Jacquelyn Prestegaard: When cows teach us about much more than just milk

The following story was written in April 2018 by Chiron Anderson in ​ENGL ​4824​: Science Writing ​as part of a collaborative project that included the English department, the Center for Communicating Science, ​the ​Fralin Life Science​ Institute​, and ​Technology-enhanced Learning and Online ​Strategies (TLOS).

Jacquelyn Prestegaard conducts her research on a farm that’s home to nearly 400 dairy cows. But these cows are used for more than just milk. They serve as great tools for education and outreach at the Dairy Science Complex at Kentland Farm, Virginia Tech’s dairy research facility located just 15 minutes outside of campus.

    Prestegaard moved to Blacksburg in 2017 to begin her doctoral program in Virginia Tech’s Dairy Science department, just one day after she earned her master’s from the University of Missouri. Her master’s research, on amino acid nutrition in beef cattle, provides a strong grounding for her current project, but her love of working with animals goes all the way back to her childhood. Prestegaard grew up on a beef cattle farm and became interested in how nutrition impacted their growth early in her life. In the spirit of Ut Prosim, she hopes her research will help dairy farmers across Virginia.

    “The ultimate goal of dairy cattle nutritional research… is to give back to the agricultural community... and to serve our stakeholders. In this case our stakeholders are dairy farmers throughout Virginia [and across the US],” she explained.

    Efficiency is the name of the game for dairy farms.  The price of milk is currently low and dropping, and many farms are struggling to stay afloat in the presence of a nationwide milk surplus. An overarching research theme in Dr. Mark Hanigan’s laboratory, where Prestegaard conducts her work, is to improve the efficiency by which feed is converted to milk. Doing so can lower milk production costs and help the environment at the same time.

    Prestegaard is working toward this goal by researching amino acid nutrition in dairy cattle. Amino acids are the building blocks from which all proteins are built, forming long chains that fold into an incredible variety of structures to carry out biological processes. Without a good balance of amino acids and energy in the cow’s diet, her potential for milk production decreases.

    There are several concerns when formulating diets for dairy cattle that all need to be balanced according to the farmer’s priorities, Prestegaard explained. One is maximizing milk production through nutrition; the more milk a cow produces, the more the farmer can sell. Another is making milk production as cost effective as possible; the less expensive milk production is per pound, the greater net profit a farm will make. Finally, the environmental impact of the cow’s digestion of the feed may also be considered.

    To balance these goals, Prestegaard’s laboratory group not only considers what goes into the cows, but, to put it delicately, what comes out. Nitrogen and phosphorus in cow manure can accumulate in runoff that flows into the local watershed and potentially damages these environments.

    While proper cleaning and storage procedures can mitigate these effects from farms, minimizing the amount of nitrogen and phosphorus that is excreted by the cows themselves is an important factor.

    “Any [nutrients] that [the cows] don’t put into making milk, growing, or just maintaining themselves overall will be wasted,” Prestegaard said.

    One complicating factor is the biology of the cows themselves. Unlike humans, cows have a stomach with four compartments, each performing a different role in the digestive process. The largest of these compartments is known as the rumen, and it acts as a fermentation vat for feed. The rumen houses a large population of bacteria, protozoa, and fungi that break down feed and absorb the resulting nutrients and excrete waste products resulting from fermentation of the nutrients. This process makes predicting uptake of amino acids much more complicated for cows and other ruminants than for swine or other monogastric (single stomached) animals.

    The dairy complex at Kentland has a rich earthy smell, mixed with the unmistakable scent of the cows themselves. From the pristine milking parlor to the waste management system, a sense of organization and clarity of design is present throughout the complex. One reflection of this systematic approach is the set of Calan gates used for many nutritional studies in the Dairy Science department.

    Each Calan gate will only open when the cow assigned to a particular dietary treatment approaches the gate. The gates open using an RFID (radio frequency identification) neck collar on each individual animal, and the cows quickly learn which gate is their own. This system allows Prestegaard and other researchers in the department to test multiple dietary treatments at a time while ensuring each cow has a consistent diet for the course of the trial. Prestegaard’s future project will analyze the effect of multiple diets on milk production, blood amino acid content, and nitrogen metabolism. This data will then be incorporated into mathematical nutrition models developed in Hanigan’s laboratory.

    Another aspect of Prestegaard’s work is testing whether commercially available “rumen-protected amino acids,” purified forms of the acids protected by a layer of fat, are nominally able to survive degradation by bacteria in the rumen. One way to measure how well they really survive the rumen, and how well the amino acids are subsequently absorbed by the cow, is to insert them directly into the rumen of the cow for a period of time. Then the fraction that isn’t degraded by the microbes is removed from the rumen by the researcher and infused directly into the next portion of the digestive tract. Blood samples taken during the experiment show whether those subsequent amino acids reached the blood stream. This experiment requires cannulated cows--cows that have undergone a common surgery in nutritional research that allows researchers to access the rumen directly via a plug known as a cannula.

    Prestegaard and her colleagues are working with Virginia's agricultural community to meet their needs as directly as possible. She is working with Hanigan, her advisor, as well as with Dr. Tiffany Drape from Virginia Tech’s department of Agricultural Leadership and Community Education to organize a survey of nutritionists throughout the state. Their goal is to find out how nutritionists use amino acids  when formulating diets. At the same time, the nutritionists will be able to communicate their own priorities, allowing the survey team to report their findings with the nutritionists’ focuses in mind.

    “We want it to be a two way street… [we want to learn from them as much as we want them to learn from us]. We don’t want to just tell them [if] they’re doing [something] wrong, or what we think they’re doing wrong,” Prestegaard said.

    In the future, her laboratory plans to launch a webpage hosted on the Virginia Cooperative Extension page, allowing dairy farmers and nutritionists across the country to access and understand their research. The webpage will include past and current amino acid nutrition research, nutritional models and how to use them, and several animated figures portraying her laboratory’s research created in collaboration with Professor Dane Webster of University of Colorado-Denver.

    Prestegaard and the colleagues in her laboratory will continue to refine and expand nutrition models in the future as their experiments yield new data. As for herself, she hopes to give back to the scientific community by teaching animal science courses someday and help to inspire the next generation of students.

    “What I would want the public to know about my research, or research in [animal science] in general is that [we work] in this field because we love it, because we really enjoy working with the animals, collecting data, and making new discoveries," said Prestegaard. "[I]t’s a really rewarding process, and we wouldn’t be doing it if we didn’t enjoy it.”

Photos courtesy of Jacquelyn Prestegaard, Tricia Lombardi, and Pearson Scott Foresman (public domain).