The Agricultural Marketing Act of 1946 originally mandated the standards for feeder-calf grades. Changes were made to the grading standards for live feeder cattle in October 2000. They offer a valuable tool for marketing of cattle and calves and certify the grades used to make contracts for cattle on the futures market.

The grade of feeder cattle is determined by evaluating three general value-determining characteristics: frame size, thickness and thriftiness.

• Frame size is a skeletal measurement that considers height and body length in relation to age.

• Thickness refers to the development of the animal's muscling in relation to its skeletal size.

• Thriftiness is an appraisal of the apparent health of the animal and its ability to grow and fatten normally.

Frame-size standards for thrifty feeder cattle are assigned one of three marks, L (large frame), M (medium frame) and S (small frame). Large-frame steers and heifers are expected to reach a U.S. Choice carcass grade at Yield Grade 3 (about 0.5 in. of fat at the 12th rib) at a weight heavier than 1,250 lbs.

The thickness (muscling) grades range from Number 1-4. “Inferior” cattle are unthrifty and are not expected to perform normally in their present state and include those that are “double muscled.” Inferior cattle can have any combination of thickness and frame size.

Therefore, where we've had only four grades or so to concern ourselves with in the past, we now have 13. They are L1, L2, L3, L4, M1, M2, M3, M4, S1, S2, S3, S4 and Inferior. This will give potential buyers an even clearer picture of the calves offered for sale.

Producers and buyers alike will benefit as the entire beef industry looks to improve the quality and consistency of the product that eventually finds its way to the dinner table.

A classic Colorado study (Table 1) compared performance of steers of each of the USDA Feeder Grade frame sizes. Small-, medium- and large-frame steers were fed a finishing ration for 135 days.

It is important to note that while large-frame steers had more rapid gains than small-frame steers, the small-frame steers were the most efficient. Although it may seem odd that faster-gaining cattle could be less efficient, two facts must be considered.

• First, large cattle require more feed for maintenance and thus must gain faster to maintain equal feed efficiency.

• Second, the final backfat thicknesses for all three frame sizes in the Colorado trial were similar, indicating all the cattle were slaughtered at about the same physiological maturity and carcass composition. Quality grade also decreased as frame size increased.

Frame score is considered to be moderately to highly heritable. As such, selection can significantly change frame scores, primarily achieved through sire selection. With a heritability estimate of 0.40, about 40% of a bull's difference in frame score from herd average will appear in the progeny.

Frame-score measurements are descriptive of animal type and growth patterns in beef cattle. They are useful in evaluating animal nutritional requirements and characterizing target market weights, and aid in selection decisions. A certain amount of sorting may be required for each group to attain their optimum carcass weight and not be overfed or underfed.

Table 1. Feedlot performance of small, medium and large frame steers

Frame score Small Medium Large
Initial weight (lb.) 651 770 880
Final weight (lb.) 1,016 1,186 1,313
Daily gain (lb./day) 2.7 3.1 3.2
Feed intake (lb.) 19.1 22.3 24.1
Feed-to-gain 7.0 7.2 7.4
Carcass weight (lb.) 621 739 817
Fat thickness (in.) 0.5 0.5 0.5
Ribeye area (in.2) 11.9 12.8 13.9
Yield Grade 2.8 3.0 2.9
Quality Grade* 6.1 5.8 5.6
*5 = USDA low Choice, 6 = USDA average Choice

Source: Colorado State University