The_Ledger_Winter_2020

Impact of Production Scheme and Frame Size on Carcass Traits BY ROB MADDOCK, PH.D., ASSOCIATE PROFESSOR, DEPARTMENT OF ANIMAL SCIENCES, NORTH DAKOTA STATE UNIVERSITY C arcass traits help define the primary end product of beef production and are the primary driver in value differ On the heavy end, carcasses weigh ing more than 1,000 pounds were discounted $7 per hundredweight, and those weighing more than 1,050 pounds were discounted at $17 per hundredweight. The market does a good job of cattle will generally have desirable yield grades, but lower quality grades. Differences in genetic types can be explained by describing the rate of “maturity” of the cattle. “Early” matur ing cattle have a growth curve where the skeleton and muscle slows or

ences. After slaughter and chilling in a commercial packing plant, carcasses are presented to a U.S. Department of Agriculture (USDA) Agricultural Market ing Service grader for the assignment of USDA Quality Grade, Yield Grade and potential certification for a value added program. There are large value differences among carcasses depend ing upon grade, which can be seen by looking at current market reports. Market reports are available to the public and can be found at https:// www.ams.usda.gov. For example, in December 2019, the value of USDA Prime carcasses was approximately $14 per hun dredweight higher than Choice, and Choice was more than $21 per hun dredweight higher than Select. Yield Grade (YG) 1 carcasses (the trimmest and heaviest muscled) had a value of approximately $4 per hundredweight over YG 3, and YG 5 carcasses (the fattest and lightest muscled) were discounted $17 per hundredweight compared to YG 3. The other common discounts ap plied are for hot carcass weights. In December 2019, very lightweight carcasses of less than 500 pounds were discounted more than $30 per hundredweight, and carcasses with weights less than 600 pounds were discounted $12 per hundredweight.

indicating what grades and size of carcasses are most desirable to pack ers and ultimately consumers. Based on December’s market, carcasses In fact, the small-framed steers produced what is essentially the ideal carcass in terms of premiums and discounts. that weigh at least 600 pounds but less than 1,000 pounds, grade USDA Choice or better, and are YG 1, 2 or 3 would be the most ideal. Factors that impact producing beef carcasses with optimum traits are numerous but start with genetic selection. It is well established that some breeds have a greater genetic potential for high levels of marbling and related higher USDA Quality Grades, while other breeds are heavier muscled and tend to have less trimmable fat. In general, breeds of British origin, which include Angus, Hereford and others, have better quality grades, while breeds of continental origin, including Simmen tal, Charolais and others, have more desirable yield grades. Brahman-type

stops growing earlier in life than “late” maturing cattle. When the skeleton and muscle stop or slow, fat is more quickly added to the carcass, both subcutaneous or trimmable fat and marbling. Early maturing cattle almost always have lower (smaller) frame scores. It is one of the basic truths about genetics that there is more variation within breeds than between breeds, meaning that when selecting genet ics, producers can’t just decide to add a different breed to change genetic composition, but must select cattle within the breed that possess the traits they are trying to obtain. Further complicating decisions about genetic selection is that almost all traits are linked in various ways. For example, if selecting cattle for increased weaning weights, it is very easy to inadver tently select for larger frame sizes at the same time. If selection pressure is done for carcass traits, some other production traits such as reproduction may be affected. After genetics, the production practices that most affect carcass traits are time on feed and age of the animal at harvest. Obviously, for the vast majority of cattle, longer feed ing times on a high-concentrate or grain diet result in heavier carcasses with more fat, and typically higher marbling scores. Age at harvest is also important, as yearlings that have often been backgrounded or grown on pasture or forage will typically have heavier carcass weights, less trim mable fat and more marbling when compared to calves of similar genetics that entered the feedlot at weaning. Research conducted by North Dakota State University (NDSU) at the Dickinson Research Extension Center investigated the role of frame size and production practices on carcass traits. The cattle used were either

Table 1 Frame Score

Medium Large Medium Small Small

Final Weight, pounds

1,749

1,669

1,305

Hot Carcass Weight, pounds 1,050

999

782

Dressing Percentage

60

60

60

Marbling Score

479 (Low Choice)

526 (Average Choice)

547(Average Choice)

12th Rib Fat Depth, inches

0.37

0.41

0.39

Ribeye Area, sq. inches

15.72

14.37

13.35

USDA Yield Grade

2.77

3.00

2.55

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