Research Note
Courtesy: A.F. Ortega at ADSA 2023 & 2022 Cornell Nutrition Conference Proceedings
Amino Acids — EAA & NEAA:
Meeting Nutritional Needs But Still Falling Short of Potential?
The rapid pace of advances in dairy genomics is an ongoing challenge for nutritionists, says Cornell’s Dr. Mike Van Amburgh.
“Modern, high producing cows continue to show unrealized potential in lactation performance and components output. They’re already light years ahead of their recent ancestors, which amplifies today’s need for precision nutrition.”
More precise prediction of requirements for essential amino acids (EAA) featured prominently at the recent ADSA 2023 meeting, which included a metanalysis (1246M) comparing current dairy feed programs (NRC 2001, NASEM 2021, CNCPS v6.5.5).
EAA priorities
Van Amburgh notes that both the report of National Academies of Sciences, Engineering and Medicine (NASEM 2021) and the latest iteration of Cornell Net Carbohydrate and Protein System (CNCPS v7) prioritize EAA in diet formulation as follows: (1) methionine, (2) lysine, (3) histidine, (4) leucine, and (5) isoleucine.
“We still need to fully develop the sensitivity of individual EAA,” he adds, “but given the opportunity to formulate for all EAA, these AA are likely a good place to start.”
Van Amburgh points out that the CNCPS v7 model estimates optimum EAA requirements per unit of metabolizable energy on a nitrogen basis rather than crude protein. There’s a goal to more fully describe “efficiency of use” of EAA. However, he says, this feature requires much more work as it will likely vary by homeorhetic demands (dry, close-up, fresh, established lactation periods).
Moving your cheese (up)
Van Amburgh adds that collaborative research with dairy food scientists suggests what is possible by focusing on “true AA” requirements for high-producing cows: Milk fat up from 4.1% to 4.6% or 4.7% through increased de novo and mixed fatty acid production, and milk protein up from 3.0% to 3.5% in the same lactation, without negatively impacting milk yield.
While butterfat remains key to overall dairy income-over-feed-cost (IOFC), milk protein can be significant, too. It plays an outsize role in cheese manufacture, particularly in Northeastern markets.
One possibility, Van Amburgh notes, is that non-essential amino acids (NEAA) like proline might turn out to be a limiting factor for milk protein in high-producing cows at certain stages of lactation, which could affect the casein content of their milk.
Proline is the fourth most abundant AA in casein, and, under conditions of high nutrient demand, could become limiting for protein yield. Casein proteins make up 80% of the proteins in cow’s milk and are essential to cheese manufacture, where even a few points more milk protein may improve IOFC for the dairy producer.
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