ATP via fermentation) by microbial uptake of fatty acids, but neither role has been well documented. A recent meta-analysis (Roman-Garcia et al., 2016) revealed that valerate (coeluting with 2-methyl butyrate) or isobutyrate interacted with ammonia, so BCVFA appear to be limiting ruminal EMPS in high producing cattle under certain dietary conditions. OH researchers therefore are studying the role of BCVFA concentrations under different dietary conditions, including supplementing unsaturated fatty acids, to enhance EMPS.
Influencing ruminal metabolism (PA and VA stations)
PA investigated the effect of diet on induction of milk fat depression including the effect of monensin on recovery from milk fat depression, ability of a methionine analog to inhibit milk fat depression, and the alterations of rumen microbial populations during diet-induced milk fat depression (Rico et al., 2015a,b). Research in VA is being conducted to assess the effects of varying dietary fiber, starch, protein, and fat on de novo VFA production in the rumen and interchange among VFA. These flux measurements are being linked to mRNA expression patterns and microbiome composition. The overarching goal of the work is to synthesize a matrix of observations that can be used to test existing models of volatile fatty acid production within the Molly cow model and develop new models if the old, largely empirical models prove to be insufficient. This work, along with the efforts at FL and OH described above, are directly integrated with efforts in Objective 3.
Signaling impacts of feed additives (KS, CA,PA, OH, and ID stations)
Pre- and probiotic products offer opportunities to influence nutrient/microbe/host dynamics. Experiments in KS revealed that dietary yeast altered peripartum cow immune function (Yuan et al., 2015), and research performed in large commercial herds in CA showed increased milk fat and yield in cows supplemented with a liquid yeast product (Rossow et al., 2014) and with a live yeast product (Rossow et al., 2017). Rumen pH and circulating ketone bodies were also decreased with yeast supplementation. Work in ID has been done to better understand how feed additives can improve gut health by reducing inflammation. One such additive is exogenous butyrate, shown to decrease inflammatory response (Dionissopoulos et al., 2013) and increase VFA transport capacity in lactating dairy cows (Laarman et al., 2013). Changes in butyrate absorption is facilitated through monocarboxylate transporter 1, located on the basolateral membrane (Laarman et al., 2016). The impact of butyrate on production and absorption of colostrum is currently under investigation. Neonatal calves fed zinc daily for 14 days gained weight during a diarrhea episode vs. weight loss in placebo calves and tended to recover from diarrhea one day earlier compared to placebo calves (Glover et al., 2013).
Responses to amino acid supply (DE, KS, PA, and VA stations)
Rumen protected amino acid sources allow for us to more precisely meet dairy cattle amino acid needs, offering the potential to improve animal performance while reducing environmental nitrogen losses. Work in DE and KS have assessed bioavailability and animal performance responses to rumen protected sources of lysine, methionine, and histidine (e.g., Vargas-Rodriguez et a., 2014). Complementary work in VA has measured amino acids absorbed from microbial protein through the use of 15N infusions into the rumen.
Regulation of feeding behavior (PA, KS, MI, and Cargill stations)
Control of intake is a pivotal area of research in dairy cows. Recent data suggests total undigested NDF240 (uNDF; determined after 240 h of in vitro fermentation) is negatively related to rumen fill, and therefore, dry matter intake (DMI) in lactating cows. However, forage uNDF might have a larger impact on intake compared with by-products uNDF. Research at Cargill evaluated different levels of forage at the same level of total uNDF, and two levels of total uNDF with similar levels of forage, and determined that level of forage was better related to changes in DMI and performance than total uNDF intake (Piantoni et al., 2017a).
The daily pattern of feed intake and the effect of the timing of feed intake on rumen fermentation were investigated by PA who identified that managing the timing of feed intake is essential to stabilizing rumen fermentation (Rottman et al., 2014, 2015; Ying et al., 2015; Niu and Harvatine, 2017a,b; Niu et al., 2017). Work in KS is investigating whether feeding behavior in early lactation can predict whole-lactation outcomes (Carpenter et al., 2017), with the potential to lead to novel strategies to promote healthy adaptation to lactation. MI researchers have been identifying factors that explain the variation in residual feed intake (RFI; efficiency after accounting for differences in milk yield and body weight). They found that digestibility of fiber accounted for up to 1/3 of the differences in feed efficiency among cows when diets were high in nonforage fiber (Potts et al., 2017). Future work will continue to examine digestibility differences among cows as potential contributors to feed efficiency.
Primarily under Objective 2
Improving our understanding of the metabolic mechanisms controlling efficiency. (Cornell, PSU, KSU, WI, VA, MSU, MI, MN, TN, IN, IL, and ID Stations)
Major findings over the last 5 years include a better understanding of the regulation of gluconeogenesis in the liver, lipolysis and lipogenesis in adipose tissue, fat and protein synthesis in the mammary gland, gut health, effect of inflammation in early lactation, metabolic health during early lactation, and physiology of energy efficiency. Work has also has determined changes in residual feed intake and body condition score related to efficiency and the genetics of feed efficiency through a large collaborative AFRI grant. This work continues to provide a better understanding of the metabolic physiology of the dairy cow. Some recent work details are provided below.
Hormonal and metabolic adaptations to lactation were extensively investigated. Ehrhardt et al. (2016) showed that the naturally occurring drop in plasma leptin in transition dairy cow is a key signal promoting conservation of glucose. Giesy et al. (2012) showed that plasma adiponectin varied in quadratic across a lactation cycle, but was not changed by insulin or growth hormone (Krumm et al. 2017). Schoenberg et al. (2011) characterized dynamic regulation of FGF21 and Caixeta et al. (2017) showed that plasma FGF21 is driven by the rise in plasma non esterified fatty acids. Work in the area of hepatic lipases has uncovered new aspects of regulation including a negative correlation between liver lipid concentration and PNPLA3 abundance (McCann et al. 2014). In vitro data indicates that PNPLA3 abundance may be regulated by fatty acids (Holdorf et al., 2017). The role of methyl donors choline and methionine in hepatocytes was also investigated. In vitro work supports separate biological priorities for each of these methyl donors with choline supplementation in cell culture media resulting in decreased cellular TG accumulation, increased VLDL export, and decreased secretion of ROS into media (Chandler et al. 2017 and Zhang et al. 2017)
Additionally, the role of cellular transporters in regulating SCFA uptake in the rumen epithelium has been investigated. Passive diffusion is an important SCFA uptake pathway involved in dietary adaptation (Schurmann et al., 2014; Laarman et al., 2016), and acetate flux across the rumen epithelium is positively correlated to abundance of transporters NHE1, NHE3, and NBC1, all of which alleviate acidotic pressure in epithelial cells (Laarman et al., 2016).
Examining the biological variation in feed efficiency (MI, WI, FL, OH, and VA Stations).
Researchers have examined biological variation in feed efficiency. They found that RFI was heritable at 0.17 (Tempelman et al., 2017) and selection using genomics is feasible (Hardie et al., 2017). They also found that selecting for stature decreases feed efficiency (Manzanilla-Pech et al., 2016) and that ranking of animals based on feed efficiency is largely unchanged when fed diets divergent in starch content (Potts et al., 2015). In California, metabolic efficiency as defined by mitochondrial oxygen consumption in liver was compared to measurements of feed efficiency such as residual feed intake (RFI; Acetoze et al., 2015, 2017). They also investigated the relationship between feed efficiency and mitochondrial function and mineral supplementation in Holstein dairy cows and observed increased liver mitochondrial proton leak was associated with lower milk and protein yield. MI researchers have also provided further evidence that low starch diets promote partitioning toward milk instead of body tissues in late lactation (Boerman et al., 2015a; 2015b).
Metabolism of amino acids by the mammary gland (VA, TN, IL, PA, and WI Stations).
Work has been done to determine amino acid uptake and effect of absorbed amino acids on cellular signaling (Appuhamy et al., 2014;Arriola Apelo et al., 2014a;Arriola Apelo et al., 2014b;Crompton et al., 2014;Guo et al., 2017). Regulation of milk fat synthesis has been investigated by members in PA including the effect of inhibition by bioactive fatty acids and increasing milk fat through acetate and palmitic acid and effect of circadian regulatory systems (Harvatine et al., 2014;Rico et al., 2014;Ma et al., 2015;Davis et al., 2016;Urrutia and Harvatine, 2017a;Urrutia et al., 2017;Urrutia and Harvatine, 2017b). Lastly, the interaction of inflammation and metabolism has been investigated in KS including the effect of yeast extracts, chromium propionate, and non-steroidal anti-inflammatory compounds on metabolism and milk production (Vargas-Rodriguez et al., 2014;Bradford et al., 2015;Yuan et al., 2015;Bradford et al., 2016;Carpenter et al., 2016).
Primarily under Objective 3
Updates to the Molly model (CA, VA, and WA stations)
Molly is a dynamic, mechanistic model of ruminant digestion and metabolism used by several committee members. One of the central activities of the committee is updating this model when experimental data, such as that generated from Objectives 1 and 2, indicate weaknesses in performance.
Work from the WA station updated Molly to represent estrous cycling, IFGI and follicular growth, and degradation of estrogen and progesterone in rumen. Related work improved representation of lipogenesis and lipolysis in adipose tissue, which is an ongoing challenge with Molly.
Work from VA station updated Molly with new parameter values for rumen digesta outflow and fermentation. By including a medium particle pool and other changes, this work has improved prediction of VFA concentration and other rumen variables. Other work evaluated Molly’s ability to predict methane and feed digestibility with grass diets, and this work led to recalibration of other parameter values to improve prediction. This station also explored representing VFA interconversions based on thermodynamic driving forces, but this work did not improve prediction accuracy of VFA production.
Work from the CA station updated Molly with a new ATP stoichiometry. This stoichiometry reflects the lower P:O ratios that have now been established in bioenergetics.
Water intake and dynamics (CA station)
Recent droughts highlight the need to accurately predict of water intake and losses. The CA station developed an empirical model that predicted fresh water intake from DMI and other variables. The station also developed a mechanistic model that represented not only water intake, but also urinary water output and fecal water output.
Nitrogen, phosphorous, and methane excretion (CA, OH, and VA stations)
Minimizing excretion of N, P, and methane is key to maximizing efficiency of dairy cattle and reducing environmental impacts. Prediction of this excretion is a major interest of the committee.
Work from the CA station developed models for predicting fecal, urinary, fecal, and milk N output for different classes of cattle. Additional work evaluated of 40 models for predicting methane production, identifying the most accurate model for each geographic region of the world.
Work from the OH station developed and evaluated empirical models for predicting microbial nitrogen flow from the rumen. Model equations included terms for dry matter intake, diet digestibility, and diet chemical composition. This work is needed to reduce N excretion because more accurate prediction of microbial N flowing from the rumen will reduce overfeeding of N.
Work from the VA station developed a model to predict phosphorus bioavailability and excretion. This model included of phosphorus (phytate, inorganic, non-phytate organic) and site of digestion. This model was applied to assign bioavailability values to common feed ingredients.
Amino acid utilization for milk protein synthesis (VA station)
Work from the VA station continued efforts for increasing the accuracy of predicting milk protein synthesis. This station developed equations to predict mammary uptake of essential amino acids for milk protein synthesis. Other work expanded a model of mTOR phosphorylation, including effect of essential amino acids on phosphorylation, to predict casein synthesis in mammary gland. In related work, this station evaluated a model for predicting amino acid utilization by portal-drained viscera and the liver.
Other work (CA and MI stations)
Work from the CA station used energy balance (indirect calorimetry) records to re-derive values of maintenance and energetic efficiency of milk and tissue synthesis. The work explored both parametric and non-parametric models using a Bayesian framework. This work shows an apparent increase in maintenance over each decade of the records.
Work from the MI station determined how DMI and other variables impact feed digestibility of modern dairy cows. This work showed that digestibility decreases with increasing DMI, but at a lower rate than used by the NRC (2001). Other work developed new equations to predict digestibility of fiber, starch, fat, and protein in lactating cows.
Interdependence of Stations
- Results of research related to supply, availability and utilization of nutrients in Objectives 1 and 2 are utilized by researchers who develop models described in Objective 3.
- Joint grant applications and joint projects bridging multiple research stations result from discussions that take place during the NC2040 meetings.
- Members of the committee have collaborated as CO-PIs on several AFRI competitive grants (e.g., 2011-68004-30340, 2012-67015-19464, 2018-67015-27495).
- Work of the committee members is essential to the regular revisions to the National Research Council dairy publication.
- Efforts related to NRC development, collaborative grants, and joint projects regularly yield publications that span across at least two experiment stations. For example, a subset of publications with contributors from multiple experiment stations that were published within the previous 4 years include: de Souza et al., 2018; Firkins et al., 2015; Fowler et al., 2015; Hardie et al., 2017; Manzanilla-Pech et al., 2016; Moraes et al., 2018; Lu et al., 2015 and 2018; VandeHaar et al., 2016; White et al., 2017a and 2017b; Yao et al., 2017
Objective 1: To quantify factors that impact supply and availability of nutrients utilized for efficient milk production while reducing environmental impact
Objective 2: To identify and quantify molecular, cellular, and organismal signals that regulate intake, partitioning and efficient utilization of nutrients
Objective 3: To use this knowledge of feed properties and metabolic and molecular quantitative relationships to challenge and refine nutrient requirement models leading to more accurate feeding systems for dairy cattle
Methods for Objective 1
Work in FL will continue to elucidate why rumen microbes grow with such poor efficiency. This station had used batch culture experiment to establish energy sinks responsible for poor efficiency, and it will continue this work by using continuous culture and in vivo models. It will also continue to examine novel mechanisms for ATP synthesis. Previous work predicted novel mechanisms based on analysis of bacterial genomes sequences, and these predictions will be tested using biochemical experiments.
Researchers in OH will prepare diets that differ in ground corn relative to forage comprised of either grass hay or alfalfa hay and without or with 2% corn oil. Diets will have individual BCAA or BCVFA added in differing combinations. These dietary combinations deemed most likely to improve NDF digestibility in batch culture will be identified and fed to continuous cultures without or with BCVFA using approaches similar to those of Wenner et al. (2017). Nutrient digestibility, VFA production, and EMPS will be measured. Bacterial samples will be collected and assessed by gas chromatography linked to isotope ratio mass spectroscopy for assessment of transfer of 13C-enriched BCVFA recovered after elongation into odd and branched chain fatty acids. Dietary interactions should justify future objectives in dairy cattle with differing combinations of BCVFA or BCAA.
Methods developed at VA based on 15N tracers will be extended to assess amino acid bioavailabilty from a variety of dietary ingredients. At DE, amino acid bioavailability will be determined following the method of Whitehouse et al. (2017). Specifically, studies will employ a Latin square design with abomasal infusion of different levels of free amino acids and feeding of different levels of rumen protected amino acid sources. Plasma free amino acid response to increasing levels of abomasal amino acid infusion or increasing levels of fed rumen protected amino acid are used to generate regression lines, and slopes of the regression lines are compared using the method of Rulquin and Kowalczyk (2003) to estimate bioavailability. These results are intended to generate a feed matrix of bioavailabilty values can be developed for use in ration formulation programs.
Work at Cargill will focus on the identification and validation of nutrients that are related to dairy cow performance, and the development of models to evaluate functionality of complex systems such as the gut or the immune system in collaboration with Universities. Collaborative work at KS is enabling high-throughput screening of feedstuffs to identify those with greatest potential impacts on immune function. Additionally, KS researchers will evaluate selected feed components for impacts on in vivo immunity, including neutrophil function, immunoglobulin production, and inflammatory status.
In MI, cows will be fed diets varying in fiber or protein composition for 4 wk and then treatments will be reversed. Digestibility will be measured over 5 days at the end of each 4-wk period and compared to the rankings for residual feed intake. PA will use an established challenge model that feeds diets with increasing risk to investigate the effect of feed additives on induction of diet-induce milk fat depression. PA will also investigate differences in long-chain fatty acids on intake and digestibility and methods to increase fat digestibility. In CA, tools and supplements developed at universities in controlled herds are tested in a large commercial dairy herd environment. To determine the effect of a treatment on production in industry-relevant settings, results of small, well controlled research studies need to be confirmed with studies using commercial herds.
Work under Objective 1 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.
Methods for Objective 2
Work under Objective 2 aims to help explain the effects of dietary composition and feeding management by exploring the 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 will continue a strong basic research component as many members are funded by competitive grants to explore the underlying mechanisms which dictate dairy cattle efficiency.
Multiple members will investigate metabolic regulation during the transition to lactation. Cornell will focus on the mechanisms driving the periparturient variation in plasma FGF 21 and adiponectin including in vitro studies with bovine FGF21 promoter constructs to pinpoint both cis-elements and protein factors mediating the positive effects of fatty acids. With respect to adiponectin, Cornell will attempt to resolve how plasma adiponectin is reduced in early lactation even though adiponectin mRNA in adipose tissue remains unchanged. Cornell also intends to continue to probe the roles of both FGF21 and adiponectin using a bovine adipocyte cell culture system. WI will use in vivo transition cows studies with or with-out a metabolic challenge and in vitro utilizing primary bovine hepatocytes to investigate ketosis and fatty liver. In vivo protocols will be either a pre-partum overfed energy protocol or a clinical ketosis and fatty liver induction protocol. Primary hepatocytes isolated from neonatal Holstein calves will be exposed to various treatments (choline, methionine, fatty acids, etc) and siRNA knockdown of specific genes of interest. Media reactive oxygen species (ROS), cellular triglyceride (TG), gene expression, and protein abundance will be observed. Work at IN will utilize in vitro approaches that model hepatic metabolism to determine control loci for energy metabolism. Bovine hepatocytes and bovine MDBK cells will be used with promoter-reporter constructs and RNAi to both amplify and to restrict key reaction branch points for gluconeogenesis and fatty acid metabolism using methods described previously (Wilmanski et al., 2017). Information gained will feed into the Molly submodel for liver metabolism and refine our understanding of regulatory control and dysregulation when metabolism is compromised.
Multiple project members will investigate the regulation of milk synthesis in the mammary gland. VA developed a method of measuring cellular transport rates of 16 amino acids simultaneously and will explore the impact of changes in the composition of blood amino acids on transport rates into mammary cells. This information will be key to improvements in the post-absorptive amino acid modeling. WI will determine the role of signaling pathways on nutrient regulation of milk components synthesis with a focus on the mechanistic target of rapamycin and integrated stress response signaling pathways. Nutritional, pharmaceutical and genetic interventions will provide gain and loss of function approaches to quantify the role these pathways on milk protein synthesis in both cell culture and in vivo models. PA will investigate the effect of individual long-chain fatty acids and acetate on regulation of lipogenesis in the mammary gland and the regulation of circadian clock genes in the mammary gland. KS will investigate the effect of inflammation and non-steroidal anti-inflammatory compounds on regulation of mammary and liver function using a combination of tracer-based flux analysis, endocrinology, transcriptomics, and targeted analysis of signal transduction pathways.
The effect of a long-term exposure to acidotic environments on SCFA transport will be investigated in Idaho. A model was developed to induce subacute ruminal acidosis in calves, which we will use in planned studies.
MI will refine genomic estimates for feed efficiency and rank commerical US sires for feed efficiency and measure feed efficiency of 400 genotyped cows per year at WI and MI. Milk production, body weight changes, and feed intake will be quantified for at least 42 days during mid-lactation. Data from the feed efficiency database will be shared with other researchers and health records will be summarized to examine the relationship of feed efficiency to fertility and health. Future work will examine if differences in the energy expenditure of muscle contributes to feed efficiency using methods of Renquist et al. (2013). Semitendinosis muscle will be biopsied at the end of feeding periods in which we will rank cows for feed efficiency. CA has developed to measure mitochondrial function based on enzyme activities of complex I, IV, V and citrate synthase in blood. Future exploration of factors that will improve mitochondrial metabolism and therefore metabolic efficiency.
Methods for Objective 3
Updates to Molly
The committee will continue its tradition of updating Molly, a dynamic, mechanistic model of ruminant digestion and metabolism.
In order to make Molly available to a new generation of scientists, the CA, VA, and FL stations will recode Molly in R or another language. Molly’s current language (AcslX) is no longer supported, and Molly is in danger of being lost if not recoded in another language. Because it is free and universal, the R language is a natural choice. Matlab may be another option and was used by New Zealand researchers to recode the rumen submodel of Molly. The recoded model will be posted on the National Animal Nutrition website for use by the community. This will help ensure that the model remains viable and is improved over time.
The CA station will use data collected over the past 5 years on oxygen consumption and mitochondrial enzyme activities from cattle to develop a model of mitochondrial function in Molly. This model will be used to 1) improve predictions of fuel use and ATP production and 2) estimate metabolic efficiency. In addition, production and intake data collected on commercial dairy farms will be used to develop a simulation of a dairy herd, using Molly, to examine theoretical maximum energy and N efficiencies.
The VA station will use update Molly with key components of a postabsorptive amino acid model that is had previously developed. Updating Molly in this way will allow more extensive simulations of protein and amino acid feeding and metabolism trials. Additionally, this station will test Molly’s representation of VFA production against a matrix of VFA observations. In further work, this station will measure shifts in microbial community composition, and if they can be associated with changes in VFA production, these shifts will be incorporated into Molly.
In order to improve prediction of microbial protein supply to the cow, work at the FL station will revise the rumen submodel in Molly and improve its representation of microbial growth. Specifically, the station will update its representation of how microbial cells direct ATP energy towards growth vs. energy sinks (maintenance, synthesis of reserve carbohydrate, energy spilling). These energy sinks depress microbial growth by variable amounts, foiling efforts to predict microbial protein supply. Data generated within the past two decades, and especially the last 5 years, have quantified these sinks, enabling them to be better represented.
Single and multi-criteria nutritional optimization
Production costs, responses to nutrient supply and manure excretion of nitrogen and minerals are major determinants of the profitability and environmental sustainability of the dairy industry. The OH station will develop a series of optimization models to simultaneously minimize feeding costs and the excretion of mineral and nitrogen by dairy herds. These models will target a cost effective strategy to reduce the overfeeding of protein and minerals and provide a decision making tool to compute the costs associated with the reduction of nitrogen and phosphorus excretion by dairy herds. Further, a series of models will be developed to examine the impact of using feed sampling frequency and laboratory assays information on the overall profitability of dairy systems.
Predictive and Simulation Modeling
The OH station will use statistical and mathematical modeling to refine predictions of the supply and the requirement of metabolizable protein and amino acids by lactating dairy cows. Additionally, stochastic simulation modeling will be used to examine the adequacy and robustness of current mathematical models for the prediction of digesta flows using markers (in collaboration with the UF station). Potential modifications on these models will be examined and evaluated.
The CA station will conduct several Life Cycle Assessment (LCA) in dairy cattle to understand the impact of feed additives on environmental footprint, nutrition and productivity of dairy cattle. Both attributional and consequential LCA are planned. In addition, a mechanistic, stochastic mathematical model of protein utilization in dairy cattle will be extended and a whole animal model developed with a view to integrate it with manure/soil and landscape system models.
The CA station will also 1) develop a linear program that evaluates the water used for the production of feeds under different environmental conditions in the context of a dairy production system and 2) evaluate the variance of milk composition from the dairy cattle over several sampling days.
The MI station will refine equations to predict feed intake of lactating cows based on animal factors by using new and larger datasets. Additionally, new equations will be developed to predict feed intake based on diet characteristics.
Measurement of Progress and Results
- Development and dissemination of specific guidelines on nutrient availability from co-products and novel feed products
- Identification of new genetic markers of feed efficiency and efficiency of nutrient use
- Development and dissemination of more accurate models for predicting requirements, metabolism, and excretion of nutrients
- Provision of data to the National Animal Nutrition Program (NANP)
- Collaborative grant proposals will be submitted
- Collaborative meta-analyses will be conducted and published
Outcomes or Projected Impacts
- Improved understanding of how nutrients, microbes, and the gut interact to affect dairy cow nutrition and health
- Characterization and evaluation of novel feed products and their abilities to provide nutrients to cows
- Improved understanding of the metabolic mechanisms controlling efficiency of nutrient use
- Improved models for predicting requirements, metabolism, and excretion of nutrients
- Support of Dairy NRC planning and efforts
Milestones(2021):Within 3 years, Molly model will be recoded in R or another language. Within 5 years, it will be updated to improve representation of fuel use and ATP production, postabsorptive amino acid metabolism, and growth of rumen microbial growth.
(2023):Within 5 years, we expect to have substantially improved our understanding of energy utilization by rumen microbes and efficiency of microbial protein synthesis. We also will better characterize the rumen changes that result milk fat depression and will recommend dietary interventions to prevent milk fat depression. We will develop improved methods of predicting individual feed intake and feed efficiency. Finally, we will characterize the ability of several feed additives and pre- and probiotics to improve gut health and subsequently animal efficiency.
(2023):Within 5 years, we will develop a better understanding of how genetic, metabolic, and endocrine systems interact to control metabolism of the digestive tract and liver. We will have an improved understanding of molecular factors that contribute to individual differences in feed efficiency. We will conduct studies to determine mechanisms that regulate mammary gland uptake, use, and output of amino acids and synthesis of fat.
(2023):Within 5 years, other models described in Methods (those on nutrient optimization, life cycle assessment, protein utilization, water use, milk component variation, feed intake and digestibility) will be completed.
Projected ParticipationView Appendix E: Participation
Our first outreach goal is to disseminate novel research findings to a broader scientific audience. Our scientists conduct novel, fundamental basic research related to dairy cattle metabolism and nutrition and disseminate our research results at the American Dairy Science (ADSA) meetings to other scientists and specialists. Individuals are invited to many national and international scientific conferences to present our research. Many have given talks at Animal Nutrition Conferences across the US. In addition, basic research is used to improve and expand the development, refinement and use of nutritional decision support systems, or models, such as the NRC model, the CPM Dairy model, or the research model, Molly. This is truly the ultimate goal, that our research lead to specific, definable biomathematical equations that apply to the nutrition, metabolism, and thus efficiency and production of dairy cattle.
Our second outreach goal is to disseminate 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. The members of this committee continually discuss with our producers and allied industries to move forward in effective and meaningful research and application programs. 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 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.
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