This journal club episode comes to you from the 2024 Tri-State Dairy Nutrition Conference. The paper is “Methane in the context of circular dairy farming” from the conference proceedings.

What is circular dairy farming? The concept is that instead of extracting or using natural resources and then discarding the wastes in a linear kind of fashion, economies should try to be increasingly circular. This would include the concepts of reusing, recycling, upgrading, upcycling, etc. Traditionally, the focus on methane was about the inefficiency and leakage of energy and finding a way to minimize that from the perspective of energetic efficiency and productivity. More recently, the focus on decreasing methane has been the environment. (3:19)

Dr. Newbold talks about the trade-off between circularity and methane. High fiber diets produce more methane than high starch diets. Adding fat to diets can also decrease methane production. However, starch and fat are human edible so if we leave starch and fat in feeds to decrease methane in dairy cattle, that leaves less starch and fat for human consumption. The concept of “local” also plays into circularity, whether that be feed production or milk processing. (7:01)

What are the metrics of circularity? Two approaches to this present in the literature. The first is human edible efficiency: how much human edible food are we producing? In a dairy setting, the measurement would be how much human edible food are we putting into the cow compared to the amount of human edible food coming out of the system? The second metric is the alternatives for land use. (10:45)

What is the best way to express methane production? Dr. Newbold shares three, and they are generally used in different contexts. First is methane production, usually presented as grams per cow per day. This is an easily scalable measurement, but may not be the best or easiest way to manage interventions on-farm. The second common metric is methane yield which is generally expressed as grams per kilogram of dry matter intake. Lastly, methane emissions intensity is grams of methane per kilogram of milk. (12:26)

When considering the human edibility equation, the denominator consists of the human edible content of the feed. In principle, depending on how hard you worked and how much money you spent, you could extract some of the starch, fat, and protein and use it for human food. However, there's no consensus in the literature about this kind of edibility coefficient. In other words, what proportion of the protein in soybean meal or the proportion of starch that's left in wheat middlings or distillers grains is human edible? Greater consensus about what is and what is not human edible would actually be quite useful in allowing for better and more consistent calculations. (18:29)

Dr. Newbold gives examples of relative efficiency comparing U.S. dairy production, a grass-based system, and a tropical grass based system. Each of these have a different human edible efficiency and a different amount of methane produced. (19:59)

When it comes to lowering the environmental impact of milk production, don't focus on one metric in isolation of the rest of them. If you're setting off in a particular direction, whether that's trying to drive methane down or milk production up, think about the potential trade offs and unforeseen consequences. (32:12)

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This episode comes to you from the 2024 Tri-State Dairy Nutrition Conference, where Balchem sponsored a Real Science symposium titled “New Discussions in Amino Acid Nutrition.” Each of our guests presented at the symposium, and their presentations can be found at balchem.com/realsciencemedia

Dr. Van Amburgh presented “Amino Acid Nutrition for Maximizing Milk Component Yield.” When considering nitrogen efficiency, we generally compare intake nitrogen, which includes non-protein nitrogen, against milk nitrogen. In high producing cows, aggregate amino acid values are running about 70 to 73% efficiency. But when we work that up to total intake nitrogen, then we're down to 30 to 35% efficiency range. How do we reconcile ruminal nitrogen requirements to a point where we can optimize the capture of recycled nitrogen and reduce the amount of nitrogen that's being excreted in the urine? (2:27)

Dr. Hanigan presented “Understanding Amino Acid Bioavailability.” Our current methods for measuring bioavailability don’t all have the same precision. One of the classic methods, intestinal disappearance, has very low precision. Methods that rely on dilution of a marker or a label in blood or milk have much higher precision. Dr. Hanigan’s lab has worked to modify a carbon-13 labeled amino acid method to allow for evaluating changes in the supply of amino acids in the diet. (5:01)

Dr. Lee presented “Current Understandings of Lysine Nutrition in Dairy Cattle.” Rumen-protected lysine has more variable responses than rumen-protected methionine or histidine. Amino acid requirements were developed based on the role of amino acids as the building blocks of protein. But there are many roles of amino acids which may influence their requirements. Dr. Lee suggests including that type of information in our modeling may increase the consistency of responses to feeding rumen-protected lysine. (11:24)

Dr. Hristov presented “Histidine: A Limiting Amino Acid for Dairy Cows.” His group has worked with rumen-protected histidine to develop a dataset to define requirements. Microbial protein has considerably less histidine than methionine yet they are secreted at about the same level in milk and are metabolized similarly. All this together points to a higher histidine requirement. (18:02)

The panelists agree that the advent of genomics have resulted in a rapid change in high producing cows and with that, their amino acid requirements (and other nutrients) are also changing. It’s a challenge for feeding and nutrition programs to keep up with rapid genetic change. (21:02)

A question was posed by the audience about how Dr. Van Amburgh used amino acids to increase butter fat. In the research he presented, the diets did not overfeed fat and fed a blend of fatty acids, and also increased the sugar and pulled back the starch. (28:35)

A discussion of histidine follows, including its unique body reserves, its role in hemoglobin concentrations, and its potential impacts on metabolic energy efficiency (34:08)

Dr. Zimmerman asks about plasma histidine in very early lactation cows. Dr. Hristov is currently conducting a fresh cow experiment to assess this. His hypothesis is that because of low dry matter intake and high metabolic demand for amino acids, there will be a response to histidine supplementation. Dr. Lee agrees and feels that the fresh cow stage may be one of the most practical ways we can utilize rumen-protected histidine (39:39)

A question from the audience about the use of blood meal in lower protein diets sparks a spirited discussion among the panelists. (41:55)

In closing, each panelist provides a takeaway. Responses range from bioavailability of rumen-protected products to challenges to progress for ruminant amino acid research to comparing biological potential and economic response. (46:58)

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