PROCEEDINGS - American Society of Animal Science

Proceedings, Western Section, American Society of Animal Science
Vol. 60, 2009
RELATIONSHIPS OF EXIT VELOCITY AND AVERAGE CHUTE SCORE WITH CARCASS TRAITS IN
FEEDLOT STEERS
A.R. Pepper 1 , R.M. Enns 1 , R.L. Weaber 2 , H. Van Campen 3 , G.H. Loneragan 4 , J.L. Salak-Johnson 5 , C.C.L. Chase 6 ,
R.K. Peel 1 , J.J. Wagner 1 , D.H. Crews, Jr. 1 , and E.J. Pollak 7
1 Department of Animal Sciences, Colorado State University, Fort Collins; 2 Division of Animal Science, University of
Missouri, Columbia; 3 Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins;
4 Department of Agricultural Sciences, West Texas A&M University, Canyon; 5 Department of Animal Sciences, University of
Illinois, Urbana; 6 Department of Biology and Microbiology, South Dakota State University, Brookings; 7 Department of
Animal Sciences, Cornell University, Ithaca
ABSRACT: The objective of this study was to estimate
relationships between temperament, as measured by exit
velocity and chute score, and carcass trait performance.
Crossbred steers (n=1,551) from three operational units of a
single ranch were transported approximately 8 hours from
western Nebraska to a commercial feedlot in southeast
Colorado over three days. Steers were housed overnight in
receiving pens before being processed and allocated to their
final pens (n=6) for the feeding period. Exit velocity and
chute score were measured at receiving (EV; m/s, CS) and
approximately 75 d later at re-implant (EV_RI; m/s,
CS_RI). Animals were harvested and carcass data collected
after 225 d on feed. Analyses were conducted using a
mixed effects model via the MIXED procedure of SAS.
Analyses evaluated the associations of EV, EV_RI, CS, and
CS_RI independently on hot carcass weight (HCW), fat
thickness (FAT), ribeye area (REA), kidney, pelvic and
heart fat (KPH), marbling score (MS), and USDA yield
grade (YG). All models included the fixed effect of ranchpen
class, and a random animal effect. An increase of 1m/s
in EV was associated with a 2.69 kg decrease (P < 0.05) in
HCW. An increase of 1 m/s in EV_RI revealed an
associated decrease in HCW of 2.29 kg (P < 0.01).
Similarly a one unit increase in CS was associated with a
decrease in marbling score (-4.3; P < 0.05), and a 0.03%
increase (P < 0.10) in KPH. All other regression estimates
were not significantly different than zero (P > 0.1). These
results suggest that cattle with more excitable temperaments
have lighter HCW, lower meat quality, and higher KPH
percentage.
Key Words: beef cattle, carcass traits, chute score, exit
velocity
Introduction
Temperament has been defined as an animal’s behavioral
response to handling (Nkrumah et al., 2007). Many
measures of temperament are very subjective and Burrow et
al. (1988) developed flight speed as an objective
measurement of temperament. Flight speed has been
defined as the time it takes for an animal to travel a
predetermined distance after exiting a confined area
(Burrow et al., 1988).
Docile animals are appreciated by producers in terms of
ease of handling; however this is not the only reason
selection may be practiced for more favorable
temperaments. Tulloh (1961) reported a favorable
relationship between live weight and docility in cattle.
Tulloh (1961) stated that selection based on live weight
would likely lead to an improvement in temperament.
Burrow (1997) stated that temperament is moderately
heritable, so selection for more docile animals should show
progress. Burrow and Dillon (1997) suggested that docile
animals grow faster in a feedlot than more excitable
animals because of increased feed intake, or because more
excitable animals might partition nutrients differently due
to avoidance behavior.
While research suggests that temperament measures are
heritable and related to growth measures, little information
exists relative to the relationship of temperament and
carcass performance; therefore, the objective of this study
was to determine the relationship between temperament, as
measured by exit velocity and chute score, and carcass trait
performance.
Materials and Methods
Crossbred steers (n=1,551), from three operational units
of a single Nebraska ranch were transported approximately
8 hours from western Nebraska to the Southeastern
Colorado Research Center (SECRC) in Lamar, CO. Steers
were processed over three days, and maintained for the
duration of the study at a commercial feedlot immediately
adjacent to the SECRC. Animals were processed at
receiving and approximately 75 days later, at those times
the following observations were recorded: exit velocity (EV
- exit velocity at receiving; EV_RI - exit velocity at reimplant),
chute score (CS - chute score at receiving; CS_RI
- chute score at re-implant). After 225 days in the feedlot,
animals were harvested and hot carcass weight (HCW, kg),
fat thickness (FAT, cm), ribeye area (REA, cm 2 ), kidney,
pelvic and heart fat (KPH, %), marbling score (MS), and
USDA yield grade (YG) information collected as per
normal carcass data collection procedures. Flight speed was
measured using two infrared electronic triggers to start and
stop an electronic time recording device, the first as the