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Real Science Exchange-DairyAuthor: Balchem Animal Nutrition & Health
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Exploring Flexibilities in Protein Nutrition for a Sustainable Dairy Industry with Dr. Kelly Nichols, University of California-Davis, and Dr. Susanna Räisänen, Aarhus University
Episode 193
Tuesday, 10 March, 2026
Dr. Nichols opens by outlining her background in protein nutrition research spanning Canada, the Netherlands, industry R&D, and now academia at UC Davis. Her research has focused on mammary amino acid metabolism, nitrogen efficiency, and the interaction between protein and energy supply in dairy cattle. (1:00–4:05) Dr. Räisänen shares her path from Penn State to Finland, Switzerland, and now Aarhus University, where she is leading research within a large, multidisciplinary project focused on lifetime nitrogen efficiency in dairy systems. Her current work examines early lactation protein supply and rumen nitrogen balance. (7:32–10:07) The discussion begins by establishing why protein nutrition plays a central role in sustainability. Ruminants are net protein producers, converting low-value feeds into high-quality milk and meat protein. However, inefficiencies in nitrogen utilization lead to urinary nitrogen excretion, contributing to ammonia emissions, nitrous oxide production, and nitrate leaching. Improving nitrogen efficiency, therefore, directly impacts environmental outcomes. (12:28–14:17) The group discusses geographic differences in nitrogen regulation. European countries like the Netherlands and Denmark face intense scrutiny due to high livestock density on limited land. Similar regional challenges are emerging in concentrated U.S. dairy regions such as California’s Central Valley and parts of the Midwest. (15:17–18:19) Dr. Nichols introduces the concept of metabolic flexibility—the ability of ruminants, and especially the mammary gland, to utilize different nutrients and metabolic pathways depending on supply. This flexibility helps explain why responses to protein supplementation are not always black and white, and why traditional limiting amino acid theory does not consistently predict milk protein responses. (24:58–26:23) The conversation explores early lactation “protein boost” strategies inspired by post-ruminal amino acid infusion studies. Dr. Räisänen describes ongoing work using targeted concentrate supplementation to mimic infusion responses. Preliminary data suggest substantial early lactation milk yield responses, similar to infusion studies, when protein is delivered in a separate concentrate rather than blended into a TMR. (28:33–31:16) Dr. Nichols discusses three key areas of flexibility highlighted in her webinar: Energy source interactions (glucogenic vs. lipogenic supply), Rumen nitrogen balance, and Mammary gland amino acid metabolism. (32:21–33:50) The panel explores how feeding systems may influence metabolic responses. PMR systems with separate concentrate feeding may allow temporal and metabolic “choice,” potentially improving efficiency compared to uniform TMR feeding. Robotic milking systems and automated concentrate feeders offer opportunities for more individualized protein nutrition strategies. (35:00–37:57) Amino acid discussions highlight how flexibility challenges the traditional limiting amino acid model. Milk protein synthesis is not consistently limited by one amino acid, and mammary uptake patterns show that amino acids can serve multiple roles beyond direct incorporation into milk protein. Lysine, leucine, and histidine are discussed as examples of amino acids whose responses may vary depending on metabolic context. (41:07–45:25) The group also examines energy source effects on nitrogen partitioning. Lipogenic diets (e.g., supplemental fats) may alter amino acid metabolism differently than glucogenic diets, but more research is needed to fully characterize these interactions. (49:24–53:11) Dr. Räisänen emphasizes the importance of rumen microbial protein synthesis and improving prediction models for digestible amino acid supply. Better understanding and measurement of microbial protein output could significantly improve feed evaluation systems and nitrogen efficiency modeling. (54:04–56:05) Dr. Nichols highlights endogenous nitrogen recycling and urea transport back to the rumen as another underexplored area. Improved mechanistic understanding of recycled nitrogen could refine models of rumen nitrogen balance and reduce overfeeding of dietary protein. (1:00:46) The episode closes with a discussion of cow-to-cow variation in nitrogen efficiency and the potential for individualized feeding strategies to optimize the marginal efficiency of protein use. (1:02:00) Please subscribe and share with your industry friends to invite more people to join us at the Real Science Exchange virtual pub table. If you want one of our Real Science Exchange t-shirts, screenshot your rating, review, or subscription, and email a picture to anh.marketing@balchem.com. Include your size and mailing address, and we’ll mail you a shirt.
