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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