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Breed
performance records of prolificacy (lambing %), growth rates
of lambs to 8 & 21 weeks and back scanning to assess
leaness have been carried out in the flock since 1994.
Prolificacy
has fallen from a high of 218% in 1994 to 182% in 2001.
The reason for this is not clear.
The mean growth rate (daily weight gain to 8 weeks) for
ram lambs is 370g and for ewe lambs it is 360g.
In
2002 all the lambs were backscanned at 21 weeks. No such
measurements were possible in 2001due to FMD
Selection
of ram lambs for retaining in the flock depends on 3 criteria:
- genotype
R1,
- good
breed conformation and character,
- high
scheme index (>50% scheme percentile).
Only
2 lambs JER.Z37 (Zeb) and JER.Z44 (Zac) fulfilled all
criteria
Zeb and Zac
|
Feature
|
JER.Z37
|
JER.Z44
|
Rumwell
lambs
|
all
SRS lambs
|
| 8
week wt. kg |
29.5 |
27.0 |
23.2 |
26.2 |
| growth
rate g/day |
490 |
420 |
370 |
405 |
| scan
wt. kg |
62.5 |
68.0 |
47.5 |
47.7 |
| muscle
depth mm |
30.0 |
30.7 |
22.3 |
26.1 |
| fat
depth mm |
3.00 |
2.90 |
2.08 |
2.23 |
| EBVs
scan kg |
+3.05 |
+5.00 |
+1.92 |
+1.93 |
| muscle
mm |
+0.83 |
+1.53 |
+0.56 |
+0.53 |
| fat
mm |
+0.25 |
+0.20 |
-0.05 |
+0.02 |
| SI |
146 |
204 |
141(mean) |
135(mean) |
Comparison
of ram lambs 2002
Selection
of ewe lambs is based on breed conformation and character,
scheme index, and genotype R1 or R4. Only 2 ewe lambs out
of 21 were typed R4.
There
were some excellent ewe lambs born in 2002.
Choice
has been made based on actual measurements of muscle and
fat. The 10 ewe lambs retained this year have muscle >25mm
and fat 3.00mm and very good breed features.
Their SI range is from 85 to 207
Ewe lambs 2002
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