Real Science Exchange-Dairy

Dr. Penner presented “Progress in the gut: What we know about ‘gut health’” to lead off the symposium. He highlights using rumen acidosis as a model for gut health, focusing on key structures and how paracellular permeability is maintained or dysregulated, absorptive function, and microbiology. He notes that rumen acidosis affects other parts of the gut besides the rumen. (4:52)

Dr. Laarman wrapped up the  symposium with “Gut health in ruminants: Where to from here?” He agrees with Dr. Penner that we need to look beyond the rumen at all other gut organs. His group has researched rumen acidosis in calves and how it’s linked to hindgut acidosis and pH dynamics. Calves behave very differently from cows in this model. Gut health begins from birth and is the whole tract, not just the rumen.  (7:35)

Work in Dr. Penner’s lab showed that inducing inflammation in the mammary gland actually tightened permeability in the GI tract, which was opposite of their initial hypothesis. Dr. Baumgard’s lab found similar results in a heat stress model, and Dr. Laarman echoes that his group has also found this result.  The panel discusses possible mechanisms of action. Dr. Penner explains that diet may also have an influence on gut permeability. (11:01)

The panel talks more about what we know and don’t know about gut health. We probably know which regions of the gut are most likely to be affected by challenges, what those impacts are, how fast those gut changes occur, and how nutrient absorption can be affected by challenges. The group hypothesizes that pH alone does not have a negative effect, but if low pH occurs at the same time as other signals or molecules, then pathology happens. Dr. Laarman shares some of the observations his group has made with calves, which withstand low pH that would kill a mature cow if she experienced it. (18:40)

Guests talk about some of the reasons why we know less about ruminant gut health compared to monogastric species. They also visit about the microbiome and how perhaps what the microbiome is doing and producing is more important than who all is present in the microbiome. (23:44)

Panelists share their take-home thoughts. (29:33)

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Recommendations for identification and selection of bioactive compounds to develop antimethanogenic feed additives. Dr. Yáñez-Ruiz (8:23)

How can we search for molecules that modify how feed is fermented in the rumen? Conventionally, we have used scientific literature to look for plant extracts and compounds that have been researched before. Now, we have computational technology that offers opportunities to model how molecules interact with rumen microbes. Once a candidate compound is selected, in vitro tools can be used to test dose responses before animal experiments. 

Recommendations for testing enteric methane-mitigating feed additives in ruminant studies.

Dr. Yáñez-Ruiz for Dr. Alexander Hristov (17:07)

Once compounds have been identified and selected, they need to be tested in the animal. These experiments are costly and best practices for experimental design, animals used, diets fed, delivery of the test compound, and measurement of methane should be followed. Some of these guidelines are strongly linked to the regulatory aspects that provide requirements for how in vivo trials need to be conducted. 

Feed additives for methane mitigation: Modeling the impact of feed additives on enteric methane emission of ruminants—Approaches and recommendations. Dr. Bannink (22:43)

Once experimental data is collected, it can be used to develop models to predict how effective an additive is, how it works, and its relevance. The intention is to quantify how an additive will work if you feed it to an animal. This can be complex due to variation among different datasets and natural fluctuation in methane production in the animal. One factor that plays a big role in the effectiveness of additives is the type of diet that animals are fed. 

A guideline to uncover the mode of action of antimethanogenic feed additives for ruminants. Dr. Belanche (30:03)

Understanding the mechanism of action for methane mitigants is challenging. We know some compounds work to reduce methane, but we don’t know how or why they are working. There are five main types of additives when grouped by mode of action: modify rumen fermentation to decrease hydrogen production; methane inhibitors that act specifically against methanogens; inhibit enzymes common to all methanogens; hydrogen sinks to redirect hydrogen away from methanogenesis and toward other metabolic pathways; and promote methanotrophs that oxidize methane. The most effective are methane inhibitors, which decrease methane but don’t increase animal productivity. Combining a methane inhibitor with a hydrogen sink may help redirect hydrogen and result in improved animal productivity.

Regulations and evidence requirements for the authorization of enteric methane-mitigating feed additives. Dr. Tricarico (41:22)

There are as many regulatory systems as there are jurisdictions. Two concepts that are shared across jurisdictions are regulatory status/legal classification and intended use. While each jurisdiction requires some legal classification of a feed additive compound, each has a different criteria base from which they classify products. For example, “inhibitor” is a legal classification in New Zealand, but doesn’t even exist in other jurisdictions. Sometimes, the same word may mean different things in different jurisdictions. Authorization of a compound is not a blanket authorization, it is an authorization of the intended use of the compound. This specificity is critical for all involved to understand.

Feed additives for methane mitigation: How to account for the mitigating potential of antimethanogenic feed additives—Approaches and recommendations. Dr. del Prado (49:42)

A major challenge in this area is what kind of accounting system will be used: farm level, lifecycle analysis, carbon markets, national greenhouse gas inventories, etc. An accounting system needs to be well tailored from the type of experimental data available to the complexity used on the scale of the method. Experimental data, modeling, and accounting move hand-in-hand. 

Panelists share their take-home thoughts. (58:57)

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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)

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Dr. Ricklefs-Johnson talks about bone health and the cardiovascular health benefits of cheese. Calcium, phosphorus, and vitamins D, K, and B12 are all important for bone health, and cheese is a good source of each. In the past, saturated fat in cheese would have been demonized, but research is finding that saturated fat isn’t created equally across all food types, and cheese has many unique fatty acids. Cheese consumption is associated with reduced risks of coronary heart disease, cardiovascular disease, and stroke. Cheese contains bioactive peptides that appear to help lower blood pressure. (4:18)

The panel discusses the mechanisms of action of cheese consumption on cardiovascular health, how much cheese is recommended daily, and whether different cheeses have different health benefits. Dr. Ricklefs-Johnson explains that the protein in cheese is primarily in the form of casein, rather than whey. Casein had been less utilized as it was thought harder to digest, but more research is showing the benefits of casein in muscle recovery and helping with sleep. (8:27)

Research supports that calcium from cow milk sources is more bioavailable compared to supplements or fortified calcium in plant milks. Cheese is also unique as a dairy food that contains vitamin K, which works in conjunction with vitamin D and calcium for maintaining bone mass. (15:07)

The panel visits about some of the other presentations at the symposium, including feeding cows to influence vitamin K or fatty acids in the milk and how to get the word out about the health benefits of cheese. (19:16)

Panelists share their take-home thoughts. (26:29)

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Dr. Rico’s presentation was titled “Of cows and bugs: Using insects as alternative feeds in dairy cattle nutrition.” He gives an overview of his presentation, noting that while insects are not a major focus of US dairy nutrition, they are of interest in other parts of the world as a protein source to substitute for soybean or fish meal. (2:12)
Dr. Dou’s talk was “Alternative feed for livestock: Opportunities and challenges to support a circular food system.” She explains that a typical agriculture/food system is linear: take, make, and waste, which generates a lot of food residues. Her research aims to recover and recycle some of the food residues from other industries and evaluate their suitability for livestock feeding. (3:51)
Dr. Pinotti’s presentation was titled “Alternative foodstuffs in dairy ruminant nutrition: Basic concepts, recent issues, and future challenges.” His research focuses on using “former food” for livestock feeding and feeding insects not only as a protein source but also as a potential mineral source. (5:38)
Dr. Pinotti talks about the challenges around variability in alternative feedstuffs. He goes on to describe some of the bakery byproducts he has used in research rations. He calls them fortified versions of cereal. They contain quite a lot of starch and also contain a lot of fat. These ingredients are ideal for young monogastric animals and also have utility in lactating dairy cow diets. The panel discusses the EU animal protein ban and whether similar restrictions exist for animal fats. (10:16)
Dr. Rico notes that insects contain between 40 and 70% protein, depending on the type of insect. Crickets, mealworms, and black soldier fly larvae are the most popular. The fly larvae have a higher fat content compared to crickets and are a good energy source for monogastrics like pigs, chickens, or fish. Less is understood about the feeding value of insects in ruminant diets, and Dr. Rico’s lab has been conducting experiments to help define this in dairy cattle. He notes the chitin content of insects is a unique challenge due to its indigestibility. It comes out in the NDF fraction in a nutrient analysis, but it is animal fiber, not plant fiber. (21:27)
The panel talks about the scalability of insects as a protein source and confirms that the theory that insects are a cheap protein source is different from reality at this time. The group talks about small-scale insect projects at universities and in Africa. (27:17)
Dr. Pinotti explains that insects are quite good at accumulating minerals, bad and good. His group conducted an experiment using sodium selenite as the substrate and the insects made selenocysteine and selenomethionine. Future research will include zinc as well as selenium in the substrate, and insects will be fed in an in vivo trial to verify bioavailability. He does not envision issues with chitin interfering with bioavailability since the insects incorporate the minerals into amino acids. (34:27)
Dr. Rico talks about the amino acid and fatty acid profiles in insects. Essential amino acid content is relatively similar to other common protein sources. Insects contain higher levels of lauric and myristic acids than other common sources which could pose a challenge for lactation diets. He explains that there is a low-fat source of black soldier fly larvae with around 12% fat, compared to 30% in the full-fat version. The panel talks about variability in protein and fat content by insect type and the substrate the insects were grown on. (37:35)
Dr. Dou describes some of her circular feed research using fresh cull fruit (kiwi, citrus, apples; delivered daily) blended into the TMR. Later, she also ensiled the fruit with dry hay in an effort to preserve the fruit before spoilage. Dr. Pinotti notes that he has used cull material from a salad plant as feed as well.  (44:31)
Dr. Dou reports that one-third of food produced for human consumption never makes it to the human stomach. Globally, it’s estimated that 1.6-1.9 billion tons of food are lost and wasted each year. The panel talks about the biggest challenges keeping us from using more former food products in livestock feeding. (50:54)
Panelists share their take-home thoughts. (59:51)
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