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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.) x 100 = 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 2
USDA 3 – Industry average
USDA 4
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:

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

1. 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.

Adjust the preliminary yield grade by 0.3 for every square inch 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 then the adjustment is added. PYG Adj. = (Required REA - Actual REA) x 0.3

1. 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

Example

Fat Thickness = .2 in.
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

Answer

Preliminary Yield Grade = 2.5
Adjustment for REA = -.7
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 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. 

• Classification
• Young Cattle
• 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.

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

• Prime
• Choice
• Select
• Standard

Beef Practice