For decades, crude protein was one of the primary measurements that nutritionists used to evaluate soybean meal. But as dairy nutrition becomes increasingly precise, researchers and nutritionists are looking much deeper into what a feed ingredient delivers to the cow.
Today, the discussion includes metabolizable protein, individual amino acids, digestibility, energy, protein fractions, ingredient variability and processing. The shift reflects a broader goal in dairy nutrition: provide cows with the nutrients they need as precisely and consistently as possible while reducing unnecessary feed costs and nutrient losses.
Thomas D’Alfonso, Ph.D., Worldwide Animal Nutrition Focus Area Director for the U.S. Soybean Export Council (USSEC), and Leoni Martins, Ph.D., Assistant Clinical Professor of Precision Dairy Nutrition at Penn State University, recently spoke with The Cattle Site Podcast’s Sarah Mikesell about how research is changing the way nutritionists evaluate soy and formulate dairy diets.
Both see ingredient consistency as a critical part of precision nutrition, particularly as researchers develop a more sophisticated understanding of how cows use protein and individual amino acids.
Crude protein tells only part of the story
The move away from crude protein starts with understanding what the measurement represents.
Crude protein analysis does not directly measure the protein or amino acids contained in an ingredient. Instead, traditional laboratory methods measure nitrogen and use a coefficient to estimate crude protein.
“Crude protein has been a core quality measure for more than 100 years, and the methods that we use are also about 100 years old,” D’Alfonso said. “What's really important is to measure the essential amino acids and the energy that's available to the animal for maintenance and productive use.”
For modern dairy nutrition, a crude protein value provides limited information about what ultimately matters to the cow.
Martins said nutritionists need to understand what happens to protein throughout that digestive process. When a cow consumes protein, some is degraded in the rumen and used by rumen microbes, while another fraction escapes rumen degradation and passes into the intestine. This led nutritionists to move from crude protein toward measurements such as rumen degradable protein (RDP) and rumen undegradable protein (RUP).
The science has continued to advance toward metabolizable protein, which provides a better understanding of the protein reaching the intestine and ultimately becoming available to the cow. More recently, nutritionists have taken another step by evaluating individual metabolizable amino acids and identifying those that may limit production.
“Moving away from crude protein to RDP, RUP and then to metabolizable protein gives us a better picture of which amino acids are being absorbed and are available for the animal to perform its functions, like milk production, maintenance and growth,” Martins said.
Soy quality starts before formulation
As nutritionists become more precise about what a cow requires, knowing what an ingredient can consistently provide becomes increasingly important. For soybean meal, D’Alfonso said that begins with understanding the origin of the soybeans and how they were handled and processed.
USSEC has monitored soybean quality from the U.S., Brazil, Argentina and other soy producing regions. D’Alfonso said differences in growing conditions, harvest moisture and processing can influence the quality of the beans entering the feed supply chain.
U.S. soybeans are naturally dried in the field, reducing the potential for heat damage that can occur when high-moisture beans require more intensive drying. The practical message for nutritionists is to evaluate the nutrients the cow can actually use rather than relying heavily on a single compositional measurement.
Analytical tools can help. Near infrared spectroscopy (NIR) is increasingly being used around the world to measure quality characteristics associated with feed ingredients.
Ultimately, however, D’Alfonso said dairy producers also see ingredient quality reflected in their cattle.
“At the end of the day, the animals will tell you,” he said. “If they're not getting the nutrients they need, you'll see suboptimal performance.”
Precision nutrition is really about variation
Precision nutrition is often associated with sensors, automation, robotics and other technologies, but Martins said the fundamental concept is much simpler.
Precision is about managing variation and uncertainty. In dairy nutrition, two important sources of uncertainty are the cow and the feed. Animal requirements change with production, genetics, environment and other factors. At the same time, feed ingredients can vary in nutrient composition and availability.
The objective is to understand both sides well enough to more closely match nutrient supply with nutrient requirements.
“In an ideal scenario, as a precision nutritionist, what I want to do is to deliver the exact amounts of nutrients that the animal needs to perform at its optimum,” Martins said. “Too much creates inefficiency and can increase nutrient excretion, and too little can limit animal performance. So, precision is how we manage the uncertainty.”
D’Alfonso described precision nutrition similarly, saying nutritionists need to know both the requirements of the animal and whether the feed ingredients and feeding system are actually supplying those nutrients.
That makes ingredient quality control an integral part of precision feeding.
Consistency takes one variable out of the ration
Determining the nutrient requirements of a dairy cow is not always straightforward.
Researchers have developed good estimates for many maintenance and production requirements, but Martins said there are still biological functions that are more difficult to quantify.
One example is immune function. Researchers do not yet fully understand how much individual amino acids may be partitioned toward an immune response rather than milk production or other functions. This makes the animal side of the precision nutrition equation inherently complex.
Feed quality, however, is a variable nutritionists can more readily measure and manage.
“Making sure I have a consistent product that will deliver those nutrients that I formulated for, that's a huge first step towards precision nutrition and meeting the requirements of my animals,” Martins said.
D’Alfonso said ingredient variability has long been incorporated into ration formulation using safety margins. When an ingredient has significant variability, nutritionists may discount its nutrient contribution because they cannot confidently assume the average value will be present in every load.
For example, an ingredient that averages 3% lysine might be credited with only 2.5% or 2.7% during formulation because of variability available to the animal. However, more consistent ingredients require less discounting.
D’Alfonso said lower variability in soybean meal derived from U.S. Soy can therefore translate into feed cost savings because nutritionists can formulate with greater confidence in the nutrient values they are using.
Processing adds another layer of variability
Soy quality does not stop with the bean. How soybeans are processed can substantially influence the final ingredient fed to cows.
Martins said commercially processed soybean meal provides an example of a product for which nutritionists can generally expect a consistent nutritional profile. More variability can enter the system when whole soybeans are harvested and processed on individual farms.
Roasting and other on-farm processing methods require producers to make decisions that can influence the resulting nutrient profile. If the process is not well controlled, variability can increase. That means producers feeding whole soybeans need to consider where the beans originated, how they were processed and how the resulting product will be incorporated into the ration.
“Every time that we take soybeans out of a processor that has learned how to process the beans and is consistent with that process, we're going to increase our chances of having a more inconsistent product,” Martins said.
D’Alfonso said processing quality and raw material quality must work together.
“You need to start with a high-quality raw material because you can't fix what's already broken,” he said. “A sophisticated processing system cannot reverse nutrient damage that has already occurred in the bean.”
Research needs to reach the farm
As dairy nutrition becomes more complex, translating research into practical recommendations becomes increasingly important.
Penn State research examining soybeans and feed variability provides one example. At a Penn State nutrition workshop, more than 120 nutritionists participated in a hands-on session examining the implications of uncontrolled soybean processing on farms. The discussion connected processing variation with outcomes including milk production, profitability and environmental nutrient excretion.
“These collaborations between universities and the industry are really important for disseminating our knowledge that we've been generating,” Martins said.
D’Alfonso said USSEC uses a similar approach globally through its Soy Excellence Centers’ workshops and online educational programs designed to bring information and research to producers, nutritionists and other animal agriculture professionals.
He said both basic and applied research are important because producers ultimately need information they can translate into feeding decisions.
More to learn about how cows use nutrients
Despite significant advances in dairy nutrition, Martins said researchers still have considerable work to do in understanding variation among cows and how nutrients are partitioned after absorption.
Amino acids absorbed into the bloodstream do not automatically go toward milk production. Multiple tissues are working simultaneously and competing for those nutrients for different biological functions. Understanding that system more precisely represents a longer-term research challenge.
Feed processing and ingredient variability, meanwhile, provide opportunities for research that can be applied more immediately on farms.
Martins said work with whole full-fat soybeans is already helping producers determine whether their current processing systems are producing the expected results and where changes may be needed.
Researchers are also beginning to look beyond traditional nutrients such as protein and energy. Soy contains bioactive compounds, while soybean fatty acid composition may also have implications for animal health and production. Martins sees potential for that research as dairy cows contend with heat stress, immune challenges and the metabolic demands of high production.
D’Alfonso agreed that the industry is continuing to discover nutritional characteristics of soy that extend well beyond crude protein.
“It's about the amino acids and the availability to the animal. And it's not just calories, but it's the source of calories,” he said.
Fat quality, fatty acid profile, fiber, isoflavones, bioactive peptides and other compounds are all part of the broader nutritional package.
“The nutrient bundle in soy has so much to offer,” D’Alfonso said.
Control what can be controlled
For dairy producers, the value of that research ultimately comes down to managing a complicated biological and production system more effectively.
Farms face variables every day that producers cannot completely control. Weather changes. Cows differ. Health challenges occur. Forage quality fluctuates.
“Your feed ingredients don't need to be one extra variable that you want to deal with,” Martins said.
“Consistency with feed ingredients that you use and understanding what those feed ingredients are will set you up for success because now you know what you're giving to your cows,” Martins said.
That philosophy captures where precision dairy nutrition is heading. The industry is moving beyond simply asking how much crude protein is in an ingredient toward understanding what nutrients are present, how processing affects them, how consistently they are supplied and, ultimately, how much the cow can use.