WHE: Grading Grids
   
Grids & Grading

Overview - Hog Carcass Grading Grid

The Grading Grid brings together two pork value factors, dressed Carcass Weight and Estimated Percent Lean Yield, into the form of a grading grid. The highest grade indexes within the grid have been established where the plant feels there is best carcass value and pig meat yield. The intersection of the dressed carcass weight and the calculated "Estimated Percent Lean Yield" within the grid establishes the grade index for a pork carcass.

Example Grid

Yield
Class
Number
Estimated
Lean Yield
Percentage
0 -
67.9
kg
68 -
72.9
kg
73 -
77.9
kg
78 -
82.9
kg
83 -
87.9
kg
88 -
92.9
kg
93 -
97.9
kg
98 -
102.9
kg
103 -
107.9
kg
108 -
111.9
kg
112 -
116.9
kg
117 -
999
kg
164.3 - 10010105075959510010010010010050
263 - 64.29101050759510310910910710510050
361.8 - 62.99101050759510811311311110710050
460.7 - 61.79101050759511011611611310910050
559.6 - 60.69101050759511011611611310910050
658.6 - 59.5910105075951091141141111089550
757.7 - 58.5910105075951031091091071059050
856.9 - 57.6910105060859510410495908050
956.1 - 56.89101050607090959590807050
100 - 56.09101050606070707070606050

Calculating Estimated Percent Lean Yield

Yield (Estimated Percent Lean Yield) is governed by a mathematical formula that is based on extensive carcass cutouts. The equation has two variables, fat thickness and lean depth measured by the Destron Electronic Probe. Fat is the most influential factor of the two used to determine “Estimated Percent Lean Yield”. Fat measurements from the Destron probe accounts for over 90% of the variation in the lean yield percentage calculation while the lean measurement only provides a small modifying influence, in the formula. Generally, the lower the fat measurement the higher the “Estimated Lean Yield Percentage”.

The Electronic probe is inserted through the skin on the left side of the carcass at a point 7cm lateral to the center of the spine between the 3rd and 4th last ribs (Figure 11a & 11b). The probe must travel through the loin muscle of the carcass and emerge 2cm lateral to the junction of the ribs and the lateral spinal process (Figure 13). The probe has passed through the deepest part of the loin (Figure 12).

Image of Probe Insertion From Behind Grader
Figure 11a - Probe Insertion
Image of Probe Site Insertion From Behind Destron
Figure 11b - Probe Insertion
Image of Probed Cross Section
Figure 12 - Cross Section
Image of Probe Emerging Through Carcass
Figure 13 - Probe Emergence

During the grading process, all fat and lean measurements are registered and stored electronically into a computer data base as the probe is withdrawn from the carcass.

Summary

To achieve the highest grade index premium from a Grading Grid:

  • Target the preferred dressed carcass weight range.
  • Target the preferred estimated lean yield by controlling fat at the market weight.