Harvest season, carcass weight, and fat measurements effects on lamb carcass characteristics and economic comparison of moderate and heavy weight lamb carcasses in the Western lamb processing industry

Authors: WHALEY, JAELYN - University Of Wyoming; MEANS, WARRIE - University Of Wyoming; RITTEN, JOHN - University Of Wyoming; Murphy, Thomas - Tom; GIFFORD, CODY - University Of Wyoming; CUNNINGHAM-HOLLINGER, HANNAH - University Of Wyoming; WOODRUFF, KELLY - University Of Wyoming; MCKIBBEN, HEATHER - University Of Wyoming; PAGE, CHAD - University Of Wyoming; STEWART, WHIT - University Of Wyoming

Submitted to: Journal of Animal Science
Publication Type: Proceedings
Publication Acceptance Date: 5/19/2020
Publication Date: 11/30/2020
Citation: Whaley, J., Means, W., Ritten, J., Murphy, T., Gifford, C., Cunningham, H., Woodruff, K., McKibben, H., Page, C.M., Stewart, W.C. 2020. Harvest season, carcass weight, and fat measurements effects on lamb carcass characteristics and economic comparison of moderate and heavy weight lamb carcasses in the Western lamb processing industry [abstract]. Journal of Animal Science. 98(4):190-191. https://doi.org/10.1093/jas/skaa278.351.
DOI: https://doi.org/10.1093/jas/skaa278.351

Interpretive Summary: Lamb harvest in the intermountain west region was surveyed from May 2018 through May 2019, and a total of 9,532 lamb carcasses were evaluated. Using digital images, hot carcass weight, 12th rib fat thickness, ribeye area, body-wall thickness, and USDA yield grade were captured. Additional variables included calculated yield grade and percent boneless closely trimmed retail cuts. Costs and returns were collected from both public and private sources to estimate packer profitability between varying carcass sizes using Monte Carlo simulation. Average hot carcass weight from sampled lambs indicated most exceeded the upper threshold of U.S. packer preferences (65 to 85 lb). According to USDA, ideal 12th rib fat thickness is 0.25 inches, and 66% of lamb carcasses in the present survey exceeded that level. Based on current costs and a marketing system without premium or discounts for the carcass weights used in this analysis, increased profitability of processing a 100 lb carcass compared to 70 lb was $0.17 ± $14.59. Quantitative, economic comparison shows that additional yield offsets additional costs of heavy carcasses.

Technical Abstract: Carcass characteristics and economic impact estimates of over-finished lambs on the processing sector were evaluated in two commercial Intermountain West abattoirs. Lamb carcasses were surveyed throughout the year using digital images and imaging software (n = 9,532). Estimations of abattoir costs and returns included loading labor, downtime cost, price of fat, live and carcass trucking costs from the two largest lamb processers in the Intermountain West. Profitability comparisons were made using Monte Carlo simulation models replicating live and carcass prices for distributions based on historical pricing data to assess overall profitability of a carcass in an ideal weight range (29.5 - 39.0 kg) and a carcass that exceeds ideal weight (>39.0 kg). Overall means show that the average lamb carcass exceeded packer preferred hot carcass weight (40.76 ± 9.29 kg) and industry acceptable 12th rib fat thickness (8.17 ± 3.79 mm). There were seasonal differences in hot carcass weight and fat measurements with carcasses being lighter weight (P = 0.05) and trimmer (P = 0.05) in the summer months. Monte Carlo simulation found that the additional yield from heavier carcasses offset costs of harvesting them. However, factors such as machine wear and increased labor turnover rates should be considered, although difficult to quantify. Collectively, the current study shows that U.S. lamb carcasses are too heavy and excessively fat but have minor effect on processor profitability.