Wagyu cattle have a predisposition for superior marbling, this is both in terms of the amount of marbling and the composition of marbling. Wagyu cattle’s trademark marbling has been proven to be a highly heritable trait. The Australian Wagyu Association’s collaborative genetic research project calculated the heritability of AUS-Meat marble score to be 52%. A 2011 Japanese study (Nogi et. al. 2011) found the heritability of Beef Marble Score (BMS) to be 51%. It is common for Wagyu and Wagyu cross cattle to have intramuscular fat (IMF) percentages from 20% to even 50%. Marbling is a key driving factor in the premium value Wagyu cattle and beef demand globally.

Marbling Scales

There are a variety of different marbling scales used globally, it is important to understand what scale is being used when reviewing data and buying or selling Wagyu beef. There are three major scales, the USDA marbling scale, the AUS-Meat marbling scale, and the Japanese Beef Marbling Score scale.

The USDA marbling scores consist of four different categories based on the level of marbling. They are from in order of quality from worst to best Standard, Select, Choice, and Prime. Prime is classified as having moderately abundant marbling (12% or greater). Only an estimated 9% of cattle in the USA graded Prime in 2019.

USDA Beef Grading Facts:

The Australian marbling scale is the AUS-Meat system, a 0 (least) – 9 (most) ranking based on the amount of marbling. The scale typically starts at 1 (1% IMF) and goes to 9 (21% IMF). Carcasses with IMF percentages exceeding 21% are given a further score of 9+. This scale exceeds the USDA scale but still stops where the Japanese BMS scale begins.

AUS-Meat Grading Facts:

The Japanese marbling scale is the Beef Marbling Score (BMS) system. This system was revised in 2008 and is a 1-12 scale with 1 being worst and 12 the best. Scores 1 and 2 are rare representing animals with little to no marbling. The scale typically begins at 3 (around 21% IMF) and goes to 12 (56% IMF and above). This system also takes into consideration marbling fineness and distribution.

Often confused with a marbling scale is the Japanese quality grade scale, which is based on yield and quality (Fat color, meat color, marbling, and texture). The highest quality grade is A5. To make the A5 grade the carcass must have a yield of 72% or above, a BMS of 8-12, meat color No. 3 – 5, fat color No. 1 – 4, and a very fine texture.

Japanese BMS Guide:

Japanese Quality Grade Guide:

Objective Measurement

Objective measurement is extremely important in the collecting of carcass data. The industry standard is utilizing a independent 3rd party certified grader or software analysis system. These graders and systems typically measure marbling, rib fat, ribeye muscle area, fat color, meat color, and more. Some of the popular systems used in the Wagyu industry include accredited AUS-Meat graders, a Meat Image Japan (MIJ) Carcass Camera, a MasterBeef Carcass Camera, and Meat & Livestock Australia (MLA) graders.

MIJ Camera Fact Sheet:

Master Beef Website:

AUS-Meat Website:

MLA Website:

Health Benefits

Wagyu beef has been shown to have higher Mono Unsaturated Fatty Acid (MUFA) content than conventional beef, have more Oleic Acid than conventional beef, and a higher ratio of Unsaturated Fatty Acid (UFA) to Saturated Fatty Acid (SFA) than conventional beef. To top it off, consuming beef high in MUFA has been shown to decrease the “bad” Low Density Lipoprotein (LDL) cholesterol and increase the “good” High Density Lipoprotein (HDL) cholesterol. Studies have proven Wagyu’s superior MUFA, Oleic Acid, overall Fatty Acid profile to be highly heritable. This means the probability of Wagyu passing on their superior traits to their progeny is high regardless of their environment.

The Mono Unsaturated Fatty Acid (MUFA) content of Wagyu beef has been measured at 59.9% of all Fatty Acids (Zembayashi et. al. 1995), 57.1% of all Fatty Acids (Gotoh et. al. 2016), and 56.4% of all Fatty Acids (Nogi et. al. 2011). These high figures in turn give Wagyu beef a high MUFA: SFA ratio that has been measured at 1.69 (Zembayashi et. al. 1995), 1.43 (Nogi et. al. 2011), and 1.37 (Gotoh et. al. 2016). Conventional beef regularly has a MUFA: SFA ratio of around 1.10. The heritability of MUFA in Wagyu has been measured at 68% (Nogi et. al. 2011).

Oleic acid is a key driving factor in the incredible taste, flavor, juiciness, and low melting point of Wagyu beef. Oleic acid is the monounsaturated omega-9 fatty acid found in olive oil. Oleic acid levels in Wagyu exceed that of regular beef, normally exceeding 50% of all fatty acids. Oleic Acid in Wagyu has been measured at 51.27% (Nogi et. al. 2011) compared to conventional beef at 45% of all fatty acids.

According to Dr. Stephen Smith, Oleic Acid decreased the levels of LDL cholesterol and increased the HDL cholesterol levels in Texas A & M studies. The American Heart Association reports high levels of HDL are associated with reduced risk for heart disease and heart attacks, whereas low levels of HDL (less than 40 mg/dL) are associated with increased risk of heart disease (Texas et. al. 2020).

The high reported levels and heritability of Wagyu’s marble score, MUFA, Oleic Acid, and MUFA: SFA gives significant weight to the strong health claims frequently attached to Wagyu beef. The Wagyu industry has the potential to select for and improve these traits due to their high heritability.



Gotoh, Takafumi, and Seon-Tea Joo. “Characteristics and Health Benefit of Highly Marbled Wagyu and Hanwoo Beef.” Korean Journal for Food Science of Animal Resources, Korean Society for Food Science of Animal Resources, 2016,

Hale, Dan. “USDA Beef Quality and Yield Grades.” Meat Science, 26 Oct. 2018,

Nogi, T. “Heritabilities and Genetic Correlations of Fatty Acid Compositions in Longissimus Muscle Lipid with Carcass Traits in Japanese Black Cattle.”, 2011,

Texas Wagyu Association. “Wagyu Beef.” Texas Wagyu Association, 2020,

Zembayashi, M. “Effect of Breed Type and Sex on the Fatty Acid Composition of Subcutaneous and Intramuscular Lipids of Finishing Steers and Heifers1.”, 1995,