Q: What were some of the highlights of the Cornell/Miner Institute Advanced Dairy Nutrition Shortcourse?
A: The course had considerable focus centered around the science and modeling of amino acids, fatty acids and fiber digestion. Transition cows were touched on in many of the discussions, and attendees were given a tour of the recently opened Cornell Dairy Research Center.
Q: What were topics that really stood out on modeling dairy rations?
A: Advancements in nutritional modeling continue to allow the nutritionist to formulate rations for higher levels of production and greater efficiency. Improvement to the Cornell Net Carbohydrate and Protein System (CNCPS) model was one of the many topics covered. Several sessions focused on the predictability of metabolizable protein (MP) and amino acid (AA) flow by CNCPS, and rethinking the way we express amino acid requirements.
Q: Tell us more: What’s new with MP and AA?
A: An article published several years ago in the Journal of Dairy Science showed that several commercial models predict essential amino acid flows with reasonable accuracy, and planned updates to CNCPS will further remove hurdles to adoption of essential amino acid (EAA) balancing in diets for dairy cows. One such improvement is updating the amino acid composition of feed ingredients, which is critical to the accuracy of prediction of MP from rumen undegradable protein (RUP), since one-half of the MP from today’s rations is derived from RUP.
If you want to check the accuracy or update the amino composition of feed ingredients in your library, NRC 2001 is a good place to start. The forthcoming amino acid updates to CNCPS’s feed library indicate that methionine is currently too low for most ingredients, and other EAA are a mixed bag of too high or too low.
In addition to changes on the AA supply side, changes to AA requirements were discussed. Efficiency of AA use is overestimated in the current model for most AA with Met and Lys at 97% and 82%, respectively. Future updates to CNCPS will have efficiencies for these two AA in the range of 66-69%, which is a considerable decrease. This will result in CNCPS’s amino acid requirements being more in-line with other nutrition models.
Q: What affect will these changes have on ration formulation?
A: The changes result in benchmarks changing slightly when the library is updated. Currently, to maximize milk protein yield the recommendation for methionine as a percentage of MP (MP-Met %) is 2.35 and lysine (MP-Lys %) is 6.93%. Suggested targets after update increase to 2.5% MP-Met and 7.0% MP-Lys.