- Yield Grade = 2.5 + (2.5 × BF) + (0.2 × % KPH) + (0.0038 × HCW) - (0.32 × REA)
Calculate the values within the parenthesis first and then add or subtract as necessary.
If you do not have a calculator on hand, YGs can be calculated using a series of adjustments based on BF, REA, KPH and HCW.
STEP 1
Backfat is converted into a preliminary YG (PYG) value. Preliminary YG measurements start at 2.0, and 0.25 is added to the PYG measurement for every 0.1 inches of backfat (Table 1).
Table 1
| Backfat (inches) | PYG |
|---|
| 0 | 2.0 |
| .2 | 2.5 |
| .4 | 3.0 |
| .6 | 3.5 |
| .8 | 4.0 |
| 1.0 | 4.5 |
| 1.2 | 5.0 |
| 1.4 | 5.5 |
STEP 2
Determine the required REA based on HCW. A 600-pound HCW requires a 11.0 in.2 REA. For every 25 pound increase in HCW, the required ribeye area increases by 0.3 in.2. For each 1 in.2 more than the required REA, subtract 0.3 from the PYG. For every 1 in.2 less than the required REA, add 0.3 to the PYG. Below are two tables to help determine required REAs.
Table 2.1
| HCW (lbs.) | Required REA (in.2) |
|---|
| 600 | 11.0 |
| 650 | 11.6 |
| 700 | 12.2 |
| 750 | 12.8 |
| 800 | 13.4 |
| 850 | 14.0 |
| 900 | 14.6 |
| 950 | 15.2 |
| 1000 | 15.8 |
Table 2.2
| HCW (lbs.) | Required REA (in.2) |
|---|
| 600-608 | 11.0 |
| 609-616 | 11.1 |
| 617-224 | 11.2 |
| 225-633 | 11.3 |
STEP 3
Adjust for % KPH. KPH measurements start at 3.5%, and for every 0.5% above 3.5%, add 0.1, and for every 0.5% below 3.5%, subtract 0.1 (Table 3).
Table 3
| KPH (%) | Adjustment |
|---|
| 4.5 | +0.2 |
| 4.0 | +0.1 |
| 3.5 | 0 |
| 3.0 | -0.1 |
| 2.5 | -0.2 |
| 2.0 | -0.3 |
| 1.5 | -0.4 |
| 1.0 | -0.5 |
Final YG values for industry purposes are always rounded down, so a calculated YG of 3.9 is still a YG 3 carcass.
Below is an example of how to calculate a YG using this method.
Example
Carcass Characteristics:
Backfat = 0.4 inches, HCW = 700 lbs., Actual REA = 14.0 in.2, KPH = 2%
- PYG = 3.0
- Required REA = 12.2
- Ribeye adjustment = 12.2 - 14.0 = -1.8 × 0.3 = -0.54
- KPH adjustment = -0.3
- YG = 3.0 - 0.54 - 0.3 = 2.16 = YG 2
Source : sdstate.edu