Department of Animal Science Florida Agricultural
Mimeograph Series No. 62-3 Experiment Station
September, 1961 Gainesville, Florida
A COMPARISON OF LOIN EYE AREAS FROM THE LEFT
AND RIGHT SIDES OF PORK CARCASSES _/
J. W. Carpenter, A. Z. Palmer and H. D. Wallace 2
Loin eye area is a measurement presently used as an indication of
meatiness in pork carcasses; other criteria used in evaluating car-
casses are length and average back fat thickness. Certification stand-
ards for meat type sires and dams require that carcasses of tested
progeny meet minimal loin eye size and carcass length and be properly
finished. The desirability of these carcass characteristics have been
further emphasized through pork carcass shows throughout the United
States. With such an emphasis being placed on loin eye area, it is
important that the measurement be accurate if it is to be used with
confidence in selection of breeding stock and if it is to be used as
a guide to feeding and management of growing-finishing hogs.
Lasley and Kline (1957), reporting on splitting and cutting er-
rors encountered in swine carcass evaluation, found a right-left loin
eye area repeatability of 0.85 which was considered rather low com-
pared to the 0.97 and 0.99 for average fat back thickness and average
length, respectively. Butler, et al. (1956) reported a significant
difference between right and left rib eye areas in beef carcasses and
explained the difference as possibly due to a consistent difference
in technique in separating the fore and hindquarter.
The purpose of this study was to compare the loin eye areas from
the left and right sides of pork carcasses assuming equal size left
and right loin eye areas, differences found could be attributed to
splitting, cutting and measuring errors; this study was undertaken to
provide information as to the magnitude of these sources of variation.
The paired right and left loins of 174 barrow and gilt carcasses,
weighing from 120 to 160 pounds, were cut and measured in the Univer-
sity Meats Laboratory. The loins were removed from the carcasses by
the procedure outlined in the Fourth Annual Reciprocal Meats Conference
1/ The assistance of Mrs. Norma Bowles and Mr. Richard Newman, Labora-
tory Assistants, Animal Science Department, University of Florida,-'--...
2/ Carpenter, Assistant Animal Husbandman; Palmer, Associate'Animal
Husbandman; Wallace, Animal Husbandman; Animal Science Department,
University of Florida, Gainesville, Florida.
Proceedings (1951). One person removed and cut all loins. The un-
trimmed loin was placed chine side down on the band saw table and its
lumbar vertebra cut half-way between the 10th and lith ribs. The cut
was continued through the loin perpendicular to the long axis of the
L.. dorsi muscle. Tracings were made of the eye muscle on the exposed
face of the loin anterior to the 1lth rib before removal of the fat
back. Loin eye area was measured by a compensating polar planimeter,
from the outline tracing of the L. dorsi muscle. Two readings were
made on each tracing and averaged. The mean difference between right
and left sides was tested for statistical significance by use of the
Results and Discussion
The average loin eye area for the right side was 3.751 square
inches compared to 3.753 square inches for the left side. In 85 loin
pairs, or 48.85% of the total, the size of the right eye exceeded the
left. In 82 loin pairs, or 47.12% of the total, the size of the left
eye exceeded the right. In 7 pairs, or 4.03%, the eyes were exactly
equal. The range from the largest to the smallest eye was 6.09
square inches to 2.36 square inches, respectively.
Table I shows the variations in loin eye size arranged for each
one percent increase and the total variation in relation to a standard
4.00 sq. in. loin eye. For example, 7 carcasses, or 4.03% of the
total number of carcasses, varied 0% between sides, thus a 4.00 sq.
in. loin eye would have 0.00 maximum variation. Twenty-two carcasses,
or 12.64%, varied from 0 to 1%. In relation to a 4.00 sq. in. loin
eye, this would have been a variation of from 4.00 sq. in. to 4.04 sq.
in. or a maximum variation of 0.04 sq. in. The percent increase from
the smaller to larger loin eye was computed by the formula:
maximum area minimum area 1
tt may be noted in Table I that in 119 pairs of loins, or in 68.4% of
the total, the maximum variation was less than 5% or less than 0.2 sq.
in. from one side to the other. In 166 pairs of loins, or 95.41% of
the total, variation was less than 10% or 0.4 sq. in. on a 4.00 sq. in.
eye area. This would give a maximum variation of plus or minus 0.2
sq. in. from the average of the two loin eye areas. In 8 pairs of
loins, or in 4.59% of the total observations, the maximum variation
was above 10%; 2 pairs varied more than 19%. Most of the widely vary-
ing loin eyes were made on small eyes from the smaller carcasses;
therefore, the percent of variation was"magnified.
Differences between left and right loin eye areas may have been
I. Bilateral asymmetry--The L. dorsi muscle could be developed
more on one side than on the other.
VARIATIONS IN LOIN EYE SIZE OF PAIRED PORK LOINS
No. Percent Largest Varied From
of Carcasses of Carcasses The Smallest Between:
Percent In sq. in. based
on a 4.00" loin eye
7 4.03 0-0 4.00-4.00
22 12.64 0-1 4.00-4.04
30 17.24 1-2 4.00-4.08
30 17.24 2-3 4.00-4.I'2
19 10.92 3-4 4.00-4.16
11 6.32 4-5 4.00-4.20
12 6.90 5-6 4.00-4.24
8 4.60 6-7 4.00-4.28
13 7.47 7-8 4.00-4.32
8 4.60 8-9 4.00-4.36
6 3.45 9-10 4.00-4.40
2 .1.50 10-11 4.00-4.44
S0.57. 11-12 .4.00-4.48
2 1.15 12-13 4.00-4.52
I 0.57 13-14 4.00-4.56
I 0.57 19-20 4.00-4.80
0.57. 20-21 4.00-4.84
2. Solitting error--Off center splitting of the backbone often,
results in leaving all the chine bones on one side and cutting into
the loin eye on the other.
3. Cutting procedure--If the loin eye is cut in
than exactly perpendicular to the long axis of.the L.
the size of the eye to be traced will be enlarged.
any manner other
4. Cutting oosition--The L. dorsi is smallest immediately over
the rib and enlarges or spreads between the ribs. If the eys issec-
tioned half-way between the ribs, the area will be greater than if
sectioned slightly off center.
Firmness of lean and fat--In some carcasses, the lean and
so soft and watery that the eye will not hold its shape,making
6. Tracing errors--Consistently tracing the inside or the out-
side of the thin membrane that surrounds the eye will give some
variation to the size of the eye tracing.
7. Measuring error--This is probably the smallest error en-
countered; however, following the inside, outside or crossing the
pencil traced outline will give a variation in area as measured by
One or more of the above sources of error singly or combined
could have caused the variations found in this study.
Since the area of the loin eye is used so extensively in evalua-
ting research animals as well as in swine certification, it is extremely
important that the sources of error outlined above be controlled as
The left and right loins of 174 barrow and gilt carcasses were
cut between the 10th and 11th ribs and the area of the loin eyes mea-
sured. In 85 carcasses, the right side had the largest loin eye area,
whereas 82 carcasses had larger loin eye areas in the left side. In
7 carcasses the loin eye areas of the left and right sides were the
same. Differences between left and right loin eye areas were not sig-
nificant even though in some instances differences were appreciable.
Errors or differences were large enough to merit further consideration
of means to eliminate splitting errors, cutting procedure, cutting
position, tracing errors and measuring errors.
Butler, 0. D., M. J. Garber and R. L. Smith. 1956. Beef Carcass
Composition and Yield of Wholesale Cuts as Estimated From Left
and Right Sides. J. Animal Sci. 15:891.
Lasley, E. L. and E. A. Kline. 1957. Splitting and Cutting Errors
in Swine Carcass Evaluation. J. Animal Sci. 16:485.
Report of the Pork Carcass Evaluation Committee, 1951. Cutting
Procedure, Proc. 4th Ann. Reciprocal Meat Conf. 120.