Bluebonnet Livestock Services

figure 1. Carcass Data collection using real-time ultrasound

The beef industry has experienced major changes since the beginning of 1990. Reproductive techniques, genetics, nutrition, and management have helped producers become more efficient in their best management practices (BMPs). The industry also has seen the coming together of strategic associations and, to a certain degree, value-based marketing. Source verification is suggested as a way of tracking individual animal performance through the production chain. With all of this in mind, what can a producer do to be in a workable position for the future market?

In a value-based marketing system, viability of the beef industry depends on the ability of individual producers to provide a high-quality, consistent end product. One of the industry's newest technologies, real-time live animal carcass ultrasound, offers beef producers a reasonable way to make genetic improvement in carcass traits (Figure 1).

Until recently, the only way to collect carcass data on sires was to evaluate steer progeny through the feedlot and packing plant; collection was a slow, laborious, and expensive task. It required seed-stock producers' retaining ownership of some of their calves through the feedlot or arranging for carcass data to be collected on bull-customer's calves. The collection of actual carcass data on steer progeny was time-consuming and costly. The average time period to "prove" a sire for carcass merit was 2 to 4 years, at a cost of $3,000 to $5,000. Because of these constraints, relatively few bulls have accurate, meaningful carcass data collected. Without these data, seed-stock producers cannot make sound selection and culling decisions, and commercial producers cannot purchase sires to produce calves for the value-based market. This is where carcass ultrasound can play a valuable role.

The beef industry needs to develop a substantial database for the generation of breeding values for carcass traits. The quickest, least expensive method of establishing this database is to obtain accurate and precise live-animal measures of body composition. The use of real-time ultrasound provides a noninvasive method for estimating the economically important carcass traits on live animals. By using ultrasound technology to collect carcass data on live animals, progeny testing can be completed in less than 2 years for about $450 per sire.

The most economically important carcass traits include ribeye area (REA), back fat (BF), intramuscular fat (IMF) or marbling, and rump fat (RF). Each of these carcass traits can be accurately and precisely measured in the live animal with the use of ultrasound. Carcass traits are moderately to highly heritable (most range from 30 to 60 percent), which shows that selection for improved carcass quality and consistency should be beneficial. If producers can use carcass ultrasound to determine carcass traits in the live animal, they can make informed selection and culling decisions.

Ribeye area and back fat thickness are two traits highly related to retail production of a beef carcass. Fat thickness and percent retail product are inversely related; the higher the fat thickness, the lower the percent retail product. The ribeye area is positively correlated with pounds of retail product. These two traits, in addition to hot carcass weight, are used in the USDA Yield Grade formula that predicts "cut ability," or percentage retail product. Fat thickness accounts for the majority of variation found in beef- carcass-yield grades. Within a specific carcass-weight range, however, the ribeye area may have a significant impact. You can use ultrasound to measure these traits with a high degree of accuracy.

Beef producers can objectively measure marbling in live cattle using real-time ultrasound; it is reported as percent fat in the ribeye muscle. Percent fat correlates with a USDA grader's subjective visual evaluation of marbling in a beef carcass. Percent fat is the primary component for determining carcass quality.

Ribeye area represents a cross-sectional area of the ribeye muscle at a point between the 12th and 13th ribs (Figure 2). This area is the most commonly used indicator of total carcass muscle and is used in yield grade calculation. Ultrasound measurements of the ribeye area are accurate and closely identified with the actual carcass ribeye area.

Back fat thickness represents the under-the-skin fat thickness between the 12th and 13th ribs over the longest back muscle (Figure 2). This is the most common measure of extramuscular fat on a carcass. Back fat thickness is directly related to carcass yield grade. The greater the back fat thickness, the higher the yield grade (yield grade ranges from one to five, with one being the highest yielding animal and five the lowest yielding, or least desirable). Back fat thickness is the most accurate of the carcass ultrasound measurements and is highly connected to the actual carcass back fat.

Intramuscular fat (marbling) represents fat deposited within the muscle. Intramuscular fat (IMF) is measured in a longitudinal image of the long back muscle taken over the 11th, 12th, and 13th ribs (Figure 3). The ultrasound measurement actually estimates the percentage intramuscular fat that is highly correlated to the degree of marbling in the carcass (Figure 4).

Degree of marbling is one of the principal factors in determining USDA quality grades in slaughter cattle. Animals that have less than 2.58 percent intramuscular fat get grade USDA Standard, those with 2.58 to 3.90 percent intramuscular fat are graded USDA Select, and animals with 3.90 to 8.55 percent qualify for the USDA Choice grade. Animals with more than 8.55 percent marbling are given grade USDA Prime (Table 1).

Figure 5. Ultrasound image of rump fat.

Rump fat measurements are taken over the rump between the hooks and the pins (Figure 5). Rump fat is negatively associated with the percent retail product and is an additional indicator of total carcass fat. The greater the rump fat, therefore, the lower the percent retail product. Rump fat measures may be most useful for predicting percent retail product in leaner cattle that have less 12th-rib fat.

Several breed associations are actively developing carcass EPDs based on live animal carcass ultrasound measurements. Producers can get these measurements on yearling bulls and heifers (320 to 440 days of age) to develop EPDs to predict carcass differences in their progenies. Individual animal weights must also be taken within 7 days of collecting the carcass images. As noted, this is faster than collecting carcass data in the packinghouse.

In the collection of scan data, it is important seed-stock producers collect ultrasound carcass data from animals within contemporary groups, which include animals of about the same age, same sex, same season of birth, and raised under similar management conditions. Producers need to collect carcass ultrasound data from animals in the yearling age category (320 to 440 days of age). Also, live animals' weights should be taken within 7 days of collection of carcass ultrasound data. It is important to note scan data can be different from animals of different sexes and under different nutritional regimes. Com-pare only animals within contemporary groups and under similar management. Scan data is most useful in identifying sires or bloodlines that are superior or inferior for a particular trait of interest.

Commercial beef producers can use carcass ultrasound data to help select the proper herd sire. Using a combination of breed association carcass trait EPDs, along with actual carcass ultrasound data, can greatly help commercial producers select herd sires with potential to produce calves for retained ownership. More commercial producers are choosing to retain ownership through the feedlot, which allows them to take advantage of superior genetics within their own herds. Carcass ultrasound data can help ensure genetically superior calves are produced.

Many seed-stock producers are using this ultrasound to make critical selection decisions. The development of ultrasound-based carcass EPDs has the potential to greatly impact the beef industry. Sires could be proven for carcass traits more rapidly and less expensively, thereby effectively shortening the generation interval. These data would also benefit the commercial producer, allowing for the selection of specification sires to produce progeny destined for the feed yard and the consumer's plate.

By Allen R. Williams, Ph.D., Extension Animal Scientist, Animal and Dairy Sciences Department.

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This document is courtesy of Mississippi State University Extension Service.