Economically important traits for beef cattle evaluation discussed below are live weight, dressing percent, muscling, fat thickness, yield grade and quality grade.
Live Weight — Beef cattle have a wider range of market weights compared to other species due to differences in type and maturity. The normal range is 950-1500 pounds with an average weight of 1150 pounds.
Dressing Percent — 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./Live Animal Wt.)X100=Dressing percent
Dressing percent is affected by the fill, finish, muscling, sex, type and if the animal is pregnant or not. The normal range for steers and heifers is 55-67 percent with an average of 62.
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 square inches of ribeye area per 100 pounds live weigh. For example, a 1000 lb. steer should have an 11 sq. inch ribeye. The normal range is 10-18 sq. inches with an average of 12.6 for a 1150 lb steer and 11.6 for a 1150 lb. heifer.
Fat Thickness — The primary estimate of fatness is fat thickness at the 12th rib. It is used to assess total fat on the carcass. The normal range is .15-.8 inches with an average of .5 in.
Yield Grade — Yield grade is an estimate of the percent retail yield of the four primal cuts of beef (chuck, rib, loin and round). It is also known as cutability.
Yield grade identifies the difference in the yield of lean red meat to waste fat based on the following scale:
USDA 1 – Most desirable, trim
USDA 3 – Industry average
USDA 5 – Least desirable, excessively fat
Yield grade is based on the four traits: hot carcass weight, fat thickness at the 12th rib, percent of kidney, heart and pelvic fat, and ribeye area. The following is a three-step method for calculating yield grade:
- A preliminary yield grade (PYG) is first determined solely on the 12th rib fat thickness. PYG=2.0+(2.5 X fat thickness)
|Thickness of Fat Over Ribeye, in.
||Preliminary Yield Grade
- Adjust the preliminary yield grade using the estimate of ribeye area and carcass weigh. 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.
|Carcass Weight (lb.)
||Required Ribeye Area
- Estimation of percent kidney, pelvic and heart fat (KPH%) in live steers is extremely difficult to assess with consistent success. The average KPH% for a steer is 2.5 percent. Thus, the adjustment for every 1 percent change above or below 3.5 percent is .2 of a yield grade. If internal fat is above 3.5 percent, the adjustment factor is added; if below, the adjustment factor is subtracted. PYG Adj.=(Actual KPH–3.5) x .2
Ribeye Area=14.5 sq. in.
Live Weight=1130 lb., dressing percent is estimated at 62%
Carcass Weight=700 lb.
Percent Internal Fat=2.5 percent
Preliminary Yield Grade=2.5
Adjustment for REA=-.7
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 on beef carcasses is determined by two subjectively scored factors in all cases where color, texture, and firmness of lean are normal.
Maturity — 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.
|Approximate Age (months)
|| Mature Cattle
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 12th rib. There are nine degrees of marbling and they are listed from the least amount to the highest.
- Practically Devoid
- Slightly Abundant
- Moderately Abundant
Maturity and marbling are evaluated and combined to determine the final quality grade. These eight quality grades of beef are shown below