Marbling
Marbling is the intramuscular fat (IMF) within the muscle and between the muscle fibres which appears as fine flecks of fat within a muscle. Marbling is a key specification of carcase value in many of our high quality beef markets, particularly grain fed carcases for hospitality or export markets such as Japan. Marbling generally improves the eating quality of beef, particularly palatability traits such as juiciness and flavour.
Intramuscular fat is the last fat deposited in the animal so the finishing stages of an animal are most critical.
Genetics:
- Marbling is moderately heritable (30-50%) and can be improved through genetic selection.
- Estimated breeding values (EBVs) for IMF% can be used to assist with selection.
On-farm and feedlot management effects to increase marbling include:
- Reduce stress through good temperament and management as this may adversely affect marbling.
- Castrate early, creep feed, low stress wean, and vaccinate to reduce the likelihood of sickness.
- Limit the use of hormone growth promotants (HGPs) which may reduce marbling.
Nutritional effects on marbling:
- To maximise marbling, cattle must be on a high nutritional plane and be well finished.
- The level of marbling is greater in grain finished cattle due to high energy rations, compared to animals fed lower energy pasture diets.
- Faster backgrounding growth rates (especially 10-14 months) will enhance marbling in the carcase after feedlot finishing.
- Backgrounded at 0.8kg/day or better will best suit a long-fed export target market.
- The higher the energy in the diet, the more likely an animal will express marbling.
- Growth restrictions earlier in life as a result of feed restriction, drought, or illness will reduce marbling.
Generally, marbling is graded on a subjective visual basis, assessed and scored against marbling reference standards. Marbling is assessed on the eye muscle (M. longissumus dorsi) or at the quartering site (usually between the 10th and 11th ribs or 12th and 13thribs).
The AUS-MEAT marbling scores range from 0 (nil) to 9 (abundant) and are assessed based upon the amount of marbling present in the eye muscle.
MSA marbling scores are used to provide a finer scale than the AUS-MEAT scores. It is assessed based upon amount as well as distribution of the marbling within the eye muscle. Each MSA marbling score is divided into tenths for grading, creating a score range from 100 to 1,190 in increments of 10.
MSA and AUS-MEAT marbling scores are determined independently, as the assessment criteria are different.