Skip to main content
ARS Home » Research » Publications at this Location » Publication #333064
Title: Comparison of ultrasound and actual beef carcass measurements as influenced by stockering performance and finishing system

Author
item Neel, James
item SWECKER JR., WILLIAM - Virginia Polytechnic Institution & State University
item BROWN, MICHAEL - Retired ARS Employee

Submitted to: Journal of Animal Science and Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/15/2019
Publication Date: 4/19/2019
Citation: Neel, J.P., Swecker Jr., W.S., Brown, M.A. 2019. Comparison of ultrasound and actual beef carcass measurements as influenced by stockering performance and finishing system. Journal of Animal Science and Research. 3(2). https://doi.org/10.16966/2576-6457.128.
DOI: https://doi.org/10.16966/2576-6457.128

Interpretive Summary: Angus-crossbred steers (n = 216) were used in a three-year study to assess the effects of winter stocker growth rate and finishing system on beef carcass parameters as measured by ultrasound, a USDA grader at a commercial slaughter facility, and laboratory analysis. During winter months (December to April) steers were randomly allotted to one three stocker growth rates: 1) Low, 2) medium, or 3) high. Upon completion of the winter phase, steers were randomly allotted within each stocker treatment to either a corn silage-concentrate or pasture finishing system. All steers, regardless of finishing treatment, were finished to an equal-time endpoint to eliminate confounding of treatments with animal age or seasonal factors. Upon completion of the finishing period, live animals were ultrasounded to obtain estimates of loin muscle intramuscular fat percent, ribeye area, rib fat, and rump fat. Animals were then harvested and carcass data collected. Our results clearly demonstrate that ultrasound measurement was unable to identify changes in loin muscle intramuscular deposition due to stockering plane of nutrition, whereas laboratory analysis and the USDA grader could identify changes in loin muscle intramuscular deposition due to stockering plane of nutrition. The implications to this observation include that, when relying on ultrasound for intramuscular fat estimation: 1) unreliable breakevens could result if cattle are fed to a specific USDA quality grade endpoint; 2) under-estimation of marbling capability for individual animals may occur within contemporary groups when animals originate from different sources/backgrounds; 3) unreliable research conclusions may occur when utilizing ultrasound intramuscular measurements.

Technical Abstract: Angus-crossbred steers (n = 216) were used in a three-year study to assess the effects of winter stocker growth rate and finishing system on beef carcass parameters as measured by ultrasound, a USDA grader at a commercial slaughter facility, and laboratory analysis. During winter months (December to April) steers were randomly allotted to one three stocker growth rates: low (0.23 kg d-1; LOW), medium (0.45 kg d-1; MED), or high (0.68 kg d-1; HIGH). Upon completion of the winter phase, steers were randomly allotted within each stocker treatment to either a corn silage-concentrate (CONC) or pasture (PAST) finishing system. All steers, regardless of finishing treatment, were finished to an equal-time endpoint to eliminate confounding of treatments with animal age or seasonal factors. Upon completion of the finishing period, live animals were ultrasounded to obtain estimates of loin muscle intramuscular fat percent (US-IMF), ribeye area (US-REA), rib fat (US-RF), and rump fat (US-RP). Animals were then harvested in two groups (one half of pasture and one half of feedlot cattle each time) and carcass data collected. Data were analyzed utilizing mixed models procedures including fixed effects of year, stockering treatment, finishing treatment, harvest date, estimate type (carcass vs. ultrasound), and their interactions and random effects of rep nested in year and finishing treatment, rep nested in year, stockering treatment, and finishing treatment, rep x harvest date nested in year, stockering treatment, and finishing treatment, and a random residual effect. Covariance analyses were performed to determine the predictability of on-floor USDA grader measurements and chemical analytical results from ultrasound estimates. Ultrasound-IMF measurement detected a finishing system effect (P<0.0001) but no evident impact of stocker system. Laboratory determined IMF (actual-IMF) resulted in detection of both a stocker treatment and finishing system effect (P<.05). Ultrasound overestimated IMF content (P<0.05) for all treatment subgroups except within HIGH-CONC, where both measurement types were in agreement. When actual-IMF and US-IMF were each converted to a USDA quality grade (QG) equivalent, and compared with the USDA grader QG (grader-QG), US-QG and grader-QG overestimated (P<0.05) actual IMF-QG for all treatment subgroups except HIGH-CONC., where US- and actual-QG were in agreement. Grader-QG and actual IMF-QG detected both stockering and finishing treatment effects, while US-QG did not. Our results clearly demonstrate that US-IMF measurement was unable to identify changes in loin muscle IMF deposition due to stockering plane of nutrition, whereas laboratory analysis and the USDA grader could identify changes in loin muscle IMF deposition due to stockering plane of nutrition.