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2008 State Fair of Virginia Lamb Carcass Evaluation Summary
Livestock Update, November 2008
Scott P. Greiner, Ph.D., Extension Animal Scientist, VA Tech
Over the past ten years, more than 1885 lambs have been evaluated through the Lamb Carcass Contest held in conjunction with the youth market lamb show at the State Fair of Virginia. The program serves as an educational tool for exhibitors and breeders regarding factors that influence the production of lean lamb that fits industry and consumer targets.
Five premium categories (Gold, Purple, Blue, Red, and Pink) have been established to rank lambs based on their combination of carcass merit and growth performance. The following standards were utilized, with carcasses failing to meet one or more of these qualifications placed in the Pink group:
Minimum fat thickness of 0.10 in.
Maximum fat thickness of 0.35 in. (maximum Yield Grade of 3.9)
Minimum REA for carcass weight using formula: 1.4 + (0.02 x HCW)
Minimum Quality Grade of Choice-
Minimum carcass weight of 45.0 pounds
Carcasses meeting all of the above standards were ranked using carcass merit (determined by percentage boneless, closely trimmed retail cuts- %BCTRC) and live average daily gain (ADG). The formula to estimate %BCTRC utilizes carcass weight, fat thickness, body wall thickness, and ribeye area and represents the predicted proportion of the carcass that is saleable retail product. Average daily gain is calculated for each lamb from the time of nomination in late June to the State Fair (approximately 100 days). The average ADG of all lambs exhibited in the live show serves as the benchmark ADG value within year. Carcass premium categories were established as follows:
Premium Category |
Carcass and ADG Parameters |
Gold |
> 50.0 %BCTRC & > 0.45 ADG |
Purple |
> 50.0 %BCTRC & ADG < 0.45 |
Blue |
> 49.0 %BCTRC & ADG < average |
Red |
> 47.5 %BCTRC & ADG < average |
Pink |
Carcasses failing to meet one or more of the standards |
The following table summarizes the carcass information from the State Fair during the ten years the program has been conducted. Live and carcass weights of lambs over the past five years (2004-2008) are heavier compared to lambs exhibited in 2003 and prior. Associated with this weight increase has been a corresponding increase in ribeye area. While a portion of the increase in REA is directly related to weight, the lambs have also improved in overall muscling, as indicated by a higher percentage of the lambs meeting the minimum REA standard for their carcass weight. Despite the increases in weight over time, fat thickness and overall cutability (%BCTRC) have remained relatively constant. A very high percentage of the carcasses are yield grade 1 and 2, and the low percentage of undesirable yield grade 4 carcasses is much more favorable than industry average.
The increasing percentage of carcasses in the Gold, Purple, and Blue premium categories would suggest that exhibitors are more effectively selecting, feeding, and managing their lambs to reach a desirable target endpoint. This is confirmed by the general trend for a lower percentage of Pink premium category lambs (lambs disqualified for not meeting minimum carcass specifications).
STATE FAIR OF VIRGINIA LAMB CARCASS CONTEST SUMMARY 1999-2008
