Not all fat is created equal. When it comes to eating quality, there is one clear ruler. All hail intramuscular fat, also known as marbling. This is the small pockets of fat dispersed throughout the muscle in a steak. It improves meat flavour, aroma, juiciness, and tenderness. But being yummy isn’t a cattle beasts highest priority.

Intramuscular fat is the last fat to accumulate in growing cattle. So the general rule of thumb is that cattle need some chubby on the outside before they start marbling on the inside. No intramuscular fat until you’ve stacked something on your back. But can you have more marbling without overblowing it on external carcase fat?

The B+LNZ geneticists have been giving this relationship between rib fat depth and marbling a closer look. They have analysed the data from over 2,100 B+LNZ Beef Progeny Test cattle that have been assessed for both traits. And, yes, cattle with more subcutaneous fat on the outside tend to have higher marbling scores. But the genetic correlation is moderate. Rib fat depth EBVs only explain about 16% of the variation in marbling score. That is a good thing because it means that there is scope to identify bulls that have high-marbling scores without excessive rib fat depth.

Since the 1990s many breeders have been working hard to improve marbling in grass-fed beef. Some good gains have been made and there is plenty more room to marble it up further.