Understanding 305‑AA: A New Standardized Yield Metric Now Available in VAS Tools
The CDCB’s new standardized milk yield metric known as 305‑AA will now be displayed in DairyComp and VAS PULSE Platform alongside familiar 305‑ME values.
This update reflects an industry‑wide move to evolve how milk, fat and protein yields are standardized based on today’s cows, management practices and environments.
Why the industry introduced 305‑AA
For decades, standardized production values were calculated using 305‑ME (Mature Equivalent) adjustments. Those adjustment factors were developed in the early 1990s before today’s genetics, housing, nutrition and management practices became widely adopted.
Recent research conducted by the Council on Dairy Cattle Breeding (CDCB) and USDA, and published in the Journal of Dairy Science, showed that cow maturity patterns and environmental effects have changed significantly over the last 30 years. As a result, older mature equivalent assumptions tended to overestimate yields compared to what modern cows actually produce.
To address this, the industry introduced 305‑AA (305‑Average Age), which standardizes production to a cow at 36 months of age rather than to a mature equivalent benchmark. This change supports more accurate comparisons across cows of different ages, breeds and climates – using data that better reflects today’s dairy herds.
How 305‑AA is calculated
At a high level, 305‑AA uses the same underlying projected production values producers are already familiar with, but applies updated adjustment factors. Similarly to 305-ME, 305-AA accounts for a 2X milking frequency and uses the same methodology to determine days open.
The key change is the AA (Average Age) factor, which replaces the older mature equivalent factor:
Calculated each lactation on an individual cow basis
Based on updated industry research around age, breed, seasonality and regionality
Applied to projected 305 milk, fat and protein values
Because projected 305 values are updated with each test day, 305‑AA values are also refreshed each test day, ensuring the metric reflects the most current information available.
In both DairyComp and PULSE, the calculation is:
305‑AA = AA factor × projected 305 yield
What you’ll see in PULSE and DairyComp
VAS is displaying the new 305-AA metrics alongside traditional 305-ME values to give you a side-by-side view. 305-AA will not be used in any calculations including CowVAL and RELV at this time.
In PULSE, users will see:
- 305‑AA (milk)
- 305‑AA fat and 305‑AA protein
- AA adjustment factors for milk, fat and protein
- AA305, which is based on daily milkings (while 305‑AA updates on each new test day)
In DairyComp, users will see:
- 305AA (305‑AA)
- AA305
- AAFAC (AA adjustment factor)
Why this matters
305‑AA is based on analysis of more than 100 million lactation records, using updated data that reflects modern genetics, climate conditions and management practices.
Want to learn more?
If you have questions about how 305‑AA is calculated, we encourage you to reach out to your VAS farm performance consultant or support team.
This update reflects industry research led by the Council on Dairy Cattle Breeding (CDCB) and USDA scientists, including:
- Miles, A., VanRaden, P., Hutchison, J., et al. Introducing 305‑AA: The New National Standardized Yield Measurement. Journal of Dairy Science.
https://www.journalofdairyscience.org/article/S0022-0302(25)00679-4/fulltext - CDCB. Introducing 305‑AA: The New Standardized Yield Measurement.
https://uscdcb.com/introducing-305-aa-the-new-standardized-yield-measurement/