Wagyu Grades: What MB4+ and MB9+ Mean

Two lines sit next to each other on our menu at 29 Hamilton Road:

ANGUS PURE SOUTHERN AUSTRALIAN RIBEYE MB4+ — 300g grain-finished, truffle ponzu jus, salad

BLACKMORE FULL BLOOD WAGYU KARUBI MB9+ — 200g full blood wagyu short ribs, 600-day grain-fed, truffle ponzu jus, salad

Most people read those and conclude they’re looking at cheap wagyu and expensive wagyu. They aren’t. One of those two cuts isn’t wagyu at all — and the fact that both still carry an MB number is the single most useful thing to understand about Australian beef labelling.

MB is not a wagyu grade

MB stands for marble score, and it comes from the AUS-MEAT chiller assessment language: the standard vocabulary used to describe Australian beef carcases. It applies to any carcase that gets assessed. Angus, wagyu, a crossbred of the two — all of them can carry a marble score, because the score is describing the meat, not the animal’s pedigree.

So “MB9+” tells you something about a specific piece of beef. It tells you nothing whatsoever about breed. Our ribeye is Angus at MB4+; our karubi is full blood wagyu at MB9+; and if you only read the numbers you would never know the second sentence.

What the number actually measures

Meat & Livestock Australia sets it out plainly: the AUS-MEAT marbling scores run from 0 (nil) to 9 (abundant), and they are determined by the amount of marbling present in the eye muscle.

Three details in that sentence do real work.

It is scored in one place

Assessment happens at the eye muscle — the longissimus dorsi — at the quartering site, usually between the 10th and 11th ribs or the 12th and 13th. One cross-section of one muscle stands in for the whole animal. That is a reasonable proxy and it is still a proxy: a high score does not guarantee the same marbling in every cut off that carcase.

It counts amount, not arrangement

AUS-MEAT marbling scores the quantity of intramuscular fat. It does not score how finely or evenly that fat is distributed. There is a second Australian system that does — MSA marbling, which runs on a much finer scale from 100 upward and is assessed on amount and distribution. The two are determined independently, because the criteria are different. A steak can look very different from another steak carrying the same MB number, and both labels are telling the truth.

It says nothing about flavour

This is the part the marketing quietly omits. Marbling is measured; taste is not. Fat carries aroma compounds and it changes texture, so more of it does change the eating — but a number that counts fat in one cross-section is not a rating of how good the beef is, and it was never designed to be.

What the plus sign means

The “+” is a floor, not a flourish. MB4+ means marble score 4 or better. It is a guaranteed minimum: the kitchen is promising you at least a 4, and the piece on your plate may well be a 5.

At the top of the range, the plus does something more interesting. The AUS-MEAT scale stops at 9, but cattle don’t. Blackmore — the Victorian producer behind our karubi — puts it in as many words on their own site: where grading exceeds 9, it is considered a 9+. So 9+ is an open-ended top. Every animal from a 9 to something well past it lands in the same bucket, because the ruler ran out.

Which is worth knowing before you pay a premium for the difference between two 9+ labels. There may not be one. There may be a large one. The number cannot tell you.

Full blood, crossbred, and the word that matters

Here is where breed comes back in, and where the label genuinely earns attention.

Most beef sold as “wagyu” in Australia is crossbred — wagyu genetics bred into another breed, very often Angus. That is legitimate, it is widespread, and it produces good beef. It is also not the same animal as a full blood.

Blackmore’s own description of their herd is “100% Fullblood Wagyu beef, cattle that are not diluted with any other breed”, raised in the Victorian high country at Alexandra. Their finishing program runs 600 or more days on feed after an initial post-weaning ration — which is exactly the number printed on our menu line, 600-day grain-fed. That is not a marketing flourish we added; it is the producer’s program, quoted.

So the informative words on that menu line are not “MB9+”. They are “full blood“. Anyone can put a number on a card. “Full blood” is a claim about the animal that a supplier has to stand behind.

What the difference does on a plate

Now the useful part, which is not about scores at all but about portions.

Look again at the two menu lines and notice the weights. The Angus ribeye at MB4+ is 300g. The full blood karubi at MB9+ is 200g. That gap is not an accident of pricing. It is a cooking decision.

At MB4 there is enough intramuscular fat to keep a ribeye basting itself while it cooks and enough muscle left to eat like a steak. Three hundred grams of that is a portion one person finishes and enjoys finishing.

At MB9+ the ratio has flipped. There is so much fat rendering through the meat that richness arrives long before hunger leaves. Two hundred grams of short rib at that marbling is not a smaller version of the steak — it is a different eating problem, and the honest answer to it is to share. This is small-plate maths, the same logic that governs the rest of our table.

Short ribs deepen this further. Karubi is a hard-working cut off the rib plate, so it brings connective tissue and a beefier flavour that the very high marbling would otherwise flatten out. Pair extreme marbling with a lazy muscle and you get something that reads as rich and not much else.

Why there’s acid on both of them

One more thing our own menu quietly tells you: both cuts arrive with truffle ponzu jus. Ponzu is citrus and soy. That is a kitchen’s standard answer to fat — acidity resets the palate between bites so the tenth mouthful still tastes like the first.

It is also why marbling numbers should be read as a description of a problem to be solved rather than a score to be maxed out. The better the marbling, the more the plate has to work against it. A very high MB steak with nothing sharp beside it is a shorter meal than you were hoping for.

How to actually use the number when ordering

Three questions do almost all the work.

How much of it am I going to eat? Higher marbling isn’t better, it’s richer. Pick the score to match the portion and the appetite, not the occasion.

Full blood or crossbred? If the menu says wagyu and doesn’t say which, that is a fair thing to ask. Nobody minds.

What else is on the table? A 200g MB9+ short rib among mezze, pickles and something charred is a highlight. The same 200g alone is a rich plate with nowhere to go.

Japan grades beef by a different system entirely — the A5 letter-and-number labels come from a separate scale that measures marbling on twelve steps rather than nine, along with things AUS-MEAT handles separately. Comparing the two properly needs its own post, and forcing it into this one would only muddle the Australian scale we just untangled.

Both of ours, and where to find them

The Angus MB4+ ribeye and the Blackmore full blood MB9+ karubi are both on the Biggies section of the Hamilton Road menu, alongside the Mangalica pork collar chop and the charcoal chicken. Our food menu prints no prices — we explain how a bill here actually adds up in what dinner at Habibi-san costs — and if you’d rather the kitchen decided, there’s the chef’s-choice menu.

If you’re deciding where else in town beef is worth the money, we checked the field first-hand in wagyu in Singapore. For the wider picture there’s our guide to Japanese food in Singapore, the dish-led shortlist of the best plates in town, and a note on what to order at a fusion table if the whole menu is unfamiliar. Skewered beef is a different argument again, and it lives in our guide to skewers and charcoal.

Everything above is grilled over charcoal in an open kitchen you can see from the room — the gallery shows it. We’re at 29 Hamilton Road, Tuesday to Sunday, 5pm to 11pm. Book a table.