Fat - rib fat thickness and distribution
Rib fat
Rib fat thickness is the measured depth of subcutaneous fat over the quartered rib site between the 5th and 13th ribs. Rib fat thickness may vary between sites and typically increases towards the head (5th rib). Rib fat is a better indicator of yield than the P8 site. It is measured when the carcase is chilled and quartered, as opposed to P8 fat being measured on the hot carcase on the slaughter floor.
An adequate covering of fat is needed to protect the carcase from rapid chilling, which can cause toughening, and to enhance eating quality and appearance. MSA has a minimum requirement of at least 3mm of rib fat. Each market specifies an optimum fat depth that suits their customer requirements.
Fat distribution
Fat distribution is important for both yield and quality. The key requirement for all beef markets is to have adequate cover over the high-value cuts along the loin (back) and rump.
Fat distribution is affected by the genetics and nutrition of the animal. Higher boning yield results from moderate to heavy muscled animals grown consistently to produce adequate and even carcase fat.
MSA requires carcases to have adequate fat coverage over all major primals. An area of inadequate fat distribution greater than 10cm x 10cm will result in an ungraded carcase.
These cattle did not grow fast enough during the finishing period to put on the required amount of fat.
If you bought them to finish for this market, the cattle were probably too lean or had too much European content to finish at this weight.
If you bred these leaner cattle:
- The simplest option next time would be to carry them on to finish for a heavier market, or sell them as feeder cattle.
- To do a better job of hitting this target market, give them better nutrition earlier in their life, with better quality pastures or supplements. This would allow them to reach the target weight earlier (at a younger age) and put on more fat.
It would also be possible to consider changing the genetics of the cattle so they are easier to finish at this weight, but this may reduce their potential growth rate and value as feeder cattle.
You can use the BeefSpecs tool to see how the weight and fat specifications of your cattle change as they grow. This can help you decide which market to target and predict when the cattle will be ready.
These cattle may have been suited to a lighter weight market, before they became too fat.
They would not be suitable to target markets heavier than this unless they were grown out slowly first to develop a bigger frame and more muscle.
If you bought them to finish for this market, they were probably too small in the frame, lightly muscled, or had too much fat on them at the start.
If you bred them, there are three main options:
- Consider targeting a lighter weight market and sell them earlier, when they are finished.
- Increase the stocking rate, this may slow their individual growth and reduce fatness while increasing beef produced per hectare.
- Use genetics to increase their frame size and/or muscling so they are not as fat at this weight.
The genetic option can be done by bull selection using carcase EBVs within your breed, or by crossbreeding. This option requires careful planning - don't add too much frame size or you may affect breeding efficiency, or need to make other changes.
You can use the BeefSpecs tool to see how the weight and fat specifications of your cattle change as they grow. This can help you decide which market to target and predict when the cattle will be ready.
Rib Fat Key Points
- Fat distribution is the coverage and distribution of subcutaneous fat on a carcase.
- Carcases may fail to meet MSA specifications if the fat distribution is inadequate because even fat distribution is required to ensure the carcase chills at a uniform rate.
- It is important that cattle have access to an increasing plane of nutrition for at least one month prior to slaughter to assist in even fat coverage.