Does selecting for finer wool result in higher incidence
of creeping bellies in Dohne Merino sheep?
P.
1
Naidoo ,
JJ
1,#
Olivier , J
2
Morris
and S.W.P.
1,2
Cloete
1Directorate:
Animal Sciences, Western Cape Department of Agriculture; 2Department of Animal Sciences, Stellenbosch University.
Corresponding author: [email protected]
Introduction
The breeding objective of the Dohne Merino breed is to decrease fibre diameter while maintaining fleece
weight. It was postulated that selection for finer wool would increase the incidence of creeping belly and as a
result decrease the financial value of the fleece.
Materials & Methods
Data (n = 2290) used was collected from the Dohne Merino
stud at the Mariendal experimental farm of the University of
Stellenbosch
A 7-trait linear-threshold animal model was fitted to the
data.
Objectively assessed production traits (linear traits): live
weight (LW); clean fleece weight (CFW), mean fibre
diameter (MFD), staple length (SL) and coefficient of
variation of fibre (CV)
Subjectively scored variables (binary traits): creeping belly
score (CBS) and wool quality scores (WQS)
Fixed effects: Production year, sex, birth type and dam age
Random effects: direct, additive animal
THRGIBBS1F90 and POSTGIBBSF90 software was used for the
analyses as the data contained both categorical and
continuous traits
Results
Table 1. Descriptive statistics for live weight (LW), clean
fleece weight (CFW), mean fibre diameter (MFD), staple
length (SL), coefficient of variation of MFD (CV) and
subjectively appraised creeping belly (CBS) and wool
quality scores (WQS) of Dohne Merino yearlings
Table 2. Direct additive and residual variance components
(2a and 2e respectively) and (co) variance ratios for clean
fleece weight (CFW), mean fibre diameter (MFD), staple
length (SL) and subjectively appraised creeping belly (CBS)
and quality scores (WQS) of Dohne Merino yearlings
DISCUSSION
The frequency of animals judged to have creeping bellies (18 %)
was twice as much as those with poor wool quality (9 %).
Creeping belly has a low h2 of 0.16  0.04 while WQS was highly
heritable at 0.43  0.15.
Sheep with acceptable WQS would generally have stronger
fleeces (WQS and MFD 0.36  0.14).
Sheep with acceptable WQS scores tend to have poorer CBS
(WQS and CBS -0.55  0.27)
Lower CFW can result in a higher incidence of creeping bellies
CONCLUSIONS
This study found that selection for finer
wool with high wool quality can result in
a higher incidence of creeping belly.
It is therefore important to place a cap
on clean fleece weight selection and
monitor the incidence of creeping
belly.