© American Meat Science Association. www.meatandmusclebiology.com This is an open access article distributed under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Meat and Muscle Biology™ Characterizing Ham and Loin Quality as Hot Carcass Weight Increases to an Average of 119 Kilograms 1,2,3 Hannah E. Price 4 , Annie B. Lerner 5 , Emily A. Rice 5 , Jessica E. Lowell 4 , Bailey N. Harsh 4 , Kayla E. Barkley 4 , Lauren T. Honegger 4 , Elaine Richardson 4 , Jason C. Woodworth 5 , Mike D. Tokach 5 , Steve S. Dritz 6 , Robert D. Goodband 5 , Joel M. DeRouchey 5 , Travis G. O’Quinn 5 , Matt W. Allerson 7 , Brandon Fields 8 , David A. King 9 , Tommy L. Wheeler 9 , Steven D. Shackelford 9 , Anna C. Dilger 4 , and Dustin D. Boler 4 * 4 Department of Animal Sciences, University of Illinois, Urbana-Champaign, IL 61801, USA 5 Department of Animal Sciences and Industry, Kansas State University, Manhattan, KS 66506, USA 6 Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA 7 Holden Farms, Inc., Northfeld, MN 55057, USA 8 Pig Improvement Company, Hendersonville, TN 37075, USA 9 USDA, ARS, U.S. Meat Animal Research Center, Clay Center, NE 68933, USA *Corresponding author. E-mail address: dboler2@illinois.edu (D.D. Boler) Abstract: The objective was to characterize ham and loin quality of carcasses ranging from 78 to 145 kg (average ~119 kg). Hot carcass weight (HCW), back fat depth, and loin depth was measured on 666 carcasses. Loin pH, instrumental and visual color and iodine value of clear plate fat (all 3 layers) was measured on approximately 90% of the population. Quality mea- surements of the ham, 14 d aged loin and chop, and loin chop shear force (SSF) were evaluated on approximately 30% of the population. Myosin heavy chain fber type determination was completed on 49 carcasses. Slopes of regression lines and coef- fcients of determination between HCW and quality traits were calculated using the REG procedure in SAS and considered signifcantly diferent from 0 at P ≤ 0.05. As HCW increased, loin depth (b 1 = 0.2496, P < 0.0001), back fat depth (b 1 = 0.1374, P < 0.0001), loin weight (b 1 = 0.0345, P < 0.0001), and ham weight (b 1 = 0.1044, P < 0.0001) increased. Estimated lean (b 1 = –0.0751, P < 0.0001) and iodine value (b 1 = –0.0922, P < 0.0001) decreased as HCW increased, where HCW accounted for 24% (R 2 = 0.24) of the variation in estimated lean and 7% (R 2 = 0.07) of the variation in iodine value. However, HCW did not explain variation in ham quality traits (P > 0.15) and did not explain more than 1% (R 2 ≤ 0.01) of the variation in 1 d loin color or pH. Loins from heavier carcasses were more tender (decreased SSF; b 1 = –0.0674, P < 0.0001), although HCW only explained 9% of the variation in SSF. Hot carcass weight did not alter (P > 0.22) muscle fber type percentage or area. These results suggest that increasing HCW to an average of 119 kg did not compromise pork quality. Introduction Between 1995 and 2018, average hot carcass weight of U.S. pork carcasses increased from 82 to 96 kg (USDA ERS, 2018), which is an increase of approximately 17%. If current rates of carcass weight increases persist over time, the average pork carcass weight in the United States will be 105 kg by the year 2030 and over 118 kg by 2050. Although this represents an increase in throughput efciency due Keywords: color, heavy pigs, hot carcass weight, pork quality, tenderness Meat and Muscle Biology 3(1):330–343 (2019) doi:10.22175/mmb2019.06.0019 Submitted 14 June 2019 Accepted 23 July 2019 1 Funding was partially provided by The National Pork Board. 2 Mention of trade names, proprietary products, or speci- fed equipment does not constitute a guarantee or warranty by the USDA and does not imply approval to the exclusion of other products that may be suitable. 3 The USDA is an equal opportunity provider and employer. Published September 5, 2019