Texas A&M Ultrasound Certification Workshop
Like many youth, I showed market lambs as my 4H and FFA projects. We raised most of the lambs that we showed and bought a few, mostly breeds that we did not raise. My older siblings paved the way, which allowed for me to be fairly successful. This experience developed a passion for the sheep industry that sticks with me today.
My parents own a small meat packing plant, so I had the good fortune of seeing carcasses on a regular basis. Naturally, we selected lambs based on their cutability or amount of lean cuts that we predicted a live animal would yield on the rail, with an emphasis on high-value cuts.
During the 1990s, the time that I showed lambs, there was a trend for long, tall, and lean lambs. We always joked “You can’t eat the air underneath them!” or “Hard as rock! Who wants to eat a rock?” Times have definitely changed because winning show lambs are much different than they were 20 years ago.
When we visually look at a lamb and handle them, we can estimate how fat they are and how muscular they are. But it is only an estimation and often we may disagree which lamb has more muscle. Trust me, my family rarely agreed on which lamb was better! But for a commercial operation in the business of selling meat, it is much better to have a definitive way to quantify this.
Ultrasonography is a fairly powerful tool that can help address this topic. But first we must determine what we want to measure.
The most valuable parts of a lamb carcass are the rack and loin. Combined these two primals represent almost half the value of the entire lamb carcass. And one muscle makes up most of the lean meat in both of these primal cuts, the longissimus dorsi. For the purpose of this article, I’ll refer to it as the loin muscle. Obviously, increasing the size of the loin muscle can have a major impact on the value of a lamb carcass.
Ultrasound can accurately predict loin area and depth of a live lamb. Most often, this is measured between the 12th and 13th at the junction between the rack and loin on a lamb. This measurement should be taken on a lamb around the time the lamb would normally go to market. However, most of the time, we are testing breeding animals not going to slaughter but instead are retained for breeding purposes.
Ultrasound can also accurately predict the amount of fat that has accumulated over the loin eye muscle. The amount of fat at this location is used to predict the amount of fat that will need to be trimmed off the carcass. Some fat is needed to ensure the animal will result in high quality lamb but too much fat is unwanted. Fat deposition on a lamb is primarily influenced by diet; however, some lambs put on fat sooner than others. Both loin muscle depth and back fat depth are moderate to highly heritable traits. Therefore, selection can have a fairly rapid impact on future generations.
Sheep ranchers who wish to increase the value of the lamb carcasses they produce should buy or retain rams that have larger than average loin muscles. Or at least cull rams in the bottom 25 percent of their contemporary group. And if they wish to raise lambs to larger weights prior to slaughter without becoming too fat, they should select for breeding animals that are leaner than other. But fat deposition is positively correlated with reproduction; therefore, overly lean animals can have a negative impact on the lamb crop.
In April, we hosted a workshop that trained nine technicians to collect loin muscle area, loin muscle depth, and fat depth via ultrasound. This workshop was hosted at the Texas A&M AgriLife Research and Extension Center in San Angelo. Christopher Schauer, director of North Dakota State University’s Hettinger Research and Extension Center, was the lead instructor. He is the ultrasound committee chairman for the National Sheep Improvement Program. This workshop was partially funded by a grant through the National Sheep Industry Improvement Center.
Participants were trained on how to properly collect this data on day 1 and tested on their ability to accurately collect the data on day 2. Participants have standards that they must pass to be certified to collect data for the National Sheep Improvement Program. A list of certified technicians is available at http://nsip.org.
To best use the data, breeders should submit loin and fat depth measurements into the National Sheep Improvement Program, which converts the raw data into estimated breeding values (EBVs). These EBVs account for non-genetic factors that influence loin and fat depth measurement. Therefore, they are much more reliable than raw data. For instance, 80 percent of loin muscle depth can be predicted based on animal body weight. Therefore, loin muscle depth must be adjusted for live body weight to accurately predict carcass cutability.
To provide feedback on this article or request topics for future articles, contact me at reid.redden@ag.tamu.edu or 325-653-4576. For general questions about sheep and goats contact your local county Texas A&M AgriLife Extension office. If they can’t answer your question, they have access to someone who can.