Wagyu is renowned for its marbling in the form of intramuscular fat (IMF) which appears as fine flecks within the muscle. The presence of marbling has a very positive effect on the eating quality of beef in terms of tenderness, juiciness and flavour, giving Wagyu an exceptional eating experience.
The marbling score is a component of the AUS-MEAT beef quality grading system, and refers to visible fat found between muscle fibre bundles and is assessed within the rib eye muscle. Marbling score is assessed visually by an AUS-MEAT qualified grader during the process of carcass grading using the scoring range 0 to 9 as shown below. The distribution and texture of the fat flecks, referred to as fineness are also assessed.
To give a more precise result, intramuscular fat may be measured by chemical extraction of lipids from a thin facing of the exposed rib eye muscle. Therefore, the percentage of intramuscular fat is an objective measurement that quantifies the total fat content within the rib eye muscle. Camera technology developed by Meat Image Japan specifically for Wagyu can also be used to quantify Wagyu marbling and is used by the AWA for Australian Wagyu.
Wagyu cattle that are Fullbloods have the highest level of marbling of any beef breed. Through its higher marbling, Wagyu beef possesses a higher proportion of monounsaturated fat, compared to other beef. According to Tim Crowe, Ph.D., senior lecturer of nutrition at the School of Exercise and Nutrition Sciences at Deakin University in Australia, the monounsaturated fatty acid to saturated fatty acid ratio runs up to three times higher in Wagyu beef than other beef. Crowe says half of all marbling in Wagyu is comprised of monounsaturated fats. Wagyu beef can therefore be eat in place of other breeds within the recommendations of overall red meat intake as part of a healthy and balanced diet.
Marbling potential is determined by both genetics and nutrition. To attain the highest level of marbling, Wagyu is fed on a diet of straw for roughage and grain for protein and carbohydrates. While Wagyu will develop considerable marbling from quality grass feeding, most are feedlot fed on carefully designed rations of straw for roughage and grain for protein and carbohydrates.
In Australia Wagyu Fullbloods are fed for 400 – 650 days with the aim of producing marble score at least 8+, achieving carcase weights of 300 – 450 kgs.
Crossbred Wagyu are fed for 350 – 450 days with the objective of producing marble score 5 – 7+, achieving similar carcase weights as Fullbloods but with much greater marbling variability.
Estimated Breeding Values for IMF (intramuscular fat) may be used to select Wagyu Fullblood and Purebred males and females to improve marbling levels. Refer to our news item on discovering Wagyu’s best marbling genetics.