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Fat score (FS) is used for live animal assessment of slaughter animals. In New South Wales, fat score has also been adapted to assess the nutritional status of adult sheep, particularly in relation to flock reproduction targets.
GR measurement site
Scores are based on the tissue thickness (both fat and lean tissue) at the GR site. The GR measurement site is 110mm from the carcase midline over the 12th rib. This site is used as a reference point because it is easy to measure on both the live animal (by manual palpation) and the hot carcase and provides a good indication of the overall fatness (and yield) of the whole carcase.
For MSA sheepmeat processing, the fat score is also determined on the depth of tissue at the GR site.
Fat scoring explained
The table describes the fat score, the coverage of tissue at the GR site and what you will feel over the long ribs during fat scoring. To achieve a reliable score, have the sheep or lamb standing in a race or on liveweight scales. The scorer must work fingers through the wool to skin level before feeling for fat cover over the rib bones.
Fat scoring guide:
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Fat Score |
1 |
2 |
3 |
4 |
5 |
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GR tissue
depth
in mm
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0 to 5 mm Not
eligible for MSA
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6 to 10 mm
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11 to 15 mm
|
16 to 20 mm
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20 mm and over |
|
Feel at the
12th long
rib |
Individual ribs felt
easily.Cannot feel
any tissue over
the ribs |
Individual ribs easily
felt but some
tissue
present |
Individual ribs can
still be felt. Can
feel more tissue
over the rib
|
Can only just feel
ribs.There is fluid
movement of
tissue |
Ribs cannot be felt.
Tissue movement
very fluid |
Locating the GR site on both the live animal and the carcase
On the slaughter floor, GR is usually measured with a ‘cut and measure’ knife or AUS-MEAT probe.
Recording the score
Randomly score 25-50 sheep from the middle of the mob. Record the fat score of each sheep with an X on the chart. The middle score of the distribution is close to the average. In this example with 25 sheep, the median value is 3.0 but by using the chart you can see the average is just less than 3.0.
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| 1.0 |
1.5 |
2.0 |
2.5 |
3.0 |
3.5 |
4.0 |
4.5 |
5.0 |
Download the Fat Score Recording Worksheet (52 KB)
Fat score and dressing percentage
Higher fat score animals have a higher dressing percentage, as shown below:
Dressing percentages related to fat score
| |
Lambs |
Sheep |
Fat score
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Unweaned
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Weaned
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Wethers
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Ewes |
| 1 |
43% |
41% |
39% |
38% |
| 2 |
45% |
43% |
41% |
40% |
| 3 |
47% |
45% |
43% |
42% |
| 4 |
49% |
47% |
45% |
44% |
| 5 |
51% |
49% |
47% |
46% |
Source: MLA Live Assessment Yard Book – Sheep and Lamb
Time off feed:
When sheep are held off feed prior to sale, add the following to the dressing percentage figures above:
| 0-3 hours |
0 |
| 4-5 hours |
+1% |
| 6-8 hours |
+2% |
| 9-12 hours |
+2-3% |
| 13-24 hours |
+3.5-4.5% |
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