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Carcass Grading points?

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BuckJones

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It's been a while since I have seen any carcass grading results...I think since my last steer in '07. But if I remember correctly, each of the carcass merrits is awarded points. I've tried to find these pointing systems, but no such luck. They aren't a figment of my imagination are they?
I remember my last one was 8 mm fat cover, and got 10 points. Year before that, it was I think 9, with also 10 points. I'll have to dig around for the papers.
I'm wondering because there is a difference in interpretation in the results of the clubs gradings. We only had one steer grade prime...but he only had 4 mm of fat cover...so the newer folks thought that that was the ideal ammount of fat and anything over is too fat. The carcass gradings used to come with points, and I noticed that steers with 8 and 9 mm get 10...while higher or lower ammounts get lesser points...but website says anything over 2mm is acceptable.
 
In Canada Prime refers to a marbling level that is equivalent to USDA prime. This is the fat interspersed through the meat. AAA is one step below and is roughly USDA choice. AA is below that and A is the least.
In Canada a carcass has to have at least 2mm of backfat (gradefat) in order to qualify as an A grade carcass. This is because the fat is required in order to control the chilling speed of the carcass in the cooler. If an animal has less than that, it is downgraded to a B1 grade and suffers a severe discount (programs like Laura's Lean want B1). As you add backfat the yield of the carcass goes down rapidly. In order to qualify as a Y1 the carcass must yield> 58%, Y2 54-58% and Y3 is < 54%.
There is nothing wrong with 7mm of backfat (roughly 1/2 inch), but the carcass will likely yield slightly less than the same weight carcass with only 4mm of fat. Most feeders are working towards this 1/2 inch mark before they ship cattle as they are trying to hit the mainstream marketplace that rewards AAA and steeply discounts A cattle. They use the backfat as an estimate of fat deposition which should roughly mean adequate marbling levels.
 
They changed the grid so that a AAA Y3 is no longer a premium-I'll have to dig out my last kill sheet to see what are all at even money.
 
Hmm. Had a look at the yield page on that website, Dylan. Looking at their equation:
Lean % = 63.65 + 1.05 (muscle score) - 0.76 (grade fat)

How do they come up with Muscle score and grade fat? Their ruler is helpless to someone who has no clue how to interpret it. :p

Our angus and other X calves typically grade well. But i'm mainly wondering about this because our Limos usually yield >60% with backfat of usually 8-10 mm, but no marbling. I'm thinking this is just because of the breed trait to be lean?
 
the muscle score is a subjective assessment of the muscle over the rump. That is what they use at line speeds. If they are calculating yields (such as in research cattle) they use the equation
LY = 57.96-(.027xCWT)+(.202xREA)-(.703xBF)
CWT is carcass wt in kg, REA is rib-eye in sq cm and BF is average back fat (average of 3 measurements of fat around the eye)
The muscle score is largely to keep flat muscled dairy beef out of the mainstream production line.
Grade fat is taken by hooking the ruler over the fat in the fourth quadrant of the rib-eye. (Grade fat is one of the three measures used to calculate average fat).
 

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