Economically important traits for beef cattle evaluation that will be discussed are: 1) live weight; 2) dressing percent; 3) muscling; 4) fat thickness; 5) yield grade; and 6) quality grade.

Live Weight – Beef Cattle have a wider range of market weights than other species due to differences in type and maturity.
                Normal Range:  950-1500 lb.
                Average:   1150 lb.

Dressing percent – Dressing percent is important because it reflects the amount of carcass in relation to the animal’s live weight. Dressing percent is calculated by using the following formula:
                                            Hot Carcass Wt. x 100 = Dressing %
                                            Live Animal Wt.
Dressing percent is affected by the fill, finish, muscling, sex, type, and if the animal is pregnant or not.
                Normal Range:  55-67% for steers and heifers
                Average:   62% for Choice steers and heifers

Muscling – Muscling can be estimated visually by a number of traits. A good indication of total carcass muscle is the ribeye. Generally, an average beef steer has approximately 1.1 sq. in. of ribeye area per 100 lb. live weight. For example – a 1,000 lb. steer should have an 11.0 sq. in. ribeye.
                Normal Range: 10 – 18.0 in²
                Average:   12.6 in² for a 1150 lb. steer; 11.6 in² for a 1150 lb. heifer

Fat Thickness – The primary estimate of fatness is fat thickness at the 12^th rib. It is used to assess total fat on the carcass.
                Normal Range:  .15 - .8 in.
                Average:   .5 in.

Yield Grade – Yield Grade is an estimate of percent retail yield of the four primal cuts of beef (chuck, rib, loin, and round) and is also known as cutability. Yield Grade identifies the difference in the yield of lean red meat to waste fat. (Figure 14)
                USDA 1 – Most desirable, trim
                USDA 2
                USDA 3 – Industry average
                USDA 4
                USDA 5 – Least desirable, excessively fat
Yield grade is based on the four following traits:
                1) hot carcass weight
                2) fat thickness at the 12^th rib
                3) percent of kidney, heart, pelvic fat
                4) ribeye area

The following is a three-step method for calculating yield grade:

1) A preliminary yield grade is first determined solely on 12^th rib fat thickness. PYG = 2.0 + (2.5 x fat thickness)

2) Adjust the preliminary yield grade using the estimates of ribeye area and carcass weight. Carcass weight of the animal can be calculated by estimating the animal’s dressing percent and multiplying it by the live weight of the animal.

Adjust the preliminary yield grade by 0.3 for every 1.0 sq. in. change in ribeye from the size given for a particular carcass weight. If you estimate an animal to be above average in muscling, the adjustment is subtracted from preliminary yield grade; if below average in  muscling, then the adjustment is added.
                    PYG Adj. = (Required REA – Actual REA) x 0.3

3) Estimation of percent kidney, pelvic and heart fat (KPH%) in live steers is extremely difficult to asses with consistent success. The average KPH% for an average steer is 2.5%. Thus, the adjustment for every 1.0% change above or below 3.5% is .2 of a yield grade. If internal fat is above 3.5%, the adjustment factor is added; if below, the adjustment factor is subtracted.
                    PYG Adj. = (Actual KPH – 3.5) x .02

        Example:
                Fat Thickness = 0.2 in.                     Preliminary Yield Grade =   2.5
                Ribeye Area = 14.5 sq. in                Adjustment for REA =         -.7
                (Live wt. = 1,130 lb., dressing
                percent is estimated at 62%,
                thus carcass wt. = 700 lb.)
                Percent Internal Fat = 2.5%            Adjustment Factor =            -.2
                                                                                  Final Yield Grade = 1.6

Quality Grade – Quality is important in meat products to insure customer satisfaction. Quality can be identified as those factors that affect the palatability of tastefulness, flavor and juiciness of the meat. Quality grading of beef carcasses is determined by two subjectively scored factors in all cases where color, texture, and firmness of lean are normal. (Figure 15)

Maturity – is the physiological age of the carcass. Maturity is important since the tenderness of lean muscle decreases as the animal advances in age. It is measured by the degree of ossification of the vertebrae.

Marbling – The amount of fat within the muscle is known as marbling or intramuscular fat. The marbling is scored in the ribeye muscle at the 12^th rib. There are nine degrees of marbling and they are listed from the least amount to the highest. (Click on marbling score for example)
            1. Practically Devoid                     6. Moderate
            2. Traces                                          7. Slightly Abundant
            3. Slight                                            8. Moderately Abundant
            4. Small                                             9. Abundant
            5. Modest

Maturity and marbling are evaluated and combined to determine the final quality grade. These eight quality grades of beef are shown below.

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