This year we decided to try ultrasound on some of the bulls in bull test. Most other breeds such as the Hereford, Angus, Shorthorn and Charlois have been using ultra sound for up to 5 years. We have always considered Murray Greys to be the best at marbling and passing along those genetics but other than our numerous carcass wins at various carcass competitions, we had no other source of carcass grading. When talking to the ultra sound technicians as well as some of the herford breeders there were several things that were impressed upon us.

1. The results are relative.

2. The results are genetic in that certain families will have higher marbling than others.

3. Heifers should be done at about 1 year of age. Age should be kept constant as it affects results and ones with low results can be culled from the herd.

4. Relative EPD's can be extrapolated from the results but must be done from the states. This involves some extra costs and the animal must have a strip shaved in it's side.

The accuracy of the ultrasound depends upon the technician doing the readings. Our results were done by Rod Wendorff and Doug Ralph both certified technicians. The accuracy is high enough that bulls selected based on ultrasound results will result in a positive genetic change in progeny carcass traits. Heritability for carcass traits are moderate to high, being slightly higher than birth weights, weaning weights, and yearling weights.

It is a well know fact that marbling is the best indicator of just how tasty the beef will be. Research shows that meat AAA and above produces the most satisfied consumers. As marbling increases so does the juiciness, flavor and the tenderness, so why not use all means available to better production from the ranch.

So to understand the ultra sound results.

Marbling

3.00 – 3.99…………..Single A……………..Standard

4.00 – 4.99…………..Double AA…….…….Select

Above 5.00………….Triple AAA…….…….Choice

Remember that the age of the animal should be taken into consideration. A high AA that will be fed for an additional 90-100 days will likely result in a AAA carcass. Keeping in mind that some genetics may never reach AAA.

Back Fat MM

The fat measurement gives an indication of the bulls fleshing ability. Fat bulls have less lean meat/muscle in the carcass. Calves from a bull with very little fat may finish too slowly. Bulls with excessive fat may suffer reduced fertility. Back fat is also related to a female's ability to produce milk, rebreed, reach early puberty and maintain a short calving interval.

Rib Eye Area (REA IN2)

The Rib Eye is the largest muscle in the body at birth so the REA gives an indication of overall carcass muscling. This is measured in inches. Big is good but read on…..

Adjusted REA IN2/100 lbs

The largest rib eye area may belong to the largest bull. Adjusting the REA to 100 lbs body weight helps determine which bulls are more muscular and which bulls are simply heavier.

Cutability (%LMY)

Cutability is the percentage lean meat yield in the carcass. Back fat will reduce yield by 7 to 8 times what REA will increase the yield.

So to sum it all up.

• It is desirable to have an animal that has high marbling, large rib eye and high percentage lean meat yield.

• Remember that moderation and balance are key ingredients of a successful breeding program.

• Knowing what cow families produce the best marbling will only increase your yield and herd performance.