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2010 State Fair of Virginia Lamb Carcass Evaluation Summary

Authors as Published

Dr. Scott P. Greiner, Extension Animal Scientist, VA Tech

Since 1999, more than 2100 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 lambs 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 LMA 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 loin muscle 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 in early October (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 CategoryDescriptionCarcass and ADG Parameters
GoldLambs with both outstanding carcass merit and growth> 50.0 %BCTRC & > 0.45 ADG
PurpleLambs with superior carcass merit and desirable growth> 50.0 %BCTRC with ADG < Gold standard or 49.0-49.9% BCTRC with > 0.41 ADG
BlueLambs with desirable carcass meritCarcasses not meeting Gold or Purple criteria with > 47.5 %BCTRC
RedLambs meeting carcass standards but have less desirable combination of leanness and LMAAll carcasses with %BCTRC < 47.5
PinkLambs which are over-finished or under-finished, and/or have small LMA relative to their weightCarcasses failing to meet one or more of the standards listed above

The following table summarizes the carcass information since beginning the program. Over the last 12 years, live weights and carcass weights of lambs have gotten heavier. Associated with this weight increase has been a corresponding increase in ADG, loin muscle area, and fatness. While a portion of the increase in LMA 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 LMA standard for their carcass weight compared to the first few years of the contest.

The last two years (2009 and 2010), lambs have gotten heavier and fatter. Compared to the five-year average, in both 2009 and 2010 there were more lambs which were overfed as indicated by the increased percentage of Yield Grade 4 lambs as well as more lambs failing to meet the minimum LMA standard. Both years had more very heavy carcasses (85 pounds and greater) as well. As a result of these factors, less lambs qualified for the Gold, Purple and Blue premium categories.

Rights


Virginia Cooperative Extension materials are available for public use, re-print, or citation without further permission, provided the use includes credit to the author and to Virginia Cooperative Extension, Virginia Tech, and Virginia State University.

Publisher

Issued in furtherance of Cooperative Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department of Agriculture cooperating. Alan L. Grant, Dean, College of Agriculture and Life Sciences; Edwin J. Jones, Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg; Jewel E. Hairston, Administrator, 1890 Extension Program, Virginia State, Petersburg.

Date

November 1, 2010


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