Editors’ note: This article summarizes key takeaways from the peer-reviewed study “Relating the Canadian and Japanese beef grading sites.” It is an interpretive overview for Canadian readers; please consult the full paper for methods, statistics, and figures. [Read the full study →] 

Mapping Canadian Grades to Japan’s JMGA: What the New Research Means for Canada

Canada’s second-largest beef market is Japan. Yet converting Canadian grades into Japan Meat Grading Association (JMGA) grades has always been tricky because the two systems assess different rib sites and use different yield formulas. New research from AAFC-Lacombe and partners provides the most practical conversion guidance to date—especially for high-marbling carcasses destined for Japan.

Why the systems disagree

• Quality (marbling) site:

  • Canada: Marbling is scored on the longissimus thoracis (LT) at the 12th–13th rib using USDA pictorial standards.

  • Japan (JMGA): Marbling is scored at the 6th–7th rib using BMS 1–12 (and colour is formally considered).

• Yield approach:

  • Canada: assigns Retail Cut Yield (RCY) classes 1–5 using a ruler-based equation from the 12th–13th rib.

  • Japan: assigns A/B/C yield using an equation at the 6th–7th rib (inputs include LT area, rib thickness, carcass weight, fat thickness).

The study also confirms what many graders see on the rail: intramuscular fat (IMF) and colour vary along the LT and across nearby muscles, with the Japanese site generally showing higher IMF than the Canadian site. That anatomical difference alone can shift a carcass up or down when you translate grades.

The big translation wins (quality)

For the population studied (mostly high-end Canada AAA and Prime), the authors found practical, repeatable relationships:

• High Canada AAA (USDA Modest/Moderate) → typically high JMGA 3 to low JMGA 4.

• Canada Prime (USDA Slightly/Moderately Abundant) → typically high JMGA 4 to low JMGA 5.

What that means: Canadian plants can pre-sort for Japan using domestic grades and expect the bulk of AAA/Prime carcasses to land between JMGA 3 and low JMGA 5 on marbling.

Technical note: Statistical relationships for marbling were moderate (e.g., R² ≈ 0.33 at the carcass level). Translation: good guidance for sorting/pooling, but not a one-to-one predictor for individual carcasses.

Yield translation (where most questions arise)

Despite different formulas and rib sites, yield classes translate with useful patterns:

• Canada RCY 1 → JMGA A most often (~67%) and B for the remainder.

• Canada RCY 2 & 3 → largely JMGA B.

• Canada RCY 4 → mix of JMGA B (63.5%) and JMGA C (36.5%).

• Canada RCY 5 → B/C split; data were inconclusive.

Technical note: Multivariable equations using Canadian measures (CCW, REA, grade fat, marbling) explained up to ~56% of the variation in Japanese estimated yield. Single inputs explained less (e.g., carcass weight alone ≈ 9%).

Why this helps Canada

1. Feasibility: Packers can segregate AAA/Prime lots likely to hit JMGA 3–5, streamlining programs with Japanese customers.

2. Contracts & specs: Export programs can set evidence-based specs (e.g., “High Canada AAA for JMGA 3–4; Prime for JMGA 4–5”).

3. Risk management: Expect moderate prediction error; manage it by selling in lots/pools rather than promising an exact JMGA grade on every carcass.

4. Data feedback: Recording both Canadian rib-12/13 traits and Japanese rib-6/7 traits on trial lots will tighten plant-specific prediction over time.

Practical tips for graders & marketers

• Build a sorting matrix. Start with:

  • High AAA → target JMGA 3–4 programs.

  • Prime → target JMGA 4–5 programs.

• Layer in yield:

  • RCY 1 → prioritize A/B programs.

  • RCY 2–3 → steer to B programs.

  • RCY 4–5 → expect B/C; price accordingly.

• Mind the site difference. Higher IMF at the 6–7 rib can lift a JMGA call versus the 12–13 rib view.

• Colour counts in Japan. Manage chilling and bloom consistently; colour (L*, a*, b*) varied by muscle and site in the study.

• Pilot and calibrate. Run periodic side-by-side verifications on shipped lots to refine your plant’s conversion assumptions.

Read the fine print

• The dataset skewed toward upper marbling (mostly AAA, some Prime) and steers from common Canadian beef genetics; heifers and other breed types may track differently.

• Relationships are population-level, not guarantees for any single carcass.

• The JMGA yield model was developed on Dairy × Japanese Black crosses; beef-breed carcasses common in North America may be under- or over-estimated by that equation.