Download A maternal Suffolk Index

A Maternal Breeding Index for Suffolk Sheep
Task: EGENES were asked to develop a maternal index for the Suffolk breed. It was
suggested that this index mimic the Dorset maternal index and include litter size,
maternal ability and eight week weight as the selection criteria. It was requested that
mature size was not used as selection criteria.
Suffolk genetic parameters: Compared with the Dorset breed the genetic parameters
for Suffolk sheep are broadly similar; eight week weight has the same heritability but
larger variation, maternal ability has a smaller heritability with less variance and litter
size born is slightly more heritable with greater variance.
Two indexes were modelled by EGENEs, the second option presented here was a
modification to reflect the differences in the genetic parameters (i.e. it was more Suffolk
specific).
Suffolk Maternal Index
EBV
Index
Relative
Genetic
weight emphasis (%)
response*
8 week weight
0.37
45
0.623
Scan weight
0
0
1.013
Muscle depth
0
0
0.223
Fat depth
0
0
0.108
Maternal ability
1.57
45
0.617
Mature size
0
0
0.494
Litter size
7.15
10
0.138
CT_lean
0
0
0.249
CT_fat
0
0
0.213
CT_musc
0
0
0.245
* Gain in EBVs per generation when the selection intensity is equal to 1 standard
deviation (approximately the best 38% of animals selected).
A Base for the New Index
The Suffolk Terminal Sire Index is an economic index.
A “desired gains” approach has been applied to the construction of the Suffolk Maternal
Index and this index will be rescaled to reflect a mean of 100 and standard deviation of
40 index points for lambs born in 2005.
The range of index values is relatively wide. Selecting 2010/2011 born animals on the
basis of the new Maternal Index will result in the top 10% expressing maternal indexes
of 222 (with some having indexes exceeding 300 points). The lowest 10% have indexes
averaging roughly 70 index points.