Evaluation of Columbia, USMARCComposite, Suffolk, and Texel Rams as
Terminal Sires in an Extensive Rangeland
Production System
Gregory S. Lewis
USDA, ARS, U.S. Sheep Experiment Station Dubois, ID
David R. Notter
Virginia Tech, Blacksburg
Numbers of lambs weaned per ewe mated for Rambouillet ewes
mated to Columbia, Composite, Suffolk, and Texel rams.
Differences among the sire breeds are not statistically significant.
1.50
1.45
1.40
1.35
1.30
Lambs weaned per ewe lambing
Columbia
Composite
Lambs weaned per ewe mated
Suffolk
Texel
Survival functions from birth to weaning for lambs sired by Columbia, Composite,
Suffolk, and Texel rams, and adjusted to a lamb born in 2007 to a 3-yr-old ewe.
Sire breeds that do not share a common letter differed (P < 0.05) for survival rate.
Body weights at birth, weaning, and 90 days postweaning for lambs sired by
Columbia, Composite, Suffolk, and Texel rams. Values within shaded columns are
birth weights and gains during the pre- and postweaning periods
160
138.8
131.3
148.9
131.1
140
Body weight, lb
120
60.5
53.7
52.4
73.4
72.9
76.3
70.7
11.7
11.6
12.1
11.6
Columbia
Composite
Suffolk
Texel
48.8
100
80
60
40
20
0
Sire breed
Birth wt
Pre-weaning gain
Postweaning gain
Ultrasound backfat thickness for ewe and wether lambs sired by Columbia,
Composite, Suffolk, and Texel rams at 90 days postweaning, or 110 or 132 pounds
live weight . Horizontal lines designate boundaries between Yield Grades 2 and 3
or 3 and 4
0.45
Ultrasound backfat thickness, in
0.40
YG 3/4
0.35
0.30
YG 2/3
0.25
0.20
YG 1/2
0.15
0.10
0.05
0.00
90 d postweaning
Columbia
110 pounds
Composite
Suffolk
132 pounds
Texel
Carcass backfat and body wall thicknesses for wether lambs sired by Columbia,
Composite, Suffolk, and Texel rams at age- or weight-constant endpoints. Horizontal
line is the boundary for carcass backfat between Yield Grades 2 and 3
Carcass backfat or body wall thickness, in
1.00
0.80
0.60
0.40
YG 2/3
0.20
0.00
Age-constant backfat Wt-constant backfat
Columbia
Composite
Age-constant body
wall
Suffolk
Texel
Wt-constant body
wall
Ultrasound loin muscle area for ewe and wether lambs sired by Columbia,
Composite, Suffolk, and Texel rams at 90 days postweaning, 132 pounds live
weight, or 0.25 inches of backfat
Ultrasound loin muscle area, in2
2.70
2.60
2.50
2.40
2.30
2.20
2.10
2.00
90 d postweaning
132 pounds
0.25 inches backfat
Endpoint
Columbia
Composite
Suffolk
Texel
Carcass loin muscle area for wether lambs sired by Columbia, Composite, Suffolk,
and Texel rams at age- or weight-constant endpoints
2.70
Carcass loin muscle area, in2
2.65
2.60
2.55
2.50
2.45
2.40
2.35
2.30
2.25
Age-Constant
Wt-constant
Endpoint
Columbia
Composite
Suffolk
Texel
Relative value of gain:feed ratio, %
Relative values for gain:feed ratio (overall average = 100; higher values indicate
more efficient growth) for lambs sired by Columbia, Composite, Suffolk, and
Texel rams at 90 days postweaning, 132 pounds live weight, or 0.25 inches of
backfat
120
110
100
90
80
90 d postweaning
Columbia
132 pounds
Composite
Suffolk
0.25 inches backfat
Texel
Residual feed intake for lambs sired by Columbia, Composite, Suffolk, and Texel rams at 90
days postweaning, 132 pounds live weight, or 0.25 inches of backfat. Low values are
superior, and indicate that less feed was required given observed body weights and average
daily gains
Residual feed intake, pounds
25.00
Columbia-sired lambs required over 15 lb
more feed than expected based on
observed body wt and growth rates
20.00
15.00
10.00
5.00
0.00
-5.00
-10.00
90 days
Columbia
132 pounds
Composite
Suffolk
0.25 inches backfat
Texel
Residual gain for lambs sired by Columbia, Composite, Suffolk, and Texel rams at 90
days postweaning, 132 pounds live weight, or 0.25 inches of backfat. Higher values
are superior, and indicate more rapid gains at similar body weights and levels of feed
intake
3.00
Suffolk-sired lambs gained 2+ lb more
than expected based on their observed
body wt and feed intake
2.50
Residual gain, lb
2.00
1.50
1.00
0.50
0.00
-0.50
-1.00
-1.50
-2.00
90 days
Columbia
132 pounds
Composite
Suffolk
0.25 inches backfat
Texel
Alternative measures of feed efficiency intake for lambs sired by Columbia,
Composite, Suffolk, and Texel rams at 90 days on test. Values have been adjusted to
equalize the scales, and values of RFI are inverted. Therefore, positive values are
always superior.
“Feed efficiency” measurement
40
Relative efficiency of Texel vs.
Suffolk is different for RFI than for
other estimates of efficiency
30
20
10
0
-10
-20
Gain:feed (scaled)
Columbia
RFI (inverted)
Composite
RNG (scaled)
Suffolk
Texel
Net returns, $
Cumulative residual feed intake across
days on study by lamb sire breed
Selling on a Lamb Pricing Grid
Yield Grade / Backfat Thickness (in)
Carcass wt,
lb
1
(< 0.16)
55-65
75-85
85
3
(0.26-0.36)
- $5 / cwt
<55
65-75
2
(0.16-0.26)
Base
+ $12/cwt
Base
- $20/cwt
4
(0.36-0.46)
5
(>0.46)
- $15 / cwt -$35 / cwt
-$10 / cwt -$30 / cwt
- $30 /cwt - $50 /cwt
Selling on a Lamb Pricing Grid
USSES Terminal Sired Lambs:
4 sire breeds (CO, C3, SU, TX) mated to Rambouillet ewes.
Harvest lambs at wts between 120 and 150 lb.
Where do they fit the Grid?
Yield Grade / Backfat Thickness (in)
Carcass wt,
lb
<55
55-65
65-75
75-85
85
1
(< 0.16)
2
(0.16-0.26)
3
(0.26-0.36)
- $5 / cwt (1%)
+ $12/cwt
Base
(70%)
(23%)
Base (2%)
- $20/cwt
4
(0.36-0.46)
5
(>0.46)
- $15 / cwt -$35 / cwt
-$10 / cwt -$30 / cwt
(4%)
- $30 /cwt - $50 /cwt