Japan — Kuroge Washu wagyu breeding intensified from Meiji era when selective breeding began; Kobe beef brand established internationally through the 1950s export trade; Matsusaka and Omi designations developed in parallel
Wagyu (和牛, Japanese cattle) encompasses four breeds: Kuroge Washu (Japanese Black, comprising 95% of all wagyu production), Akaushi (Japanese Brown/Red), Nihon Tankaku (Japanese Shorthorn), and Mukaku Washu (Japanese Polled). The extraordinary intramuscular fat (IMF) marbling that defines premium wagyu is almost exclusively a Kuroge Washu characteristic. The Beef Marbling Score (BMS) is Japan's standardised marbling system: BMS 1–12, where BMS 3–4 represents standard Japanese supermarket beef, BMS 5–7 is premium (A4), and BMS 8–12 is the extreme marbling category (A5) that includes the most celebrated regional wagyu. The Japan Meat Grading Association evaluates BMS alongside yield grade (A/B/C) and three carcass quality factors to produce the final A5/B4/etc. designation.
A5 Kuroge Washu: exceptional sweet, buttery, rich fat that melts at body temperature, concentrating into an extraordinary savouriness; the fat is the flavour, not a vehicle for it
The intramuscular fat in wagyu is uniquely high in mono-unsaturated fatty acids (particularly oleic acid) compared to most other beef — this gives the fat a lower melting point, producing the 'melt in the mouth' sensation at body temperature and contributing a sweet, buttery character. The three most celebrated regional wagyu: Matsusaka ushi (Mie Prefecture) — bred from young virgin cows, extremely high marbling; Kobe beef (Tajima cattle from Hyogo, BMS 6+ minimum for certification); Omi beef (Shiga Prefecture, Japan's oldest documented wagyu brand). Each has strict certification rules about breed, feed, region, and age.
The highest expression of A5 wagyu is often simple shabu-shabu or teppanyaki — the fat's natural sweetness is best showcased with minimal seasoning (rock salt, wasabi, or the beef's own rendered fat). For a comparative tasting, try the same grade from Matsusaka, Kobe, and Omi beef side-by-side — the feed and region variations produce detectably different flavour profiles despite similar marbling scores. Use wagyu fat trimmings to cook accompanying vegetables — a piece of rendered wagyu fat in the pan transforms ordinary vegetables.
Treating A5 wagyu the same as ordinary steak — grilling thick cuts of A5 loses the extraordinary fat character; thinner cuts (3–5mm) on a teppan or very brief pan sear reveal the quality best. Not resting adequately before serving.
Japan Meat Grading Association documentation; Tsuji, Shizuo — Japanese Cooking: A Simple Art; Davidson, Alan — The Oxford Companion to Food